HK40090710A - Direct-current power distribution in a control system - Google Patents

Description

DC power distribution in the control system

Cross-references to related applications

This application claims the benefit of Provisional U.S. Patent Application No. 63/078,976, filed September 16, 2020, and Provisional U.S. Patent Application No. 63/105,033, filed October 23, 2020, the disclosures of which are incorporated herein by reference in their entirety.

Background Technology

Typical blinds (such as roller blinds, fabric blinds, Roman blinds, and/or Venetian blinds) are installed in front of windows or openings to control the amount of light entering the user's environment and/or provide privacy. The covering material on the blinds (e.g., blackout fabric) can be adjusted to control the amount of daylight entering the user's environment and/or provide privacy. The covering material can be manually controlled and/or automatically controlled using an electrically driven system to achieve energy savings and/or improve occupant comfort. For example, the covering material can be raised to allow light into the user's environment and allow for reduced use of lighting systems. The covering material can also be lowered to reduce the occurrence of solar glare.

Summary of the Invention

A control system may include a power bus for charging (e.g., trickle charging) internal energy storage elements in a control device of the control system. For example, the control device may be motorized blinds configured to adjust the position of covering material to control the amount of daylight entering a space. The system may include a bus power supply capable of generating a direct current (DC) voltage on the power bus. The bus power supply may generate a bus current to power one or more devices connected to the power bus. The bus power supply may include an overpower protection circuit configured to disconnect the bus power supply (e.g., the power converter of the bus power supply) from the power bus. For example, the overpower protection circuit may be configured to disconnect the bus power supply if the bus current exceeds a threshold for a certain period of time. In some examples, the bus power supply may be configured with multiple thresholds, each with a different associated time limit. The power bus may extend from the bus power supply around the perimeter of a building's floors and may connect to all of the motorized blinds on that floor (e.g., in a daisy-chain configuration). Wiring the power bus in this way can significantly reduce installation labor and wiring costs, as well as the possibility of wiring errors.

Each control device may be configured to control when the internal energy storage element is charged from the bus voltage. For example, each control device may be configured to determine when to charge the internal energy storage element from the bus voltage in response to a message received via a communication circuit. Each control device may be configured to transmit a message including the storage level of the internal energy storage element. The storage level of the internal storage element may be a percentage of its maximum capacity (e.g., 60% of the maximum storage capacity) or a percentage of its maximum voltage, or a preset voltage level of the internal storage element.

Drive units (e.g., motor drive units, such as those for motorized curtains) can be used in a power distribution system, wherein the power distribution system may include the bus power supply and multiple drive units. The drive unit may include power limiting circuitry configured to conduct current from the power bus and generate a supply voltage. The drive unit may include load circuitry (e.g., motor drive circuitry) configured to receive the supply voltage and control the power delivered to the electrical load. The drive unit may include control circuitry configured to determine, based on the power required by the drive unit, the cumulative total power required by the multiple drive units, and the power capacity of the bus power supply, an allocated amount of power that the drive unit can consume from the power bus. The control circuitry may be configured to control the power limiting circuitry to consume the allocated power from the power bus. For example, the control circuitry may be configured to determine a proportional power amount for the drive unit based on the power required by the drive unit and the cumulative total power required by the multiple drive units, and may be configured to determine the allocated power amount based on the proportional power amount for the drive unit and the power capacity of the bus power supply. The control circuit can be configured to determine the cumulative total power required by the plurality of drive units based on the magnitude of the current conducted from the plurality of drive units to the power bus.

The drive unit may also include an internal energy storage element configured to store sufficient power for multiple operations of the load circuit. In such an example, the amount of power required by the drive unit may be based on the amount of power required by the load circuit to supply the electrical load and the voltage across the internal energy storage element.

The bus power supply may be configured to provide the bus voltage on the power bus during the on-phase of a periodic time period, and to not provide the bus voltage on the power bus during the off-phase of the periodic time period. In such a case, the control circuitry may be configured to measure the magnitude of the bus voltage across the power bus during the off-phase of the periodic time period, wherein the magnitude of the bus voltage across the power bus may indicate the cumulative total power required by the plurality of drive units.

For example, the control circuitry may be configured to conduct a power-demand current to the power bus during the off portion of the periodic time period, wherein the magnitude of the power-demand current may be proportional to the amount of power required by the drive unit. The control circuitry may be configured to measure the magnitude of the bus voltage across the power bus during the off portion of the periodic time period. The control circuitry may be configured to estimate a proportion of the power capacity of the bus power supply that the drive unit can consume during the next on portion of the periodic time period based on the power required by the drive unit and the magnitude of the bus voltage across the power bus during the off portion of the periodic time period. The control circuitry may be configured to control the power limiting circuitry to consume the allocated power from the power bus during the next on portion of the periodic time period, wherein the allocated power may be determined based on the proportion that the drive unit can consume multiplied by the power capacity of the bus power supply. In some examples, the control circuitry may be configured to determine the amount of power required by the drive unit based on the power required for the drive unit to supply power to the electrical load, to charge the internal energy storage element of the motor drive unit, and the standby power consumption of the motor drive unit.

The control circuitry can be configured to signal the required power amount to the bus power supply before controlling the power limiting circuitry to consume the allocated power from the power bus.

The drive unit may be part of a system comprising multiple drive units and a bus power supply, the bus power supply including a power converter configured to generate the bus voltage on the power bus, wherein the bus power supply may have a power capacity defining a maximum amount of power that the bus power supply can deliver through the power bus. The bus power supply may be characterized by a nominal power capacity defining a nominal power threshold, which, when equal to or below the nominal power threshold, allows the bus power supply to supply power to the multiple drive units indefinitely, wherein the nominal power threshold may be less than the maximum amount of power defined by the power capacity of the bus power supply. The bus power supply may be configured to continuously supply power to the power bus when equal to or below the nominal power threshold without being interrupted or disconnected by the bus power supply's overpower protection circuitry. The bus power supply may be configured to supply power to the multiple drive units at one or more increased power capacities greater than the nominal power capacity for a period of time up to but not longer than a corresponding predetermined increased power period.

The bus power supply may include a power converter circuit and an over-power protection circuit. The over-power protection circuit may be configured to disconnect the bus voltage from the power bus in response to the output power of the power converter circuit exceeding a first power increase threshold for a first power increase time period, and may be configured to disconnect the bus voltage from the power bus in response to the output power of the power converter circuit exceeding a second power increase threshold for a second power increase time period.

The bus power supply may include a variable resistor, and the bus power supply may be configured to adjust the variable resistance of the variable resistor to adjust the allocated power estimated by each of the motor drive units on the power bus. An increase in the variable resistance may cause the control circuitry of each of the plurality of drive units to determine that the cumulative total power required by the plurality of drive units has increased.

A load control system for controlling multiple electrical loads may include a bus power supply and multiple drive units (e.g., motor drive units). The bus power supply may include a power converter. The bus power supply may be configured to generate a bus voltage on the power bus during an on-phase portion of a periodic time period and to not generate the bus voltage on the power bus during an off-phase portion of the periodic time period. The bus power supply may have a power capacity that defines a maximum amount of power that the bus power supply can deliver through the power bus.

The drive unit may include power limiting circuitry configured to conduct current from the power bus and generate a supply voltage. The drive unit may include internal energy storage elements and/or load circuitry. The load circuitry may be configured to receive the supply voltage and control the power delivered to the electrical load. The drive unit may include control circuitry configured to determine the amount of power required by the drive unit to power the electrical load and charge the internal energy storage elements. The control circuitry may be configured to conduct a power-demand current to the power bus during the off portion of the periodic time period. The magnitude of the power-demand current may be proportional to the amount of power required by the drive unit. The control circuitry may be configured to measure the magnitude of the bus voltage across the power bus during the off portion of the periodic time period. The control circuitry may be configured to estimate a proportion of the power capacity of the bus power supply that the drive unit can consume during the next on portion of the periodic time period based on the power required by the drive unit and the magnitude of the bus voltage across the power bus during the off portion of the periodic time period. The control circuitry can be configured to control the power limiting circuitry to consume the proportional amount of power from the power bus during the next on-phase of the periodic time period. The allocated power amount can be determined based on the proportional amount that the drive unit can consume multiplied by the power capacity of the bus power supply. The magnitude of the bus voltage across the power bus can represent the cumulative total power required by the plurality of drive units.

A bus power supply for use in a load control system for controlling multiple electrical loads may include a power converter circuit and an overload protection circuit. The power converter circuit may be configured to generate a DC bus voltage on the DC power bus of the load control system. The overload protection circuit may be configured to disconnect the power converter circuit from the power bus in response to a bus current exceeding a first current threshold for a first time period or exceeding a second current threshold for a second time period. In some examples, the overload protection circuit may be configured to de-conduct a controllable conductive device to disconnect the power converter circuit from the power bus. For example, the controllable conductive device may include two field-effect transistors (FETs) in an anti-series configuration. The first current threshold may be less than the second current threshold, and the first time period may be longer than the second current threshold.

The overcurrent protection circuit may include a first comparator and a second comparator, the first comparator being configured to compare the bus current with a first current threshold, and the second comparator being configured to compare the bus current with a second current threshold. The overcurrent protection circuit may also include a first timer and a second timer, the first timer being configured to determine whether a first time period has elapsed, and the second timer being configured to determine whether a second time period has elapsed. The overcurrent protection circuit may include a latch circuit configured to disconnect the power converter circuit from the power bus. The overcurrent protection circuit may be further configured to momentarily disconnect the power converter circuit from the power bus when the bus current exceeds a momentary trip current.

A bus power supply configured to provide a bus voltage to multiple devices may include a first controllable switching circuit and a second controllable switching circuit. The second controllable switching circuit may be coupled between a connection point of the first controllable switching circuit and a common terminal of a circuit via a sensing resistor. The bus power supply may include control circuitry configured to: for an on portion of a periodic time period, turn on the first controllable switching circuit and turn off the second controllable switching circuit to provide the bus voltage on the power bus during the on portion of the periodic time period; and for an off portion of the periodic time period, turn off both the first and second controllable switching circuits to not provide the bus voltage on the power bus during the off portion of the periodic time period. The control circuitry may be configured to measure the total voltage across the power bus during the off portion of the periodic time period and determine the total power requirement of the multiple devices based on the measurement results.

The bus power supply may include a first power connector and a second power connector. The first power connector is used to receive input voltage from an external power supply, and the second power supply is configured to connect to the power bus, wherein the bus is configured to be electrically coupled to the plurality of devices. A first controllable switching circuit may be coupled between the output of the power converter and the second power connector. A second controllable switching circuit may be coupled between the connection point of the first controllable switching circuit and the second power connector and a common terminal of a circuit through a sensing resistor. The second controllable switching circuit and the sensing resistor may be coupled in parallel between the terminals of the second power connector. The external power supply may include an AC power supply for generating AC trunk line voltage.

The sensing resistor may include a variable resistor. The control circuitry may be configured to adjust the variable resistance of the variable resistor to adjust the amount of power delivered by the bus power supply through the power bus during the on-phase of the periodic time period. In some examples, the bus power supply may include a power converter circuit, and the bus power supply may have a power capacity that defines a maximum output power of the power converter circuit. In such examples, the control circuitry may be configured to adjust the variable resistance of the variable resistor to adjust the magnitude of the output power of the power converter circuit. The control circuitry may be configured to adjust the variable resistance of the variable resistor to adjust the total power demand of the plurality of devices. The bus power supply may be characterized by a nominal power capacity that defines a nominal power threshold, and the bus power supply may supply power to the plurality of devices indefinitely when equal to or below the nominal power threshold. The bus power supply may be configured to adjust the variable resistance of the variable resistor to allow the plurality of devices to consume an amount of power on the power bus greater than (e.g., and/or less than) the nominal power threshold.

The bus power supply includes a current source and can be configured to conduct current to the power bus during the off portion of the periodic time period to adjust the amount of power consumed by the plurality of devices.

The bus power supply can be configured to supply power to the plurality of devices at one or more increased power capacities greater than the nominal power capacity for a period of time up to but not longer than a corresponding predetermined increased power period. For example, the bus power supply may include an overpower protection circuit configured to disconnect the bus voltage from the power bus in response to an overpower condition. A first controllable switching circuit may be coupled between the output of the overpower protection circuit and the power bus. The bus power supply can continuously supply power to the power bus at or below the nominal power threshold without being interrupted or disconnected by the overpower protection circuit. The bus power supply may include a power converter circuit. The overpower protection circuit can be configured to disconnect the bus voltage from the power bus in response to the output power of the power converter circuit exceeding a first increased power threshold for a first increased power period, and can be configured to disconnect the bus voltage from the power bus in response to the output power of the power converter circuit exceeding a second increased power threshold for a second increased power period.

The bus power supply may include a power converter circuit and an overcurrent protection circuit. The power converter circuit is configured to generate a supply voltage, and the overcurrent protection circuit is configured to receive the supply voltage from the power converter circuit and provide the bus voltage on the power bus. The overcurrent protection circuit may be configured to disconnect the power converter circuit from the power bus in response to the supply voltage exceeding a first power threshold for a first time period, and/or in response to the supply voltage exceeding a second power threshold for a second time period, wherein the first power threshold is less than the second power threshold, and the first time period is longer than the second time period. The overcurrent protection circuit may be further configured to momentarily disconnect the power converter circuit from the power bus when the bus current exceeds a maximum power threshold.

Attached Figure Description

Figure 1 is a simplified block diagram of a load control system with a load control device and an electric curtain.

Figures 2A to 2C are plan views of a DC power distribution system used in a control system.

Figure 3 is a block diagram of an exemplary motor drive unit for an electric curtain.

Figure 4A is a block diagram of an exemplary bus power supply used in the DC power distribution system of a load control system.

Figure 4B is a block diagram of an exemplary overpower protection circuit for a bus power supply used in a DC power distribution system of a load control system.

Figure 4C is a block diagram of an exemplary overpower protection circuit for a bus power supply used in a DC power distribution system of a load control system.

Figure 4D shows an example of the increased power threshold and associated increased power time period of the overpower protection circuit.

Figure 5 shows an example of a waveform illustrating the operation of a bus power supply connected to the power bus of a DC power distribution system.

Figure 6 is a block diagram of an exemplary motor drive unit for an electric curtain.

Figure 7 shows an example of a control device used in a DC power distribution system.

Figure 8 shows an example of waveforms illustrating the operation of two motor drive units connected to the power bus in a DC power distribution system.

Figure 9 is a flowchart of an exemplary program that can be executed by the control circuit of the motor drive unit.

Figure 10A is a flowchart of an exemplary program that can be executed by a bus power supply.

Figure 10B is a flowchart of an exemplary program that can be executed by a bus power supply.

Figure 11 is a block diagram of an exemplary DC power distribution system.

Figure 12 is an exemplary waveform showing the output power of the bus power supply.

Detailed Implementation

Figure 1 is a simplified diagram of an exemplary load control system for controlling the amount of power delivered from an alternating current (AC) power source (not shown) to one or more electrical loads. The load control system 100 may include a system controller 110 (e.g., a load controller or central controller) operable to transmit and/or receive digital messages via wired and/or wireless communication links. For example, the system controller 110 may be coupled to one or more wired control devices via a wired digital communication link 104. The system controller 110 may be configured to transmit and/or receive wireless signals (e.g., radio frequency (RF) signals 106) to communicate with one or more wireless control devices. The load control system 100 may include a plurality of control source devices and/or a plurality of control target devices for controlling the electrical load. The control source devices may be input devices operable to transmit digital messages configured to control the electrical load via the control target devices. For example, the control source devices may transmit digital messages in response to user input, occupancy/vacancy status, changes in measured light intensity, and/or other input information. The control target device can be a load control device configured to receive digital messages and control a corresponding electrical load in response to the received digital messages. A single control device of the load control system 100 can operate as either a control source device or a control target device. The system controller 110 can be configured to receive digital messages from the control source device and transmit digital messages to the control target device in response to the digital messages received from the control source device. The control source device and the control target device can also, or alternatively, communicate directly.

The load control system 100 may include load control devices, such as a dimmer switch 120, for controlling the lighting load 122. The dimmer switch 120 may be adapted for wall mounting in a standard electrical box. The dimmer switch 120 may include a desktop or plug-in load control device. The dimmer switch 120 may include a toggle actuator 124 (e.g., a button) and/or an intensity adjustment actuator 126 (e.g., a rocker switch). Continuous actuation of the toggle actuator 124 can toggle (e.g., turn off and on) the lighting load 122. Actuation of the upper or lower portion of the intensity adjustment actuator 126 can increase or decrease the amount of power delivered to the lighting load 122, respectively, and can increase the intensity of the lighting load from a minimum intensity (e.g., approximately 1%) to a maximum intensity (e.g., approximately 100%) or decrease it from the maximum intensity to the minimum intensity. The dimmer switch 120 may also include a plurality of visual indicators 128, such as light-emitting diodes (LEDs), that can be arranged in a linear array and illuminated to provide feedback on the intensity of the lighting load 122. The dimmer switch 120 may be configured to receive digital messages from the system controller 110 via an RF signal 106 and control the lighting load 122 in response to the received digital messages. The dimmer switch 120 may also, or alternatively, be coupled to a wired digital communication link 104. Examples of wall-mounted dimmer switches are described in more detail in U.S. Patent No. 5,248,919, entitled “LIGHTING CONTROL DEVICE,” published September 28, 1993, and U.S. Patent No. 9,679,696, entitled “WIRELESS LOAD CONTROL DEVICE,” published June 13, 2017, the entire disclosure of which is hereby incorporated by reference.

The load control system 100 may also include one or more remotely positioned load control devices, such as a light-emitting diode (LED) driver 130 (e.g., an LED light engine) for driving a corresponding LED light source 132. The LED driver 130 may be remotely positioned within a lighting fixture, such as the corresponding LED light source 132. The LED driver 130 may be configured to receive digital messages from the system controller 110 via a digital communication link 104 and control the corresponding LED light source 132 in response to the received digital messages. The LED driver 130 may be coupled to a separate digital communication link (such as a Digital Addressable Lighting Interface (DALI) communication link), and the load control system 100 may include a digital lighting controller coupled between the digital communication link 104 and the separate communication link. The LED driver 132 may include internal RF communication circuitry or may be coupled to external RF communication circuitry (e.g., mounted externally to the lighting fixture, such as to the ceiling) for transmitting and/or receiving RF signals 106. The load control system 100 may also include other types of remotely positioned load control devices, such as electronic dimming ballasts for driving fluorescent lamps.

The load control system 100 may also include multiple daylight control devices, such as motorized blinds, like motorized roller blind 140, to control the amount of daylight entering a building where the load control system may be installed. The motorized roller blind 140 may include a covering material (e.g., curtain fabric 142). The covering material may be wound around a roller tube to raise and/or lower the curtain fabric 142. The motorized roller blind 140 may include a motor drive unit 144 (e.g., an electronic drive unit). The motor drive unit 144 may be located inside the roller tube of the motorized roller blind. The motor drive unit 144 may be coupled to a digital communication link 104 for transmitting and/or receiving digital messages. The motor drive unit 144 may include control circuitry. The control circuitry may be configured to adjust the position of the curtain fabric 142, for example, in response to digital messages received from a system controller 110 via the digital communication link 104. Each of the motor drive units 144 may include memory for storing association information for association with other devices and/or instructions for controlling the motorized roller blind 140. The motor drive unit 144 may include internal RF communication circuitry. The motor drive unit 144 may also, or alternatively, be coupled to an external RF communication circuit (e.g., located outside the roller tube) for transmitting and/or receiving RF signals 106. The load control system 100 may include other types of daylight control devices, such as, for example, honeycomb blinds, fabric blinds, Roman blinds, soft Venetian blinds, pleated blinds, tension roller blind systems, electrochromic or smart windows and/or other suitable daylight control devices.

The load control system 100 may include one or more other types of load control devices, such as screw-in luminaires including dimmer circuitry and incandescent or halogen lamps; screw-in luminaires including ballasts and compact fluorescent lamps; screw-in luminaires including LED drivers and LED light sources; electronic switches, controllable circuit breakers, or other switching devices for turning the appliance on and off; plug-in load control devices, controllable electrical outlets, or controllable power boards for controlling one or more plug-in loads; motor control units for controlling motor loads (such as ceiling fans or exhaust fans); drive units for controlling motorized curtains or projection screens; and motorized internal or external blinds. Leaflets; thermostats for heating and/or cooling systems; temperature control devices for controlling setpoint temperatures in HVAC systems; air conditioners; compressors; electric kickboard heater controllers; controllable dampers; variable air volume controllers; fresh air intake controllers; ventilation controllers; hydraulic valves for radiator and radiant heating systems; humidity control units; humidifiers; dehumidifiers; water heaters; boiler controllers; pool pumps; refrigerators; freezers; television or computer monitors; cameras; audio systems or amplifiers; elevators; power supplies; generators; chargers, such as electric vehicle chargers; and/or alternative energy controllers.

The load control system 100 may include one or more input devices, such as a wired keypad device 150, a battery-powered remote control device 152, an occupancy sensor 154, a daylight sensor 156, and/or a shadow sensor 158. The wired keypad device 150 may be configured to transmit digital messages to the system controller 110 via a digital communication link 104 in response to actuation of one or more buttons on the wired keypad device. The battery-powered remote control device 152, the occupancy sensor 154, the daylight sensor 156, and/or the shadow sensor 158 may be wireless control devices (e.g., RF transmitters) configured to transmit digital messages to the system controller 110 via an RF signal 106 (e.g., directly to the system controller). For example, the battery-powered remote control device 152 may be configured to transmit digital messages to the system controller 110 via an RF signal 106 in response to actuation of one or more buttons on the battery-powered remote control device 152. Occupancy sensor 154 may be configured to transmit a digital message via RF signal 106 to system controller 110 in response to detecting occupancy and/or vacancy in the space where load control system 100 may be installed. Sunlight sensor 156 may be configured to transmit a digital message via RF signal 106 to system controller 110 in response to detecting varying amounts of natural light intensity. Shade sensor 158 may be configured to transmit a digital message via RF signal 106 to system controller 110 in response to detecting external light intensity from outside the space where load control system 100 may be installed. System controller 110 may be configured to transmit one or more digital messages to load control devices (e.g., dimmer switch 120, LED driver 130, and/or motorized roller blind 140) in response to digital messages received, for example, from wired keypad device 150, battery-powered remote control device 152, occupancy sensor 154, sunlight sensor 156, and/or shade sensor 158. Although the system controller 110 can receive digital messages from the input device and/or transmit digital messages to the load control device for controlling the electrical load, the input device can communicate directly with the load control device for controlling the electrical load.

The load control system 100 may include a wireless adapter device 160 that can be coupled to a digital communication link 104. The wireless adapter device 160 may be configured to receive an RF signal 106. The wireless adapter device 160 may be configured to transmit a digital message to the system controller 110 via the digital communication link 104 in response to a digital message received from a wireless controller via the RF signal 106. For example, the wireless adapter device 160 may retransmit the digital message received from the wireless controller on the digital communication link 104.

Occupancy sensor 154 can be configured to detect occupancy and/or vacancy in a space where load control system 100 may be installed. Occupancy sensor 154 can transmit a digital message via RF signal 106 to system controller 110 in response to detecting occupancy and/or vacancy. System controller 110 can be configured to turn on and off one or more of lighting load 122 and/or LED light source 132 respectively in response to receiving occupancy and vacancy commands. Occupancy sensor 154 can also operate as a vacancy sensor, causing the lighting load to turn off in response to detecting vacancy (e.g., not turn on in response to detecting occupancy).

The daylight sensor 156 can be configured to measure the total light intensity in a space where a load control system is installed. The daylight sensor 156 can transmit a digital message including the measured light intensity to the system controller 110 via an RF signal 106. The digital message can be used to control electrical loads (e.g., the intensity of lighting load 122, motorized curtains 140 for controlling the horizontal height of covering material, and the intensity of LED light source 132) via one or more load control devices (e.g., dimmer switch 120, motor drive unit 144, LED driver 130).

A shadow sensor 158 can be configured to measure the intensity of external light from outside the space where a load control system 100 may be installed. The shadow sensor 158 can be mounted on the facade of a building, such as the exterior or interior of a window, to measure the intensity of external natural light based on the sun's position in the sky. The shadow sensor 158 can detect when direct sunlight shines directly into the shadow sensor 158, when it is reflected onto the shadow sensor 158, or when it is blocked by external means such as clouds or buildings, and can send a digital message indicating the measured light intensity. The shadow sensor 158 can transmit the digital message including the measured light intensity to a system controller 110 via an RF signal 106. The digital message can be used to control electrical loads (e.g., the intensity of lighting load 122, motorized curtains 140 for controlling the horizontal height of covering material, and/or the intensity of LED light source 132) via one or more load control devices (e.g., dimmer switch 120, motor drive unit 144, and/or LED driver 130). The shadow sensor 158 may also be referred to as a window sensor, a cloudy sensor, or a sun sensor.

The load control system 100 may include other types of input devices, such as: temperature sensors; humidity sensors; radiometers; pressure sensors, smoke detectors, carbon monoxide detectors, air quality sensors, motion sensors; safety sensors; proximity sensors; fixture sensors; zone sensors; keypads; kinetic or solar-powered remote controls; key fobs; cellular phones; smartphones; tablet computers; personal digital assistants; personal computers; laptop computers; clocks; audio-visual controllers; safety devices; power monitoring devices (such as power meters, energy meters, utility meters, efficiency meters); central control transmitters; residential; commercial or industrial controllers; or any combination of these input devices. These input devices may transmit digital messages to the system controller 110 via RF signal 106. The digital messages may be used to control electrical loads (e.g., the intensity of lighting load 122, motorized curtains 140 for controlling the horizontal height of covering materials, and/or the intensity of LED light sources 132) via one or more load control devices (e.g., dimmer switches 120, motor drive units 144, and/or LED drivers 130).

System controller 110 can be configured to control load control devices (e.g., dimmer switch 120, LED driver 130, and/or motorized roller blind 140) according to a clock schedule. The clock schedule can be stored in the system controller's memory. The clock schedule can be defined by a user of the system controller (e.g., a system administrator using the programming mode of system controller 110). The clock schedule may include multiple clock events. Clock events may have event times and corresponding commands or presets. System controller 110 can be configured to track the current time and/or date. System controller 110 can issue appropriate commands or presets at the corresponding event time for each clock event.

The load control system 100 may be part of an automated curtain control system. The system controller 110 may control the blackout curtains based on automated curtain control information. For example, automated curtain control information may include the angle of the sun, sensor information, cloud cover, and/or weather data, such as historical and real-time weather data. For example, throughout the calendar day, the system controller 110 of the automated curtain control system may adjust the position of the curtain fabric multiple times based on the estimated position of the sun or sensor information. The automated curtain control system may determine the position of the curtains to affect performance indicators. The automated curtain system may command the system controller 110 to adjust the curtains to the determined position to affect performance indicators. The automated curtain control system may operate according to a clock schedule. Based on the clock schedule, the system controller may change the position of the curtains throughout the calendar day. The clock schedule may be set to prevent sunlight penetration distance from exceeding the maximum distance into interior spaces (e.g., workspaces, transition spaces, or social spaces). The maximum sunlight penetration distance may be set for the user's workspace. The system controller 110 may adjust the position of the curtains based on collected sensor information.

System controller 110 is operable to be coupled to a network (such as a wireless or wired local area network (LAN)) via network communication bus 162 (e.g., an Ethernet communication link), for example, to access the Internet. System controller 110 may be connected to network switch 164 (e.g., a router or Ethernet switch) via network communication bus 162 to allow system controller 110 to communicate with other system controllers to control other electrical loads. System controller 110 may connect to the network wirelessly, for example, using Wi-Fi technology. System controller 110 may be configured to communicate via the network with one or more network devices (such as smartphones, personal computers 166, laptops, tablet devices (e.g., handheld computing devices), wireless communication-enabled televisions, and/or any other suitable wireless communication devices (e.g., Internet Protocol-enabled devices)). Network devices are operable to transmit digital messages to system controller 110 in one or more Internet Protocol packets.

The operation of the load control system 100 can be programmed and/or configured using a personal computer 166 or other network device. The personal computer 166 can execute graphical user interface (GUI) configuration software to allow a user to program how the load control system 100 can operate. The configuration software can generate load control information (e.g., a load control database) that defines the operation and/or performance of the load control system 100. For example, the load control information may include information about different load control devices of the load control system (e.g., dimmer switch 120, LED driver 130, and/or motorized roller blind 140). The load control information may include information about the association between the load control devices and input devices (e.g., wired keypad device 150, battery-powered remote control device 152, occupancy sensor 154, daylight sensor 156, and/or shadow sensor 158) and/or how the load control devices can respond to inputs received from the input devices.

System controller 110 can be configured to automatically control motorized blinds (e.g., motorized roller blinds 140). Motorized blinds can be controlled to save energy and/or improve the comfort of occupants in buildings where load control system 100 can be installed. For example, system controller 110 can be configured to automatically control motorized roller blinds 140 in response to a clock schedule, a daylight sensor 156, and/or a shadow sensor 158. Roller blinds 140 can be manually controlled by a wired keypad device 150 and/or a battery-powered remote control 152.

Figures 2A and 2C are plan views of a direct current (DC) power distribution system 200 for a control system (e.g., the load control system 100 shown in Figure 1) that can be installed in building 202. The control system may include one or more motorized blinds 240 (e.g., motorized roller blinds 140 shown in Figure 1) for controlling the amount of daylight entering building 202 through respective windows 204. Each motorized blind 240 may include a corresponding roller and a corresponding covering material (not shown), such as the curtain fabric 142 of the motorized roller blind 140 shown in Figure 1. The motorized blind 240 may also include a corresponding motor drive unit 244 (e.g., the motor drive unit 144 shown in Figure 1) configured to adjust the position of the corresponding covering material. Each motor drive unit 244 may include internal energy storage elements, such as one or more rechargeable batteries and/or supercapacitors (e.g., as described in more detail below).

DC power distribution system 200 may include a bus power supply 290 (e.g., a Class 2 power supply) electrically coupled to motor drive unit 244 of motorized curtain 240 via a power bus 292 (e.g., a DC power bus). The bus power supply 290 may be electrically coupled to an AC trunk supply for receiving AC trunk line voltage. The bus power supply 290 may be configured to generate a bus voltage on the bus power supply 292 (e.g., from the AC trunk line voltage) for charging (e.g., trickle charging) the energy storage elements of the motor drive unit 244. The power bus 292 may be daisy-chained electrically coupled to the motor drive unit 244. For example, each motor drive unit 244 may include two power connectors (e.g., a power input connector and a power output connector) to implement each daisy-chain of the motor drive units. The bus power supply 290 may be configured to adjust (e.g., temporarily adjust) the magnitude of the DC bus voltage under certain conditions (e.g., in response to the number of motor drive units 244 currently requiring charging of their internal energy storage elements). Bus power supply 290 may be configured to perform the functions of a system controller (e.g., system controller 110) (e.g., any of the exemplary functions described herein). Furthermore, in some examples, bus power supply 290 may include a system controller (e.g., system controller 110).

As shown in Figure 2A, the power bus 292 may be a single cable (e.g., a single wire segment) that extends around the perimeter of an entire floor of building 202 (e.g., in an approximately complete loop) to charge the energy storage elements of all motor drive units 244 on the floor. The cable of the power bus 292 may include at least two or more wires (e.g., electrical conductors) for distributing the bus voltage from the bus power supply 290 to the motor drive units 244 of the DC distribution system 200. For example, the building may include multiple floors and the DC distribution system 200 may include multiple corresponding power buses 292, with one of the power buses 292 located on each floor of the building. AC trunk power may be coupled to the power bus 292 on each floor of the building via a single circuit breaker 294 on each floor.

The energy storage element of the motor drive unit 244 may have a limited ability to move the covering material of the corresponding motorized curtain 240 (e.g., the ability to power the movement of the covering material). For example, the energy storage element of the motor drive unit 244 may have the ability to power a predetermined number of movements (e.g., complete movements) of the covering material, wherein a complete movement of the covering material may be a movement from a fully raised position (e.g., a fully open position) to a fully lowered position (e.g., a fully closed position) or from a fully lowered position to a fully raised position. The motor drive unit 244 may be configured to limit the number of movements (e.g., complete movements) and/or the total amount of movements (e.g., the number of rotations of the roller) within a certain period of time (e.g., a day) (e.g., to prevent future movements at or after the limit has been exceeded). For example, the motor drive unit 244 may be configured to count the number of movements (e.g., complete movements) during a day and prevent future movements of the covering material after the number of movements (e.g., a predetermined number) exceeds a movement threshold (e.g., less than or equal to ten complete movements, such as approximately five to ten complete movements). Furthermore, the motor drive unit 244 can be configured to store the total amount of movement during a day (e.g., in units of motor rotation and/or linear movement distance of the lower edge of the cover material) and prevent future movement of the cover material after the total amount of movement has exceeded a distance threshold (e.g., a predetermined amount of movement). For example, the distance threshold could be a value representing four complete movements of the cover material between a fully lowered position and a fully raised position. The motor drive unit 244 can also be configured to limit the frequency of movement. The motor drive unit 244 can allow the cover material to move again at the end of the day, at the end of a predetermined period after movement has stopped, and/or when the internal energy storage element has been charged to an acceptable level.

Motor drive units 244 can be configured to communicate with each other via a communication link (not shown) (such as a wired or wireless communication link). For example, if motor drive units 244 are configured to transmit and receive wireless signals (such as radio frequency (RF) signals), power bus 292 can simply include two electrical conductors for supplying voltage and current to the motor drive units. Furthermore, power bus 292 can be encapsulated with a wired digital communication link (e.g., an RS-485 digital communication link) to allow motor drive units 244 to communicate via the wired communication link. Additionally, motor drive units 244 can be configured to communicate with each other by transmitting signals via the two electrical conductors of power bus 292 (e.g., using power line communication (PLC) technology).

Motor drive unit 244 may be configured to know the energy storage level of the energy storage element of other motor drive units 244 in DC power distribution system 200 (e.g., a percentage of the maximum storage capacity of the energy storage element and/or the voltage level of the energy storage element). For example, motor drive unit 244 may periodically transmit the energy storage level of its own energy storage element.

Each motor drive unit 244 can be configured to control when its internal energy storage element is charged. Multiple motor drive units 244 can charge their internal energy storage elements simultaneously. Furthermore, a limited number of motor drive units 244 (e.g., one at a time) can be configured to charge their internal energy storage elements at a time. The motor drive units 244 can be configured to coordinate when each of them charges its internal energy storage element. The motor drive units 244 can be configured to arbitrate with each other via a communication link to determine which(s) should currently be charging its internal energy storage element. The motor drive units 244 can be configured to prioritize which motor drive unit should charge its internal energy storage element based on its power requirements. For example, the motor drive unit 244 with the lowest energy storage level among all motor drive units in the DC power distribution system 200 can be configured to charge its energy storage element before the other motor drive units.

Another device (such as a system controller (e.g., system controller 110) and/or bus power supply 290) may communicate with motor drive units 244 to manage which of one or more motor drive units 244 is currently charging its internal energy storage element (e.g., based on one or more storage levels of one or more internal energy storage elements). The system controller may be configured to know when multiple blackout curtains need to move simultaneously (e.g., as part of a clock schedule, closing all motorized curtains at the end of the day). For example, the system controller may store the movement history of the motorized curtains 240 and may be configured to determine which motor drive unit 244 should charge its internal energy storage element based on the determination of the motorized curtains expected to move next (e.g., the most likely motorized curtain to move). Thus, motor drive units 244 may be configured to control the charging of their internal energy storage elements (e.g., charging the elements to a specific storage level) based on the past and/or expected use of the motorized curtains 240.

Motor drive units 244 can be configured to operate in a normal power mode. In normal power mode, motor drive units 244 can be configured to rotate their motors at normal speeds. Furthermore, in normal power mode, motor drive units 244 can be configured to charge their internal energy storage elements to maximum capacity, or in some examples, to less than maximum capacity, such as 60% of maximum capacity. Motor drive units 244 can be configured to operate in a low power mode during high power demand events and/or during energy depletion events. High power demand events can be periods of high energy usage by multiple load control devices, such as when many (e.g., more than one or most) motorized curtains need to move simultaneously and/or when many (e.g., more than one or most) internal energy storage elements of motor drive units 244 are charging. Energy depletion events can be, for example, when the DC distribution system 200 operates under conditions where many (e.g., most) internal energy storage elements of motor drive units 244 are depleted (e.g., below a threshold storage level such as 20%). When operating in low-power mode, the motor drive unit 244 can be configured to, for example, control the motor to rotate at a slower speed (e.g., to reduce the power consumption of the motor) and/or delay the movement or operation of the motor.

The system controller and/or bus power supply 290 can cause the motor drive unit 244 to enter a low-power mode by transmitting a message to the motor drive unit 244 (e.g., to the control circuitry of the motor drive unit 244). For example, the system controller and/or bus power supply 290 can be configured to transmit a digital message to the motor drive unit 244 (e.g., via RF signal 106) to cause the motor drive unit to enter a low-power mode. Alternatively or additionally, the bus power supply 290 can be configured to detect high-power demand events (e.g., by measuring the magnitude of the output current of the bus power supply) and signal the motor drive unit 244 by generating a pulse on the power bus 292. For example, the bus power supply 290 can generate a pulse by temporarily increasing the magnitude of the DC bus voltage and/or temporarily decreasing the magnitude of the DC bus voltage (e.g., reducing it to approximately zero volts). The motor drive unit 244 can be configured to enter a low-power mode in response to detecting a pulse in the magnitude of the DC bus voltage.

In some cases, one motorized curtain 240 may need to move more frequently than another. If one of the motor drive units 244 determines that its internal energy storage element has a large storage level (e.g., compared to the storage levels of one or more other motor drive units), then the motor drive unit 244 may be configured to share the charge from its internal energy storage element with one or more other motor drive units (e.g., the internal energy storage elements of other motor drive units). Furthermore, multiple motor drive units 244 may be configured to share charge with multiple other motor drive units.

As shown in Figure 2B, the DC power distribution system 200 may further include a supplementary energy storage element 296 (e.g., an external energy storage element) that can be coupled to a power bus 292 between two of the motor drive units 244. The supplementary energy storage element 296 may be configured to charge from the bus power supply 292, for example, when the internal energy storage element of the motor drive unit 244 is charged to a suitable level. For example, during an energy depletion event, the supplementary energy storage element 296 may be configured to charge the internal energy storage element of the motor drive unit 244 located downstream of the supplementary energy storage element 296 on the power bus 292 (e.g., a subset of motor drive units electrically coupled to the power bus 292 after the supplementary energy storage element 296). At this time, the supplementary energy storage element 296 may be configured to disconnect from the bus power supply 290 and the motor drive unit 244 located upstream of the supplementary energy storage element 296 on the power bus 292 (e.g., a subset of motor drive units electrically coupled to the power bus 292 between the supplementary energy storage element 296 and the bus power supply 290). For example, supplementary energy storage elements may include internal switching circuitry, such as relays, for disconnecting from the bus power supply 290. The DC power distribution system 200 may include more than one supplementary energy storage element 296.

The system controller may be configured to determine the existence of an energy depletion event, for example, when the DC power distribution system 200 operates under conditions where most of the internal energy storage elements of the motor drive unit 244 have been depleted. For example, supplemental energy storage element 296 may be configured to log into memory and/or report to the system controller when supplemental energy storage element 296 is needed to charge the internal energy storage elements of the downstream motor drive unit 244. The system controller may be configured to optimize when the motor drive units 244 move and/or charge their internal energy storage elements to avoid further energy depletion events. For example, personal computer 166 may be configured to send an alarm to building managers to indicate that the DC power distribution system 200 is operating under conditions where most of the internal energy storage elements of the motor drive unit 244 have been depleted.

As shown in Figure 2C, the bus power supply 290 may include two output terminals 298a and 298b connected to two power bus branches 292a and 292b extending around the floors of building 202 (e.g., two cables electrically coupled to motor drive units 244). For example, the bus power supply 290 may include a first output terminal 298a electrically coupled to a first subset of motor drive units of a plurality of motorized curtains via a first cable of power bus 292a, and a second output terminal 298b electrically coupled to a second subset of motor drive units of a plurality of motorized curtains via a first cable of power bus 292b. Using the two power bus branches 292a and 292b, the distance between the bus power supply 290 and the motor drive units 244 located at the ends of the power bus branches 292a and 292b can be reduced.

Figure 3 is a block diagram of an exemplary DC power distribution system 300 used in a control system (e.g., the load control system 100 shown in Figure 1). The DC power distribution system 300 may include a bus power supply 310 (e.g., bus power supply 290), one or more motor drive units 330a, 330b, 330c (e.g., motor drive unit 244), and a power bus 340 (e.g., a DC bus voltage). The control system may include one or more motor drive units 330a-330c (e.g., motor drive units of motor blind 140 and/or motor curtain 240). For example, when motor drive units 330a-330c are configured as motor drive units for motor blinds or motor curtains, they may adjust the position of the corresponding covering material to control the amount of daylight entering the building through the corresponding window. The power bus 340 may be daisy-chained electrically coupled to the motor drive units 330 and configured to provide a bus voltage V_{_BUS} to the motor drive units 330a-330c. Although shown as three motor drive units 330a-330c, more or fewer motor drive units may be coupled to the power bus 340.

Each motor drive unit 330a-330c may include corresponding internal load circuits 332a, 332b, 332c, each of which may be a motor or other load within the motor drive unit 330. For example, in some examples, each internal load circuit 332a-332c may include any combination of an internal energy storage element, a motor drive circuit, and a motor. Although described with reference to motor drive unit 330, any control source device and/or control target device may be connected to power bus 340 and configured to operate in a manner similar to motor drive unit 330. The energy storage element of motor drive unit 330 may have a limited ability to move the covering material of a corresponding motorized curtain (e.g., the ability to power the movement of the covering material). For example, the energy storage element of motor drive unit 330 may have the ability to power a predetermined number of movements of the covering material (e.g., complete movements), wherein a complete movement of the covering material may be a movement from a fully lowered position to a fully raised position or from a fully raised position to a fully lowered position. The energy storage element may be any combination of a supercapacitor, a rechargeable battery, and/or other suitable energy storage device. Each motor drive unit 330 can be configured to control when its internal energy storage element is charged. Multiple motor drive units 330 can charge their internal energy storage elements simultaneously.

Each motor drive unit 330a-330c may further include a corresponding current source 334a, 334b, 334c that can be coupled to the power bus 340. For example, the current source 334a of motor drive unit 330a may be coupled between the positive terminal T1a and the negative terminal T2a, the current source 334b of motor drive unit 330b may be coupled between the positive terminal T1b and the negative terminal T2b, and the current source 334c of motor drive unit 330c may be coupled between the positive terminal T1c and the negative terminal T2c. Each motor drive unit 330a-330c may further include a corresponding energy storage element 338a, 338b, 338c (e.g., a capacitor) that can be configured to be charged from the power bus 340 via corresponding diodes 336a, 336b, 336c.

The bus power supply 310 may include a power converter circuit 320, a first controllable switch circuit 322, a second controllable switch circuit 326, and a sensing resistor 324. In some examples, the sensing resistor 324 may be a variable resistor having a resistance R_{_VAR} that can be controlled by the bus power supply 310. The bus power supply 310 may also include control circuitry (not shown), such as a microprocessor, a programmable logic device (PLD), a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or any suitable processing device or control circuitry. The bus power supply 310 may be configured to generate a bus voltage V _{_BUS} on the power bus 340 using the power converter circuit 320. The bus voltage V_{_BUS} may be provided to the power bus 340 when the first controllable switch circuit 322 is turned on and the second controllable switch circuit 326 is turned off. The bus voltage V_{_BUS} may be used to charge (e.g., trickle charge) the energy storage elements 338a-338c of the motor drive units 330a-330c. Furthermore, although not shown in Figure 3, the bus power supply 310 may be electrically coupled to the AC trunk supply for receiving the AC trunk line voltage, and the power converter circuit 320 may be an AC-to-DC converter configured to receive the AC trunk line voltage and generate the bus voltage V _{_BUS} . The control circuitry may determine, for example, the magnitude of the bus voltage V _{_BUS} when the first controllable switch circuit 322 is not turned on and the second controllable switch circuit 326 is turned on. For example, the control circuitry may determine the magnitude of the current conducted through the power bus 340 based on one or more sensing signals. The control circuitry may control the resistance R_{_VAR} of the sensing resistor 324 to adjust the magnitude of the sensing signal received when the control circuitry determines the magnitude of the bus voltage V_{_BUS} (e.g., as will be explained in more detail below).

The power bus 340 can be daisy-chained electrically coupled to the motor drive units 330a-330c. For example, each motor drive unit 330a-330c may include two power connectors (e.g., a power input connector and a power output connector) to implement each daisy link of the motor drive units. Alternatively, each motor drive unit 330a-330c may include a single power connector, and the daisy link (e.g., the connection of the power input and power output wires) may occur at the terminals of the single power connector or outside the single power connector (e.g., using a terminal nut with a third wire terminated at the single power connector). These are just various ways to perform daisy linking. The cable of the power bus 340 may include at least two or more wires (e.g., electrical conductors) for distributing the bus voltage V _BUS from the power converter circuit 320 to the motor drive units 330a-330c of the DC power distribution system 300. The bus power supply 310 can be configured to adjust (e.g., temporarily adjust) the value of the bus voltage V_BUS under certain conditions (e.g., in response to the number of motor drive units 330a-330c that currently need to charge the internal energy storage elements 338a-338c of the motor drive units and/or drive their respective _motors ). The bus power supply 310 can be configured to perform the functions of a system controller (e.g., system controller 110) (e.g., any of the exemplary functions described herein). Furthermore, in some examples, the DC power distribution system 300 may include a system controller (e.g., system controller 110).

The bus power supply 310 may have a power capacity _PCAP (e.g., a limited power capacity) that limits the maximum amount of power that the bus power supply 310 can deliver to the motor drive units 330a-330c via the power bus 340. When one of the motor drive units 330a-330c operates its internal load circuits 332a-332c (e.g., the motor), the motor drive unit may consume most (e.g., all) of the power from the power bus 340 required to operate the internal load circuits. If most (e.g., all) of the motor drive units 330a-330c simultaneously operate their internal load circuits 332a-332c (e.g., and/or need to recharge their respective internal energy storage elements 338a-338c), the cumulative total power required may exceed the power capacity _PCAP of the power converter circuit 320, which in some cases may cause the bus power supply 310 to become overloaded. When the bus power supply 310 becomes overloaded, it may overheat, suffer a shortened product life, and experience a decrease in the value of the bus voltage V _{_BUS}, causing the V_{_BUS} value to drift out of the expected operating range. Even if the bus power supply 310 does not become overloaded, power may be unevenly distributed among the motor drive units 330a-300c. A limitation of the existing system is that a motor drive unit may know how much power it needs, but it may not know how much power all other motor drive units need.

The DC power distribution system 300 may include a system controller (e.g., system controller 110) operating as a master unit. This system controller learns the required power (e.g., demanded power) of each motor drive unit 330a-300c and arbitrates the amount of power that each of the motor drive units 330a-300c may consume at any given time. However, using a system controller to arbitrate power distribution within the system 300 increases overhead, including necessary physical components, increased communication bandwidth, and the necessary computational resources to enable routine communication between the motor drive units 330a-330c and the system controller. For example, if the motor drive units 330a-330c are configured to routinely (e.g., every second) transmit their required power using digital and/or wireless communication technologies, significant bandwidth resources may be required. Therefore, the bus power supply 310 and motor drive units 330a-330c of the DC power distribution system 300 shown in Figure 3 can be configured to use the power bus 340 to enable each of the motor drive units 330a-330c to transmit the required power _PREQ , to know the total required power P _TOT of all motor drive units 330a-330c, to determine the allocated power P _{ALLOC that} the motor drive units 330a-330c may consume at a specific time (e.g., a proportion of the power capacity of the bus power supply 310 (e.g., 100W)), and to consume only the allocated power P _ALLOC from the bus voltage V _BUS across the power bus 340.

Bus power supply 310 can operate the first controllable switching circuit 322 and the second controllable switching circuit 326 in a coordinated manner using a periodic cycle with a periodic time period T _PBUS (e.g., approximately one second). Bus power supply 310 can provide a bus voltage V _BUS on the power bus 340 during the on portion T _ON of the periodic time period T _PBUS . Bus power supply 310 can not provide the bus voltage V _BUS on the power bus 340 during the off portion T _OFF of the periodic time period T _PBUS , for example, to allow motor drive units 330a-330c to each deliver their required power _PREQ to bus power supply 310 and other motor drive units in DC power distribution system 300. Bus power supply 310 can generate the bus voltage V _BUS using power converter circuit 320. The bus power supply 310 can provide a bus voltage V_{_BUS} on the power bus 340 during the on-time T _{_ON} of the periodic period T_PBUS by turning on the controllable switch circuit 322 and turning off the controllable switch circuit 326. When the controllable switch circuit 322 is on and the controllable switch circuit 326 is off and the bus voltage V_{_BUS} is provided on the power bus 340, the motor drive units 330a-330c can charge their internal energy storage elements 338a-338c and/or drive their internal load circuits 332a-332c (e.g., motors) from the bus voltage V_{_BUS}.

Bus power supply 310 may, for example, de-conduct controllable switch circuit 322 and conduct controllable switch circuit 326 during the off portion T _OFF of a periodic time period T _PBUS , for example, to allow motor drive units 330a-330c to each transmit (e.g., transmit the required power _PREQ ) on the power bus 340. For example, bus power supply 310 may periodically de-conduct controllable switch circuit 322 and conduct controllable switch circuit 326 during the periodic time period T _PBUS . For example, the on portion T _ON may be approximately 995 milliseconds and the off portion T _OFF may be approximately 5 milliseconds. It should be understood that even if bus power supply 310 does not provide bus voltage V _BUS on the power bus 340 during the off portion T _OFF , the bus voltage V _BUS may still have a non-zero value during the off portion T _OFF , for example, to allow motor drive units 330a-330c to transmit the required power _PREQ on the power bus 340. Furthermore, even if the bus power supply 310 does not provide the bus voltage V _BUS on the power bus 340 during the off-period T _OFF of each time period, the energy storage elements 338a-338c of each motor drive unit 330a-330c can each operate as a bus capacitor for maintaining the input voltage of the motor drive unit. For example, the bus capacitor can be used to power the corresponding internal load circuits 332a-332c during the off-period T _OFF of each periodic time period T _PBUS .

When controllable switch circuit 322 is not conducting and controllable switch circuit 326 is conducting (e.g., during the off-period T _OFF ), motor drive units 330a-330c (e.g., current sources 334a-334c) can conduct a power demand current I _PR (e.g., a small current) onto power bus 340. The magnitude of the power demand current I _PR may depend on the required (e.g., requested) power _PREQ of motor drive unit 330 (e.g., proportional to it). For example, immediately before or at the start of the off-period T _OFF of the periodic time period T _PBUS , each motor drive unit 330a-330c may estimate its required power based on, for example, the power demand of the corresponding internal load circuits 338a-338c (e.g., whether the motor drive unit is driving its motor, and if so, how much power is needed to drive the motor, etc., and/or whether the corresponding internal energy storage elements 338a-338 need to be recharged). Then, after the start of the off-period T _OFF of the periodic time period T _PBUS , motor drive units 330a-330c can each output their respective power demand currents I _PRa , I _PRb , and I _PRc to the power bus 340, where the value of the power demand current I _PR depends on the required power _PREQ of the motor drive unit (e.g., proportional to it). Motor drive units 330a-330c can each control their respective current sources 334a-334c to conduct their respective power demand currents I _PRa and I _PRc to the power bus 340 during the off-period T _OFF of the periodic time period T _PBUS . The off-period T _OFF of the periodic time period T _PBUS can also be referred to as the communication period.

When the controllable switch circuit 322 is not conducting and the controllable switch circuit 326 is conducting (e.g., during the off-phase T _OFF ), the motor drive units 330a-330c can each detect the magnitude of the bus voltage V _BUS (e.g., which can indicate the magnitude of the power demand currents I _PRa , I _PRb , and I _PRc on the power bus 340) to determine, for example, the total power demand P _TOT of the motor drive units 330a-330c on the power bus. Therefore, each motor drive unit 330a-330c knows its required power _PREQ and the total power demand _PREQ of the motor drive units 330a-330c on the power bus 340. During the next cycle (e.g., the next periodic time T _PBUS ) when the controllable switch circuit 322 is on and the controllable switch circuit 326 is off (e.g., during the next on-phase T _ON ), the motor drive units 330a-330c may each consume their allocated power P _ALLOC from the power bus to charge the corresponding energy storage elements 338a-338c and/or drive their internal load circuits 332a-332c (e.g., motors).

Although described in the context of transmitting the required power _PREQ across the power supply bus, in other examples, motor drive units 330a-330c may transmit other resources as required, such as current, voltage, bandwidth, communication resources, time, etc.

Figure 4A is a block diagram of an exemplary bus power supply 400 (e.g., bus power supply 290 and/or bus power supply 310) used in a DC power distribution system of a load control system (e.g., load control system 100, DC power distribution system 300, etc. shown in Figure 1). The bus power supply 400 (e.g., a type 2 power supply) may be electrically coupled to one or more motor drive units (e.g., motor drive unit 244 and/or motor drive units 330a-330c) via a power bus (e.g., power bus 340). For example, the bus power supply 400 may include one or more power connectors, such as power connector 410 (e.g., including two power terminals, such as a positive terminal and a negative terminal), for receiving input voltage from an external power supply (e.g., an AC trunk line voltage V_{_AC} such as an AC power source). The bus power supply 400 may also include a power connector 412 that can be connected to a power bus electrically coupled to one or more motor drive units in a daisy-chain configuration. Bus power supply 400 can be configured to generate bus voltage _VBUS , and power connector 412 can provide bus voltage _VBUS to the power bus. For example, bus voltage _VBUS may have a Class 2 limit value of less than 60 volts (e.g., approximately 50 volts, such as 48 volts). Motor drive units connected to the power bus can conduct output current _IOUT from bus power supply 400 through power connector 412.

The bus power supply 400 may include a power converter circuit 420, an overpower protection circuit 430 (e.g., an overcurrent protection circuit), and a power bus management circuit 440. The power converter circuit 420 may be coupled to a power connector 410 to receive an input voltage (e.g., an AC trunk line voltage V _{_AC} ) and generate a DC supply voltage V _{_{PS_DC}}. The power converter circuit 420 may be an AC/DC converter or a DC/DC converter, depending on whether the power connector 410 is connected to an AC power source or a DC power source. The DC supply voltage V _{_{PS_DC}} may be a relatively constant voltage. For example, the magnitude of the DC supply voltage V _{_{PS_DC}} may be approximately 50 volts.

Overpower protection circuit 430 can couple the DC supply voltage _{VPS_DC} to the power bus and output a protected supply voltage _{VPS_PRT} (e.g., also having a DC value) under normal operating conditions. Bus power supply 400 can also disconnect power converter circuit 420 from the power bus (e.g., disable bus power supply 400) in response to the output power _POUT of power converter circuit 420 exceeding a threshold (such as the power capacity _PCAP of power converter circuit 420). Overpower protection circuit 430 can determine the output power _POUT of bus power supply 400 by monitoring the current conducted through overpower protection circuit 430 (e.g., the monitored current _IMON ) (e.g., because the protected supply voltage _{VPS_PRT} has a DC value). The monitored current _IMON can be the output current _IOUT plus any current consumed by power bus management circuit 440. The monitored current _IMON can be approximately (e.g., almost) equal to the output current _IOUT . For example, the current consumed by power bus management circuit 440 may be small (e.g., negligible). Furthermore, if the bus power supply 400 does not include the power bus management circuit 440, the monitored current _IMON can be equal to the output current _IOUT . Therefore, the output power _POUT of the power supply 400 can be equal to the output current _IOUT multiplied by the bus voltage _VBUS (e.g., _POUT = _VOUT · _IOUT ).

In the example, the overpower protection circuit 430 may have multiple timing thresholds, each associated with a different power threshold and a different amount of time (e.g., a different amount of time). In some examples, the overpower protection circuit 430 may be configured to disconnect the power converter circuit 420 from the power bus by de-energizing a controllable on/off switch circuit. Furthermore, the overpower protection circuit 430 may be configured to remain disconnected from the power converter circuit 420 from the power bus until, for example, power to the bus power supply 400 is completely removed from the bus power supply 400 and then fully cycled back (e.g., the bus power supply 400 has been turned off and then on again).

The overpower protection circuit 430 of the bus power supply 400 may have a nominal power capacity (e.g., approximately 85 watts, such as 84 watts). For example, the nominal power capacity P _CAP-NOM may be characterized by a nominal power threshold P _TH-NOM , at which point the bus power supply 400 can supply power indefinitely (e.g., when the power converter circuit 420 operates at or below the nominal power threshold P _TH-NOM , the overpower protection circuit 430 may never disconnect the bus power supply 400 from the power bus). For example, the bus power supply 400 may continuously supply power to the power bus at or below the nominal power threshold P _TH-NOM without being interrupted and/or disconnected by the overpower protection circuit 430. The nominal power capacity P _CAP-NOM may correspond to the rated current of the bus power supply 400 (e.g., the rated continuous current of the bus power supply 400). The overpower protection circuit 430 can be configured, for example, to prevent the output power _POUT of the bus power supply 400 from exceeding the nominal power threshold PTH _-NOM indefinitely by disconnecting the power converter circuit 420 from the power bus.

The overpower protection circuit 430 allows the bus power supply 400 to operate (e.g., supply power) at one or more increased power capacities greater than the nominal power capacity P _TH-NOM for up to, but not longer than, a corresponding predetermined increased power period (e.g., based on different corresponding periods of increased power capacity). Allowing the bus power supply 400 to operate at one of the increased power capacities for a corresponding predetermined increased power period allows the bus power supply 400 to cope with peak power consumption on the power bus. For example, devices consuming power from the power bus may all consume power simultaneously or at higher levels when a high power demand event occurs, such as when multiple (e.g., all) motor drive units coupled to the power bus simultaneously drive their motors.

The overpower protection circuit 430 may be configured with a plurality of different power capacities greater than the nominal power capacity, each of which is associated with a different increased power period during which the power converter circuit 420 can supply power at or below the increased power capacity without tripping the overpower protection circuit 430. For example, the overpower protection circuit 430 may be configured with a first increased power capacity characterized by a first increased power threshold P _TH-IP1 (e.g., approximately 150 watts, such as 148 watts) and a first increased power period T _IP1 (e.g., approximately 60 minutes), during which the bus power supply 400 can operate at or below the first increased power threshold P _TH-IP1 (e.g., and above the nominal power threshold P _TH-NOM ) without tripping. If the output power _POUT of the power converter circuit 420 exceeds the nominal power threshold _PTH-NOM (e.g., about 85 watts) and remains below the first increased power threshold PTH _-IP1 (e.g., about 150 watts) for more than the first increased power time period _TIP1 (e.g., about 60 minutes), the overpower protection circuit 430 may trip and disconnect the power converter circuit 420 from the power bus.

The overpower protection circuit 430 may also be configured with a second power increase capacity, characterized by a second power increase threshold _PTH-IP2 (e.g., approximately 240 watts, such as 237 watts) and a second power increase period _TIP2 (e.g., approximately two minutes), during which the bus power supply 400 may operate without tripping at a power increase threshold PTH _-IP2 (e.g., and above the first power increase threshold PTH _-IP1 ). If the output power _POUT of the power converter circuit 420 exceeds the first power increase threshold _PTH-IP1 (e.g., approximately 150 watts) and remains below the second power increase threshold PTH _-IP2 (e.g., approximately 240 watts) for more than the second power increase period _TIP2 (e.g., approximately two minutes), the overpower protection circuit 430 may trip and disconnect the power converter circuit 420 from the power bus. Although described with two power increase capacities, the overpower protection circuit 430 may be configured with more or fewer power increase capacities.

Overpower protection circuit 430 can be configured to momentarily (e.g., near-instantaneously) disconnect power converter circuit 420 from the power bus when the output power _POUT of power converter circuit 420 exceeds the maximum power threshold _PTH-MAX (e.g., when the magnitude of the monitored current _IMON exceeds the maximum current threshold ITH _-MAX ). Overpower protection circuit 430 can use, for example, a third power increase time period _TIP3 (e.g., less than approximately 200 milliseconds) that can be considered near-instantaneously to determine whether the magnitude of output power _POUT exceeds the maximum power threshold PTH _-MAX . For example, the maximum power threshold PTH _-MAX may be equal to the power increase threshold of the highest power increase capacity of overpower protection circuit 430 (e.g., the maximum power threshold PTH _-MAX may be equal to a second power increase threshold PTH _-IP2 ). If the output power exceeds the maximum power threshold PTH _-MAX (e.g., approximately 240 watts) for more than the third power increase period _TIP3 (e.g., less than approximately 200 milliseconds), the overpower protection circuit 430 may trip and disconnect the power converter circuit 420 from the power bus.

In some examples, the overpower protection circuit 430 may rely solely on analog circuitry to disconnect the power converter circuit 420 from the DC power bus (e.g., momentarily disconnecting and/or disconnecting after a certain period of time). The analog circuitry can avoid the need for a microcontroller if the magnitude of the monitored current _IMON exceeds one or more of the increased power thresholds. Avoiding the need for a microcontroller allows the overpower protection circuit 430 to determine that the magnitude of the monitored current _IMON has exceeded one of the increased power thresholds and to disconnect the bus power supply 400 from the DC power supply faster (e.g., momentarily or near momentarily) than could be achieved using a microcontroller (e.g., digital circuitry).

Overpower protection circuit 430 can be configured to determine that the output power _POUT of power converter circuit 420 exceeds one of the increased power capacities for a period of time associated with that increased power capacity. For example, overpower protection circuit 430 can be configured to determine that the magnitude of the monitored current _IMON conducted through overpower protection circuit 430 exceeds a corresponding current threshold associated with each of the increased power capacities for a period of time associated with that increased power capacity. When overpower protection circuit 430 determines that the magnitude of the monitored current _IMON exceeds the corresponding current threshold for a period of time associated with that increased power capacity, overpower protection circuit 430 may disconnect power converter circuit 420 from the power bus (e.g., disable bus power supply 400). In some examples, overpower protection circuit 430 may maintain power converter circuit 420 disconnected from the DC power bus until bus power supply 400 completes a full power cycle by completely removing power from bus power supply 400 and then resuming (e.g., bus power supply 400 has been turned off and then on again).

The overpower protection circuit 430 may include control circuitry, such as a microprocessor, programmable logic device (PLD), microcontroller, application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), or any suitable processing device or control circuitry. In this example, the overpower protection circuit 430 may include a microcontroller and/or analog circuitry configured to perform determination, maintain a voltage signal, disconnect the bus power supply 400 from the DC power bus, operate as a timer, compare signals, and/or any other function within the overpower protection circuit 430.

The power bus management circuit 440 may include a first controllable switch circuit 442 coupled between the output of the overpower protection circuit 430 and the second power connector 412. The power bus management circuit 440 may include a second controllable switch circuit 444 located between the connection point of the first controllable switch circuit 442 and the second power connector 412 and the circuit common terminal through the variable resistor 446, wherein the second controllable switch circuit 444 and the variable resistor 446 are coupled in parallel between the terminals of the second power connector 412.

The power bus management circuit 440 may further include control circuitry 448 for controlling the operation of the power bus management circuitry 440. Control circuitry 448 may include, for example, a microprocessor, a programmable logic device (PLD), a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), and/or any suitable processing device or control circuit. Control circuitry 448 may be configured to generate a first switch control signal _VSW1 for turning the first controllable switch circuit 442 on and off, a second switch control signal _VSW2 for turning the second controllable switch circuit 444 on and off, and a variable resistor control signal VRES _-CNTL for controlling the resistance _RVAR of the variable resistor 446. Control circuitry 448 may control the operation of the first controllable switch circuit 442 and the second controllable switch circuit 444 in a coordinated or mutually exclusive manner. The control circuit 448 can be configured to control the resistance R_{_VAR} of the variable resistor 446 from the minimum resistance R_{_MIN} to the nominal resistance R_NOM (e.g., the maximum resistance), and/or adjust the resistance between the minimum resistance R _{_MIN} and the nominal resistance R _{_NOM} .

Control circuit 448 may receive a first power demand signal, such as a voltage sensing signal V_{_V-SENSE}, which may have a magnitude indicating the bus voltage V_{_BUS} , for example, when the first controllable switch circuit 442 is not turned on and the second controllable switch circuit 444 is turned on (e.g., during the off portion T_{_OFF} of a time period). Control circuit 448 may also receive a second power demand signal, such as a current sensing signal VI _-SENSE , which may have a magnitude indicating the sensed current I_SENSE conducted through the variable resistor 446 (e.g., and the total current I _{_TOTAL} conducted on the power bus), for example, when the first controllable switch circuit 442 is not turned on and the second controllable switch circuit 444 is turned on (e.g., during the off portion T_{_OFF} of a time period).

Control circuit 448 can use the variable resistor control signal VRES _-CNTL to adjust the resistance _RVAR of variable resistor 446 to, for example, adjust the allocated power _PALLOC determined (e.g., estimated) by each motor drive unit on the power bus. Furthermore, for example, when the first controllable switch circuit 442 is not conducting and the second controllable switch circuit 444 is conducting (e.g., during the off portion _TOFF of a time period), adjusting the value of the resistance _RVAR of variable resistor 446 can cause adjustments to the magnitudes of the voltage sensing signal _VV-SENSE and the current sensing signal VI _-SENSE . Additionally, in some examples, control circuit 448 can control the resistance _RVAR of variable resistor 446 to be greater than the resistance on the power bus (e.g., the wires constituting the power bus), but not so great that it delays the time it takes for the wire capacitance to discharge during the off portion _tOFF of each periodic time period _TPBUS . For example, the nominal resistance _RNOM of the variable resistor may be 100 ohms. The bus power supply can be configured to provide a high-side amount of power on the power bus for a limited time (e.g., up to 240 watts for two minutes).

The power bus management circuit 440 may also include a low-voltage power supply 449 that receives a protected supply voltage _{VPS_PRT} and generates a supply voltage _VCC (e.g., approximately 3.3V) to power the control circuit 448 and other low-voltage circuits of the bus power supply 400.

Furthermore, in some examples, the power bus management circuitry 440 may include a current source that can be coupled to the power bus. For example, instead of adjusting the resistance R _{_VAR} of the variable resistor 446, the control circuitry 448 may be configured to conduct current into the variable resistor 446 (e.g., during the off-phase of a periodic time period), for example, to reduce the power allocation P _{_ALLOC} determined by the motor drive unit coupled to the power bus. For example, by conducting current onto the power bus during the off-phase of a periodic time period, the motor drive unit will estimate the amount of current required on the power bus during the larger off-phase period, which will cause them to reduce their proportional allocation during the next on-phase of the periodic time period.

Figure 4B is a block diagram of an exemplary overpower protection circuit 450 (e.g., overpower protection circuit 430) for a bus power supply (e.g., bus power supply 400) used in a DC power distribution system for a load control system. The overpower protection circuit 450 (e.g., an overcurrent protection circuit) can receive the output voltage of a power converter circuit (e.g., the DC supply voltage _{VPS_DC} of the power converter circuit 420 in Figure 4A) and can output a protected supply voltage (e.g., the protected supply voltage _{VPS_PRT} in Figure 4A). The overpower protection circuit 450 may include a power monitoring circuit 452 (e.g., a current monitoring circuit), a controllable switching circuit 454, a latching circuit 458, a drive circuit 471, and multiple threshold comparison and timing circuits, such as first threshold comparison and timing circuits 456a to Nth threshold comparison and timing circuits 456n.

Power monitoring circuit 452 can be configured to monitor the magnitude of the output power _POUT of power converter circuit 420. For example, power monitoring circuit 452 can be configured to monitor the magnitude of the output power _POUT of power converter circuit 420 by monitoring the magnitude of the current flowing through overpower protection circuit 450 (e.g., the monitored current _IMON ). Power monitoring circuit 452 can receive a DC supply voltage _VPS-DC and can measure the magnitude of a sense voltage _VSNS formed in the power monitoring circuit (e.g., across a resistor in the power monitoring circuit) to determine the magnitude of the monitored current _IMON flowing through the resistor. Power monitoring circuit 452 can generate a power monitoring signal, such as a current monitoring signal VI _-MON , which can have a magnitude proportional to the magnitude of the sense voltage _VSNS formed across the resistor in current monitoring circuit 452 and/or the magnitude of the monitored current _IMON . Therefore, the magnitude of current monitoring signal VI _-MON can indicate the magnitude of the monitored current _IMON .

Multiple threshold comparison and timing circuits 456a-465n can be associated with corresponding power levels of the overpower protection circuit 450. These circuits receive a current monitoring signal VI _-MON and output a corresponding signal that can be used to de-energize the controllable switching circuit 454 when the output power _POUT of the power converter circuit exceeds a corresponding increased power threshold for a period of time associated with the corresponding increased power threshold of the overpower protection circuit 450. Since the magnitude of the DC supply voltage _{VPS_DC} (e.g., and the bus voltage _VBUS ) generated by the power converter circuit remains approximately constant, the multiple threshold comparison and timing circuits 456a-465n can determine that the output power POUT of the power converter circuit exceeds the corresponding increased power threshold by determining that the current through the overpower protection circuit 450 (e.g., the magnitude of the monitored current _{IMON )} is greater than the corresponding current threshold for a period of time associated with the corresponding increased power threshold of the overpower protection circuit 450.

Figure 4D illustrates an example of the increased power threshold and associated increased power time period of an overpower protection circuit (e.g., overpower protection circuit 430, overpower protection circuit 450, overpower protection circuit 460, etc.). Multiple threshold comparison and timing circuits 456a-465n can be configured to allow the output power _POUT of the power converter circuit (e.g., as indicated by the magnitude of the monitored current _IMON ) to remain within the nominal power range Range _NOM (e.g., equal to or below the nominal power threshold PTH _-NOM , such as approximately 85 watts) without deactivating the controllable switching circuit 454. Multiple threshold comparison and timing circuits 456a-465n can be configured to allow the output power _POUT of the power converter circuit (e.g., as indicated by the magnitude of the monitored current _IMON ) to remain within a first power range Range ₁ (e.g., above the nominal power threshold PTH _-NOM and equal to or below a first increased power threshold PTH _-IP1 , such as between approximately 84 watts and 150 watts) for a first time period (e.g., a first increased power time period _TIP1 , such as approximately 60 minutes) without deactivating the controllable switching circuit 454. Multiple threshold comparison and timing circuits 456a-465n can be configured to allow the output power _POUT of the power converter circuit (e.g., as indicated by the magnitude of the monitored current _IMON ) to remain within a second power range Range ₂ (e.g., above a first power increase threshold PTH _-IP1 and equal to or below a second power increase threshold PTH _-IP2 , such as between approximately 150 watts and 240 watts) for a second time period (e.g., a second power increase time period _TIP2 , such as approximately 2 minutes) without deactivating the controllable switching circuit 454.

The overpower protection circuit 450 may include a first threshold comparison and timing circuit 456a that can be associated with a first power threshold P _TH1 . For example, the first power threshold P _TH1 may be equal to the nominal power threshold P _TH-NOM . Since the magnitude of the DC supply voltage V _{PS_DC} of the power converter circuit is approximately constant, the first threshold comparison and timing circuit 456a may use a first current threshold I _TH1 (e.g., approximately 1.7 A, such as 1.75 A) corresponding to the first power threshold P _TH1 (e.g., approximately 85 watts, such as 84 watts). The overpower protection circuit 450 may be configured to receive a current monitoring signal _VI-MON and compare the magnitude of the current monitoring signal VI _-MON with a first voltage threshold VI _-TH1 , which may correspond to the first current threshold I _TH1 . Using the current monitoring signal VI _-MON , the first threshold comparison and timing circuit 456a can be configured to determine whether the magnitude of the monitored current _IMON through the overpower protection circuit 450 is greater than the first current threshold _ITH1 for a first power increase period _TIP1 (e.g., approximately 60 minutes). For example, the magnitude of the first voltage threshold VI _-TH1 can be the magnitude corresponding to the magnitude of the first current threshold _ITH1 .

The overpower protection circuit 450 may include a second threshold comparison and timing circuit that can be associated with a second power threshold P _TH2 . For example, the second power threshold P _TH2 may be equal to a first increased power threshold P _TH-IP1 . The second threshold comparison and timing circuit may be characterized by a second current threshold I _TH2 (e.g., which may correspond to the second power threshold P _TH2 , such as approximately 3 amps, such as 3.08 amps) and a second increased power period _TIP2 (e.g., approximately 2 minutes). The second threshold comparison and timing circuit may be configured to determine that the magnitude of the monitored current I _MON through the overpower protection circuit 450 is greater than the second current threshold I _TH2 (e.g., by determining that the magnitude of the current monitoring signal VI _-MON is greater than the second voltage threshold VI _-TH2 ) for the second increased power period _TIP2 .

Furthermore, in some examples, the overpower protection circuit 450 may include a third threshold comparison and timing circuit that can be associated with an instantaneous power threshold. For example, the instantaneous power threshold may be equal to the maximum power threshold P_{_TH-MAX} . The third threshold comparison and timing circuit may be characterized by a third current threshold I _{_TH2} (e.g., which may correspond to the instantaneous power threshold, such as approximately 4.8 amps, or such as 4.94 amps) and a third power increase time period T _{_IP3} (e.g., which may be substantially instantaneous, such as approximately 200 milliseconds). The second threshold comparison and timing circuit may be configured to determine that the magnitude of the monitored current I_{_MON} through the overpower protection circuit 450 is greater than the instantaneous power threshold (e.g., by determining that the magnitude of the current monitoring signal VI _-MON is greater than the maximum voltage threshold VI _-MAX ) for the third power increase time period T _{_IP3} .

If any of the first to Nth comparison and timing circuits determines that the value of the monitored current _IMON is greater than a corresponding threshold for a corresponding time period, the comparison and timing circuit will control a disable signal VI _-DSBL , which can be used to prevent the controllable switching circuit 454 from conducting. Furthermore, although described with reference to three threshold comparison and timing circuits, the overpower protection circuit 450 may include multiple threshold comparison and timing circuits 456a-456n, each of which may be associated with a corresponding nominal or increased power threshold and may be configured with a corresponding current threshold and/or time period.

The latch circuit 458 can receive a disable signal VI _-DSBL , which can be controlled by either the comparison and timing circuits, and in response, the latch circuit 458 generates a latch signal _VLATCH . The drive circuit 471 can be configured to receive the latch signal _VLATCH from the latch circuit 458 and, in response, generate a drive signal _VDR for controlling the controllable switch circuit 454. For example, the drive circuit 471 can de-energize the controllable switch circuit 454 in response to receiving the latch signal _VLATCH , which in turn can disconnect the power converter circuit 420 from the power bus. Therefore, if any of the first to Nth comparison and timing circuits determines that the value of the monitored current _IMON is greater than a corresponding current threshold for a corresponding time period, the controllable switch circuit 454 can be de-energized to disconnect the power converter circuit 420 from the power bus.

When the controllable switch circuit 454 disconnects the power converter circuit 420 from the power bus, the latch circuit 458 can be configured to keep the controllable switch circuit 454 off to maintain the power converter circuit 420 disconnected from the power bus. That is, the latch circuit 458 can maintain the power converter circuit 420 in a disconnected state from the power bus until power to the bus power supply 400 is completely cycled through and then restored (e.g., the bus power supply 400 has been turned off and on again). Alternatively or additionally, the latch circuit 458 can be reset after a timeout period (e.g., turning the controllable switch circuit 454 on) (e.g., without requiring the bus power supply 400 to be turned off and on again).

Figure 4C is a block diagram of an exemplary overpower protection circuit 460 (e.g., overpower protection circuit 430 of Figure 4A and/or overpower protection circuit 450 of Figure 4B) used in a bus power supply (e.g., bus power supply 400) of a load control system's DC power distribution system (e.g., DC power distribution system 300). The overpower protection circuit 460 may include power monitoring circuitry (such as current monitoring circuitry 462 (e.g., current monitoring circuitry 452)), a first threshold comparison and timing circuitry 466a (e.g., first threshold comparison and timing circuitry 456a), a second threshold comparison and timing circuitry 466n (e.g., one of the additional threshold comparison and timing circuitry of the overpower protection circuitry 450), a latching circuitry 468 (e.g., latching circuitry 458), a drive circuitry 473 (e.g., drive circuitry 471), and a controllable switching circuitry 464 (e.g., controllable switching circuitry 454).

The current monitoring circuit 462 may include a resistor 470 (e.g., a sensing resistor) and an amplifier 480. The resistor 470 of the current monitoring circuit 462 may be coupled in series with the controllable switching circuit 464 and may conduct the monitored current _IMON through the overpower protection circuit 460. The current monitoring circuit 462 may be configured to receive a DC supply voltage _{VPS_DC} from a power converter circuit (e.g., power converter circuit 420) of a bus power supply, and the controllable switching circuit 464 may be configured to generate a protected supply voltage _{VPS_PRT} .

The controllable switching circuit 464 may include a pair of field-effect transistors (FETs) Q475a and Q475b (e.g., arranged in an anti-series configuration). The gates of FETs Q475a and Q475b may receive a drive signal _VDR from the drive circuit 472 to turn FETs Q475a and Q475b on and off. The controllable switching circuit 464 may receive the drive signal _VDR and is configured to become off when the drive signal _VDR is low and to become on when the drive signal _VDR is high.

The drive circuit 472 may include an input terminal 473 that can be pulled high to the supply voltage _VCC (e.g., via resistor 414) to turn on FETs Q475a and Q475b. The input terminal 473 of the drive circuit 472 may also be coupled to a circuit common terminal via a series combination of resistor 408 and capacitor 406. For example, when the bus power supply powers on and the low-voltage power supply (e.g., low-voltage power supply 449) begins generating the supply voltage _VCC , the voltage at the input terminal 473 of the drive circuit 472 may begin to rise relative to time. When the magnitude of the voltage at the input terminal 473 exceeds the turn-on voltage of the drive circuit 472 (e.g., approximately 1.6 volts to 2 volts), the drive circuit 472 may turn on FETs Q475a and Q475b. The resistor-capacitor (RC) circuit formed by resistors 408, 414 and capacitor 406 provides a delay between when the bus power supply first receives power and when the controlled switch circuit 464 becomes on (e.g., to allow the bus power supply circuitry to power on before the controlled switch circuit 464 becomes on). FETs Q475a and Q475b can remain on while the magnitude of the voltage at input 473 of the drive circuit 472 remains above approximately the turn-on voltage.

The current monitoring circuit 462 can be configured to monitor (e.g., measure) the magnitude of the monitored current _IMON conducted through the current monitoring circuit 462 and the controllable switching circuit 464. An amplifier 480 of the current monitoring circuit 462 can be configured to receive a sensed voltage _VSNS formed across the resistor 470. The amplifier 480 can output a current monitoring signal VI _{-MON corresponding} to the magnitude of the sensed voltage VSNS. For example, the magnitude of the current monitoring signal VI _-MON can be proportional (e.g., substantially proportional) to the magnitude of the sensed voltage _VSNS , and therefore proportional to the magnitude of the monitored current _IMON .

The first threshold comparison and timing circuit 466a may include a timer 484, a comparator 482, and an AND gate 486. The first threshold comparison and timing circuit 466a may be configured to allow the overpower protection circuit 460 to operate within a first power range (Range ₁ ) (e.g., between approximately 85 watts and 150 watts) for a first time period (e.g., approximately 60 minutes). The comparator 482 may be configured to receive a current monitoring signal VI _-MON (e.g., at the positive input) and a first voltage threshold VI _-TH1 (e.g., at the negative input). The first voltage threshold VI _-TH1 may correspond to a first current threshold _ITH1 (e.g., approximately 1.7 amps) and/or a first power threshold _PTH1 (e.g., approximately 85 watts). In some examples, the first power threshold _PTH1 may correspond to a nominal power threshold PTH _-NOM .

Comparator 482 can be configured to compare the magnitude of the current monitoring signal VI _-MON with a first voltage threshold VI _-TH1 to determine whether the output power _POUT of the power converter circuit is greater than the first power threshold _PTH1 . If the magnitude of the current monitoring signal VI _-MON is lower than the first voltage threshold VI _-TH1 (e.g., the output power _POUT of the power converter circuit is less than or equal to the nominal power threshold PTH _-NOM ), comparator 482 can drive its output low, and if the magnitude of the current monitoring signal VI _-MON is higher than the first voltage threshold _VI-TH1 (e.g., the output power _POUT of the power converter circuit is greater than the nominal power threshold PTH _-NOM ), comparator can drive its output high.

Timer 484 can be configured to start and run for a first time period when the output of comparator 482 is driven high (e.g., when the magnitude of the current monitoring signal VI _-MON is higher than a first voltage threshold VI _-TH1 , indicating that the magnitude of the monitored current _IMON is higher than a first current threshold _ITH1 ). Timer 484 can continue to run as long as the output of comparator 482 is driven high (e.g., as long as the magnitude of the monitored current _IMON is higher than the first current threshold _ITH1 ). While the magnitude of the monitored current _IMON remains higher than the first current threshold _ITH1 , timer 484 can be configured to drive its output low until the first time period expires. If the magnitude of the monitored current _IMON drops below the first current threshold _ITH1 , the output of comparator 482 can be driven low and timer 484 can stop and reset to zero. If the value of the monitored current _IMON remains above the first current threshold _ITH1 while the timer 484 reaches the end of the first time period, the timer 484 can be configured to drive its output high.

The AND gate 486 can receive the outputs of comparator 482 and timer 484. When either the output of comparator 482 or the output of timer 484 is driven low, the AND gate 486 can drive its output low. When both the outputs of comparator 482 and timer 484 are driven high (e.g., indicating that the magnitude of the monitored current I _{_MON} remains above a first current threshold I _{_TH1} for a first time period), the AND gate 486 can drive its output high to control the disable signal VI _-DSBL .

The second threshold comparison and timing circuit 466b may include a timer 490, a comparator 488, and an AND gate 492. The second threshold comparison and timing circuit 466b may be configured to allow the overpower protection circuit 460 to operate for a second time period (e.g., approximately 2 minutes) within a second power range ₂ (e.g., between approximately 150 watts and 240 watts). The comparator 488 may be configured to receive a current monitoring signal VI _-MON (e.g., at the positive input) and a second voltage threshold VI _-TH2 (e.g., at the negative input). The second voltage threshold _VI-TH2 may correspond to a second current threshold _ITH2 (e.g., approximately 3 amps) and/or a second power threshold _PTH2 (e.g., 150 watts).

Comparator 488 can be configured to compare the magnitude of the current monitoring signal VI _-MON with a second voltage threshold VI _-TH2 to determine whether the output power _POUT of the power converter circuit is greater than the second power threshold _PTH2 . If the magnitude of the current monitoring signal VI _-MON is lower than the second voltage threshold VI _-TH2 (e.g., the output power _POUT of the power converter circuit is less than the second power threshold _PTH2 ), comparator 488 can drive its output low, and if the magnitude of the current monitoring signal VI _-MON is higher than the second voltage threshold VI _-TH2 (e.g., the output power _POUT of the power converter circuit is greater than the second power threshold _PTH2 ), comparator can drive its output high.

Timer 490 can be configured to start and run for a second time period when the output of comparator 488 is driven high (e.g., when the magnitude of the current monitoring signal VI _-MON is higher than the second voltage threshold VI _-TH2 , indicating that the magnitude of the monitored current _IMON is higher than the second current threshold _ITH2 ). The second time period may be shorter than the first time period. Timer 490 can continue to run as long as the output of comparator 488 is driven high (e.g., as long as the magnitude of the monitored current _IMON is higher than the second current threshold _ITH2 ). While the magnitude of the monitored current _IMON remains higher than the second current threshold _ITH2 , timer 490 can be configured to drive its output low until timer 490 reaches the end of the second time period. If the magnitude of the monitored current _IMON drops below the second current threshold _ITH2 , the output of comparator 488 can be driven low and timer 490 can stop and reset to zero. If timer 490 reaches the end of the second time period when the value of the monitored current I _MON has remained above the second current threshold I _TH2 , then timer 490 can be configured to drive its output high.

The AND gate 492 can receive the outputs of comparator 488 and timer 490. When either the output of comparator 488 or the output of timer 490 is driven low, the AND gate 492 can drive its output low. When both the outputs of comparator 488 and timer 490 are driven high (e.g., indicating that the magnitude of the monitored current I _{_MON} has remained above the second current threshold I _{_TH2} for a second time period), the AND gate 492 can drive its output high to control the disable signal VI _-DSBL .

Although described using two threshold comparison and timing circuits 466a and 466b, the overpower protection circuit 460 may include any number of threshold comparison and timing circuits (e.g., each with different power thresholds and time periods). For example, the overpower protection circuit 460 may include a threshold comparison and timing circuit 466c configured to output a disable signal VI- _DSBL when the current monitoring signal VI _-MON exceeds a third voltage threshold VI _-TH3 for a third time period (e.g., approximately 200 milliseconds). The third voltage threshold VI _-TH3 may correspond to a third current threshold VI- _TH2 (e.g., approximately 4.8 amps) and/or a maximum power threshold PTH _-MAX (e.g., 240 watts). Therefore, the overpower protection circuit 460 may be configured to momentarily (e.g., nearly momentarily) disconnect from the power bus when the output power _POUT exceeds the maximum power threshold PTH _-MAX .

The effect of the second time period being shorter than the first time period is that, for example, if both the first current threshold _ITH1 and the second current threshold _ITH2 (e.g., or any other threshold) are exceeded for the duration of the second timer, then the second timer 490 will expire before the first timer 484 and trip the overpower protection circuit 460. In other words, if both current thresholds are exceeded simultaneously for the same duration, then the shorter time period (e.g., the one with the higher threshold) will be the time period during which the overpower protection circuit 460 disconnects the power converter circuit from the power bus.

As mentioned above, in some examples, the bus power supply can be configured to adjust (e.g., temporarily adjust) the magnitude of the bus voltage V_{_BUS} under certain conditions (e.g., in response to the number of motor drive units that currently need to charge the internal energy storage elements of the motor drive unit and/or drive their respective motors). If the bus power supply adjusts the magnitude of the bus voltage V _{_BUS}, the bus power supply can adjust the magnitude of the current threshold (e.g., as indicated by the first voltage threshold VI _-TH1 and the second voltage threshold VI _-TH2 ), for example, to keep the power threshold at the same level.

Latch circuit 468 may include comparator 494, resistors 474, 476, 478, 402, 404, and diode 405. Latch circuit 468 may be configured to receive a disable signal VI _-DSBL , which may be coupled to the negative input of comparator 494. Latch circuit 486 may include a first voltage divider including resistors 474, 476 and a second voltage divider including resistors 478, 402. The connection point of resistors 474, 476 in the first voltage divider may be coupled to the negative input of comparator 494, and the connection point of resistors 478, 402 may be coupled to the positive input of comparator 494. Resistors 474, 476, 478, 402 may be sized such that the magnitude of the voltage at the positive input of comparator 494 is greater than the magnitude of the voltage at the negative input of comparator (e.g., unaffected by threshold comparison and timing circuits 466a, 466b). Therefore, when the magnitude of the disable signal _VI-DSBL is low (e.g., if the magnitude of the monitored current _IMON has not exceeded the current threshold for a corresponding time period), comparator 494 can drive its output high. When the disable signal VI _-DSBL is driven high (e.g., if the magnitude of the monitored current _IMON has exceeded the current threshold for a corresponding time period), comparator 494 can drive its output low and thus drive the latch signal _VLATCH low.

Resistor 404 and diode 405 can be connected in series between the positive input and output of comparator 494. When the output of comparator 494 is driven low, the positive input of comparator 494 can be pulled low through resistor 404 and diode 405, preventing the disable signal VI _-DSBL from driving the output of comparator 494 high again. In other words, once the disable signal VI _-DSBL has been driven high, the output of comparator 494 can maintain the latch signal _VLATCH at (e.g., latch it) a low level.

The drive circuit 472 receives the latch signal V _LATCH from the latch circuit 468 via diode 495 and can control the drive signal V _DR based on the latch signal V _LATCH . For example, if the latch signal V _LATCH is high, the drive circuit 472 can control the drive signal V _DR to turn on the controllable switch circuit 464. When the latch signal V _LATCH is driven low, the input terminal 473 of the drive circuit 472 can be pulled low via diode 495 (e.g., below the turn-on voltage of the drive circuit) so that the drive circuit 472 controls the drive signal V _DR to turn off the controllable switch circuit 464. Therefore, if either the threshold comparison and timing circuits 466a, 466b drives the disable signal VI _-DSBL high (e.g., if the value of the monitored current I _MON has exceeded the current threshold for a corresponding time period), the latch circuit 458 can drive the latch signal V _LATCH low, which can cause the drive circuit 472 to turn off the controllable switch circuit 464. For example, the drive circuit 472 can de-conduct FETs Q475a and Q475b to disconnect the power converter circuit from the power bus when the power converter circuit has exceeded the current threshold for a corresponding time period.

Furthermore, the drive circuit 472 may be configured with a maximum current threshold I _{_TH-MAX} to de-energize the controllable switching circuit 464 in response to a large current being conducted through the overpower protection circuit 460. For example, the drive circuit 472 may also receive a current monitoring signal V _{_I-MON} to determine the magnitude of the monitored current I_{_MON}. If the magnitude of the monitored current I _{_MON} exceeds the maximum current threshold I _{_TH-MAX} (e.g., which corresponds to the maximum power threshold P_{_TH-MAX} ), the drive circuit 472 may be configured to cause FETs Q475a and Q475b to disconnect the power converter circuit 420 from the power bus nearly instantaneously (e.g., within less than 200 milliseconds).

Figure 5 shows an example waveform illustrating the operation of a bus power supply (e.g., bus power supply 400) connected to a power bus (e.g., DC power bus) in a DC power distribution system (e.g., DC power distribution system 300). Although described with reference to bus power supply 400, the waveform is applicable to any of the DC power supplies described herein (e.g., bus power supply 290, bus power supply 310, and/or bus power supply 400).

The bus power supply 400 can operate the first controllable switch circuit 442 and the second controllable switch circuit 444 in a coordinated manner to generate a bus voltage V _{_BUS} on the power bus and allow motor drive units to deliver their required power to other motor drive units in the DC power distribution _system . The control circuit 448 can operate the first controllable switch circuit 442 and the second controllable switch circuit 444 periodically (e.g., every second). For example, the control circuit 448 can turn on the first controllable switch circuit 442 and turn off the second controllable switch circuit 444 for the on portion T_{_ON} (e.g., approximately 995 milliseconds) of each of the periodic time periods T _{_PBUS}, and turn off the first controllable switch circuit 442 and turn on the second controllable switch circuit 444 for the off portion T_{_OFF} (e.g., approximately five milliseconds) of each of the periodic time periods T_PBUS. Therefore, the bus power supply 400 can provide the bus voltage V _{_BUS} on the power bus during the on-state T_{_ON} and can stop providing the bus voltage V_{_BUS} on the power bus during the off-state T_{_OFF}. However, it should be understood that the power converter circuit 420 is configured to generate the DC supply voltage V _{_{PS_DC}} regardless of the state of the first controllable switch circuit 442.

Referring to Figure 5, control circuit 448 can deactivate first controllable switch circuit 442 and activate second controllable switch circuit 444 at the start of the off-period T _OFF of each periodic time period T _PBUS (e.g., at time t ₁ ). When first controllable switch circuit 442 is deactivated and second controllable switch circuit 444 is activated, motor drive units can deliver their required power to the power bus. For example, during the off-period T _OFF of each periodic time period T _PBUS , motor drive units can conduct a power demand current I _PR (e.g., a small current) to the power bus. The magnitude of the power demand current I _PR depends on the required power _PREQ of the motor drive unit (e.g., proportional to it). Therefore, during the off-period T _OFF of each periodic time period T _PBUS , the magnitude of the bus voltage V _BUS can depend on the total required power P _TOT of the motor drive units in the DC power distribution system (e.g., proportional to it). Furthermore, control circuit 448 may receive a voltage sensing signal V _{_V-SENSE} indicating the magnitude of the bus voltage V_{_BUS} and/or a current sensing signal VI _-SENSE indicating the magnitude of the sensed current I_{_SENSE} conducted through the variable resistor 446 (e.g., the current conducted through the power bus). Therefore, control circuit 448 can determine the total required power P_{_TOT} of all motor drive units of the DC power distribution system to be used in the next subsequent periodic time T _{_PBUS}.

At time _t2 , which is the end of the off portion T _OFF of the periodic time period T _PBUS (e.g., the beginning of the on portion T _ON ), the control circuit 448 can turn on the first controllable switch circuit 442 and turn off the second controllable switch circuit 444. When the first controllable switch circuit 442 is on and the second controllable switch circuit 444 is off, the power converter circuit 420 can generate a DC supply voltage _{VPS_DC} so that the bus power supply 400 can provide a bus voltage VBUS on the power _bus , and the motor drive units can charge their internal energy storage elements and/or drive their internal load circuits (e.g., motors) through the bus voltage _VBUS . Furthermore, during the on portion T _ON of the periodic time period T _PBUS , the motor drive units can consume their allocated power _PALLOC from the power bus to charge their internal energy storage elements and/or drive their internal load circuits (e.g., motors).

In some examples, the nominal power capacity _PCAP-NOM of the bus power supply 400 and/or the nominal resistance _RNOM (e.g., maximum resistance) of the variable resistor 446 may be known by the bus power supply 400 and/or the motor drive unit. During the off-phase _TOFF , each motor drive unit may control its current source to conduct the corresponding power demand current _IPR onto the power bus, which may cause a change in the bus voltage _VBUS equal to the bus voltage contribution _{VBUS_ONE_DRIVE} on the power bus (e.g., as at least a portion of the magnitude of the bus voltage _VBUS ). For example, the magnitude of the bus voltage contribution _{VBUS_ONE_DRIVE} may be equal to the magnitude of the power demand current _IPR from the current source (e.g., current sources 334a-334c) of the motor drive unit multiplied by the resistance _RVAR of the variable resistor 446. The magnitude of the bus voltage V _{_BUS} during the off-phase T_{_OFF} period can be equal to the sum of the power demand currents I _{_PR} of the current sources of motor drive units 330a-330c multiplied by the resistance R_{_VAR} of the variable resistor 446. Therefore, each motor drive unit can use the magnitude of the power demand current I_{_PR} (e.g., which can be proportional to its required power _PREQ ) and the magnitude of the bus voltage V _{_BUS} (e.g., which can be proportional to the total required power _PREQ-TOT of the motor drive unit) to estimate the proportion K_{_P} of the nominal power capacity P _{_CAP-NOM} of the bus power supply 400 that may be consumed (e.g., K_{_P} = required power / total required power). The allocated power P_{_ALLOC} that each motor drive unit can be allowed (e.g., allocated) to consume from the power bus can be determined as the proportion K_{_P} multiplied by the nominal power capacity P _{_CAP-NOM} of the bus power supply 400.

In some examples, the bus power supply 400 may control the resistance R_{_VAR} of the variable resistor 446 to adjust the estimated allocated power P _{_ALLOC} of each motor drive unit on the power bus. For example, the control circuit 448 may make it appear as if the cumulative total power required (e.g., requested) by all motor drive units for each motor drive unit is greater than (e.g., less than) the actual total power required by all motor drive units. Since each motor drive unit is configured to consume only a proportion of its total required power, the control circuit 448 may adjust the resistance R_{_VAR} of the variable resistor 446 to adjust the magnitude of the cumulative total required power so that the total cumulative required power of all motor drive units appears to have increased (e.g., decreased). Thus, the control circuit 448 may cause each motor drive unit to consume less (e.g., more) power during the next on-state T_{_ON}. For example, if the resistance R_{_VAR} of the variable resistor 446 increases, the total cumulative required power of all motor drive units will appear to need to be greater for the motor drive units, which may cause the allocated power P _{_ALLOC} of each motor drive unit to decrease.

In some examples, it may be desirable for the bus power supply 400 to adjust the power capacity of the bus power supply 400 available to all motor drive units to be higher than the nominal power capacity P _CAP-NOM . Alternatively or additionally, the bus power supply 400 may be configured with one or more additional power capacities, and the bus power supply 400 may be configured to cause the motor drive units to consume less power from the power bus, for example, when the output power P _OUT of the bus power supply 400 exceeds the additional power capacity for a certain period of time (e.g., less than a certain period of time associated with the additional power capacity, such as the time before the bus power supply 400 de-energizes the controllable switching circuit 454).

Figure 6 is a block diagram of an exemplary motor drive unit 500 for an electric blind (e.g., one of the motor drive units 144 of the electric roller blind 140 of Figure 1 and/or one of the motor drive units 244 of the electric blind 240 of Figures 2-2C and/or one of the motor drive units 330 of Figure 3). The motor drive unit 500 may include a motor 510 (e.g., a DC motor) that can be coupled (e.g., mechanically) to raise and lower the covering material. For example, the motor 510 may be coupled to the roller of the electric blind for rotating the roller to raise and lower the covering material (e.g., a flexible material, such as a blackout fabric). The motor drive unit 500 may include load circuitry, such as a motor drive circuitry 520 (e.g., an H-bridge drive circuit), which generates a pulse width modulation (PWM) voltage _VPWM to drive the motor 510 (e.g., to move the covering material between fully lowered and fully raised positions).

Although described using motor 510, motor drive unit 520, and half-effect sensor 540, in some examples, motor drive unit 500 may not include any of these components and may instead be another type of periodic load, such as a high-power sensor including sensing circuitry (e.g., occupancy sensing circuitry with higher power handling, such as radar), periodic light sources such as LED drivers and lighting loads, light sources that consume high power over short periods of time (e.g., ballasts that require more power when lit than during steady-state operation, lighting loads located in infrequently visited locations such as closets, lighting loads on short-time clocks or timers (e.g., external lighting loads triggered by motion, events, or at a predetermined time of day), motorized room dividers, and/or cameras (e.g., configured to detect glare at one or more windows, detect occupants, etc.). Furthermore, although primarily described as a motor drive unit for motorized curtains, motor drive unit 500 can drive any kind of motor for any purpose, such as a motor for a condenser, a burner for a furnace, etc.

The motor drive unit 500 may include control circuitry 530 for controlling the operation of the motor drive unit 500. The control circuitry 530 may include, for example, a microprocessor, a programmable logic device (PLD), a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or any suitable processing device or control circuitry.

Control circuit 530 can be configured to generate a drive signal _VDRV for controlling motor drive circuit 520 to control the rotational speed of motor 510. For example, drive signal _VDRV may include a pulse width modulation signal, and the rotational speed of motor 510 may depend on the duty cycle of the pulse width modulation signal. Furthermore, control circuit 530 can be configured to generate a direction signal _VDIR for controlling motor drive circuit 520 to control the rotational direction of motor 510. Control circuit 530 can be configured to control motor 510 to adjust the current position _PPRES of the blackout fabric of motorized blinds between a fully lowered position _PLOWERED and a fully raised position _PRAISED .

The control circuit 530 may also receive a motor power signal _VPM that indicates the current power consumption of the motor 510. For example, the motor power signal _VPM may have a magnitude indicating the current power consumption of the motor 510. For example, in some examples, the motor drive circuit 520 may filter the drive signal _VDRV , measure the magnitude of the filtered drive signal (e.g., which indicates the average magnitude of the drive signal _VDRV ), and multiply the magnitude of the filtered drive signal by the magnitude of the supply voltage _VSUP to determine the magnitude at which the motor power signal _VPM is generated.

The motor drive unit 500 may include a rotational position sensing circuit, such as a Hall effect sensor (HES) circuit 540, which may be configured to generate two Hall effect sensor (HES) signals _VHES1 and _VHES2 that indicate the rotational position and direction of rotation of the motor 510. The HES circuit 540 may include two internal sensing circuits for generating corresponding HES signals _VHES1 and _VHES2 in response to a magnet that can be attached to the drive shaft of the motor. For example, the magnet may be a circular magnet with alternating north and south pole regions. For instance, the magnet may have two opposite north poles and two opposite south poles, such that each sensing circuit of the HES circuit 540 passes through both north and south poles during a complete rotation of the drive shaft of the motor. Each sensing circuit of the HES circuit 540 may drive the corresponding HES signal _VHES1 , _VHES2 to a high state when the sensing circuit approaches the north pole of the magnet and to a low state when the sensing circuit approaches the south pole. The control circuit 530 can be configured to determine that the motor 510 is rotating in response to the HES signals V _HES1 and V _HES2 generated by the HES circuit 540. Furthermore, the control circuit 530 can be configured to determine the rotational position and direction of the motor 510 in response to the HES signals V _HES1 and V _HES2 .

The motor drive unit 500 may include one or more power connectors, such as two power connectors 550a and 550b (e.g., each including two power terminals, such as a positive terminal and a negative terminal), said one or more power connectors for receiving a bus voltage V_{_BUS} from, for example, an external power supply (e.g., bus power supply 292, bus power supply 310, or bus power supply 400) via a power bus (e.g., power bus 292). For example, one of the two power connectors 550a and 550b may be a power input connector connected to an upstream motor drive unit, and the other of the two power connectors 550a and 550b may be a power output connector connected to a downstream motor drive unit, which allows for simple wiring of the motor drive unit (e.g., in a daisy-chain configuration). The motor drive unit 500 may include a diode D554 configured to receive the bus voltage V _{_BUS} and generate an input voltage V_{_IN} across the bus capacitor C_{_BUS}.

The bus voltage _VBUS can be coupled to the control circuit 530 via a scaling circuit 536, which generates a scaled bus voltage _{VBUS_S} . The control circuit 530 can be configured to determine the magnitude of the bus voltage _VBUS in response to the magnitude of the scaled bus voltage _{VBUS_S} . For example, the control circuit ₅₃₀ can determine the on-state _TON and off-state _TOFF of each periodic time _TPBUS based on the scaled bus voltage VBUS_S. Furthermore, the control circuit can use the scaled bus voltage _{VBUS_S} to determine the total power required (e.g., requested power) of all devices on the power bus during the off-state _TOFF .

The motor drive unit 500 may include a power limiting circuit 552 configured to receive an input voltage V _{_IN} and generate a supply voltage V _{_SUP} . The power limiting circuit 552 may draw an input current I _{_IN} from a power bus and/or bus capacitor C _{_BUS} . The magnitude of the supply voltage V _{_SUP} may be less than the magnitude of the input voltage V _{_IN} . For example, the power limiting circuit 552 may act as a limiter (e.g., a power limiter and/or a current limiter), and in some examples, it may include a power converter circuit used as a limiter. A control circuit 530 may be configured to use a power limiting control signal V _{_PL} to control the operation of the power limiting circuit 552 to control (e.g., increase or decrease) the magnitude of the input current I_{_IN} and/or the magnitude of the supply voltage V _{_SUP}. The supply voltage V _{_SUP} may be coupled to the control circuit 530 via a scaling circuit 532 that generates a scaled supply voltage V _{_SUP_S} . The control circuit 530 may be configured to determine the magnitude of the supply voltage V_SUP in response to the magnitude of the scaled supply voltage V_{_SUP_S} .

The motor drive unit 500 may include a charging circuit 553 (e.g., receiving a supply voltage V _{_SUP} ) and an energy storage element 555. The energy storage element 555 may include one or more supercapacitors, rechargeable batteries, or other suitable energy storage devices. The supercapacitor of the motor drive unit may have an energy storage capacity in the range of approximately 12-26 J/cm^³. In contrast, an electrolytic capacitor may have an energy storage capacity of approximately 1 J/cm^³ (e.g., in the range of approximately 1/10 to 1/30 of a supercapacitor), while a battery may have an energy storage capacity greater than approximately 500 J/cm^³ (e.g., approximately 15 to 50 times (or more) the energy storage capacity of a supercapacitor).

Charging circuit 553 can be configured to charge energy storage element 555 with supply voltage _VSUP to generate storage voltage _VES across energy storage element 555. Charging circuit 553 can also be configured to draw current from energy storage element 555 to use storage voltage _VES to generate (e.g., supplement) supply voltage _VSUP . Storage voltage _VES can be coupled to control circuit 530 via scaling circuit 534, which generates scaled storage voltage _{VES_S} . Control circuit 530 can be configured to determine the magnitude of storage voltage _VES in response to the magnitude of scaled storage voltage _{VES_S} .

The motor drive unit 500 may include a current source circuit 570, which may be coupled across power connectors 550a, 550b. Control circuitry 530 may be configured to use a current source control signal _VCS to control the operation of the current source circuit 570 to control (e.g., during the off-period _TOFF of each periodic time _TPBUS ) the magnitude of the power demand current _IPR (e.g., source current) conducted to the power bus, wherein the magnitude of the power demand current _IPR depends on (e.g., is proportional to) the power required by the motor drive unit 500. The control circuit 530 may estimate the magnitude of the power demand current IPR to be conducted to the power bus based on any combination of the current power consumption P _MOT of the motor 510 (e.g., using the magnitude of the motor power signal V _PM ), the magnitude of the voltage decay of the charge of the energy storage element 555 (e.g., by determining the difference between the magnitude of the storage voltage V _ES and the maximum storage voltage V _{ES_MAX} of the energy storage element 555), and/or the standby power consumption P _STANDBY of the motor drive unit 500 (e.g., the power consumption of circuitry other than the motor 510 ₎ .

In some examples, control circuitry 530 may estimate the magnitude of the power demand current _IPR to be conducted onto the power bus based on (e.g., further based on) one or more scaling factors (e.g., scaling factors K _{_IPR} , K_{_PM}, and K _{_ES}). For example, control circuitry 530 may use the current power dissipation P_{_MOT} of motor 510, the magnitude of the stored voltage V _{_ES}, the maximum stored voltage V _{_ES_MAX} , and scaling factors K_{_IPR}, K _{_PM} , and K _{_ES} to estimate the magnitude of the power demand current _IPR , for example,

The scaling factor K_{_IPR} can be based on the resistance of the sensing resistor in the bus power supply (e.g., the nominal resistance R _{_NOM} of the variable resistor 426) and the maximum possible bus voltage V_{_BUS} on the power bus during the off-period T_{_OFF} of each periodic time T_{_PBUS} (e.g., half the average bus voltage V_{_BUS} ). K _{_PM} can be based on the power usage requirements of motor 510, and the scaling factor K_{_ES} can be based on the energy storage element (e.g., the magnitude of the stored voltage V_{_ES} across the energy storage element). In some examples, the scaling factor K _{_IPR} can be equal to one, and the scaling factor K_{_PM} can be equal to 1/5000. The scaling factor K _{_ES} can be the maximum amount of power that the motor drive unit can request when its energy storage element is empty (e.g., the stored voltage V _{_ES} = 0V). The value of K_{_ES} * V _{_ES_MAX}</sub> can be selected such that it is much smaller than K_{_PM} * V_{_PM}. In some examples, the scaling factor K_{_IPR} can be equal to the total power demand current I_{_PR} from all devices divided by the total power required during the off-period T_{_OFF}. It should be understood that in some examples, the scaling factor may be omitted.

Control circuit 530 can estimate the allocated power _{P_ALLOC} that power limiting circuit 552 can (e.g., during _{the ON} phase T_ON) consume from the power bus and/or bus capacitor _{C_BUS} to charge energy storage element 555 and/or drive motor 510. Control circuit 530 can estimate the proportional amount _{K_P} that the motor drive unit 500 is allowed (e.g., allocated) to consume from the power bus, based on the nominal power capacity _{P_CAP-NOM} of the bus power supply (e.g., bus power supply 400). For example, the proportional amount _{K_P} can be equal to the required power _{P_REQ} of motor drive unit 500 divided by the total required power _{P_TOT} of motor drive units (e.g., all motor drive units) on the power bus.

_KP = _PREQ / _PTOT . Equation 2

Control circuit 530 can be configured to estimate the allocated power _PALLOC by multiplying the nominal power capacity PCAP _-NOM by a proportionality _KP , for example,

P _ALLOC ＝K _P P _CAP-NOM 。 Equation 3

Control circuit 530 can control power limiting circuit 552 based on allocated power P _ALLOC , such that motor drive unit 500 consumes a proportion K _P of nominal power capacity P _CAP-NOM from the power bus during the on-state T _ON of each periodic time T _PBUS . Furthermore, and for example, motor drive unit 500 can consume allocated power P _ALLOC from bus capacitor C _BUS during the off-state T _OFF of each periodic time T _PBUS .

The motor drive unit 500 may also include a power supply 558 that receives a supply voltage _VSUP and generates a low-voltage supply voltage _VCC (e.g., approximately 3.3V) to power the control circuit 530 and other low-voltage circuits of the motor drive unit 500. The power supply 558 may, for example, conduct current from the energy storage element 555 and/or the power limiting circuit 552 when the control circuit 530 controls the motor drive circuit 520 to rotate the motor 510.

In some examples, the charging circuit 553 is configured to conduct an average current from the power bus that satisfies (or exceeds) the peak current required by the motor drive circuit 520 to drive the motor 510. However, in other examples, the charging circuit 553 is configured to conduct an average current from the power bus that is much smaller than the peak current required by the motor drive circuit 520 to drive the motor 510. The storage level of the energy storage element 555 may decrease as the motor 510 rotates and may slowly increase as the charging circuit 553 charges the energy storage element (e.g., trickle charging). For example, the energy storage element 555 of the motor drive unit 500 may have the capability to power a predetermined number of complete movements of the covering material (e.g., less than or equal to 10 complete movements, such as approximately 5-10 complete movements).

The motor drive unit 500 may include a communication circuit 542 that allows the control circuit 530 to transmit and receive communication signals, such as wired communication signals and/or wireless communication signals (such as radio frequency (RF) signals). For example, the motor drive unit 500 may be configured to transmit signals to an external control device (e.g., the motor drive unit 244 shown in Figures 2A to 2C).

The motor drive unit 500 may also include a user interface 544 with one or more buttons that allow the user to provide input to the control circuitry 530 during the setting and configuration of the motorized blinds. The control circuitry 530 may be configured to control the motor 510 in response to a blind movement command received from a communication signal received via communication circuitry 542 or from user input via the buttons on the user interface 544. The user interface 544 may also include a visual display, such as one or more light-emitting diodes (LEDs), which may be illuminated by the control circuitry 530 to provide feedback to the user of the motorized blind system. The motor drive unit 500 may include a memory (not shown) configured to store the current position P _PRES and/or limits (e.g., fully raised position P _RAISED and fully lowered position P _LOWERED ) of the blackout fabric. The memory may be implemented as an external integrated circuit (IC) or internal circuitry of the control circuitry 530.

In some examples (e.g., alternative examples), control circuitry 530 may be configured to periodically transmit messages including the storage level (e.g., the magnitude of the storage voltage V _{_ES} ) of energy storage element 555 via communication circuitry 542. Control circuitry 530 may be configured to learn, via messages received through communication circuitry 542, the storage levels of energy storage elements of other motor drive units coupled to the power bus in the DC power distribution system. Control circuitry 530 may be configured to communicate with other motor drive units to coordinate when each of the charging circuits 553 charges its energy storage element 555. Control circuitry 530 may generate a charging enable signal V _{_CHRG} for enabling and disabling charging circuitry 553 (e.g., to charge energy storage element 555 based on communication with other motor drive units).

The motor drive unit 500 may also include a controllable switching circuit 560 coupled between the energy storage element 555 and power connectors 550a, 550b via a diode D562. A control circuit 530 may generate a switching control signal _VSW to turn the controllable switching circuit 560 on and off. The control circuit 530 may be configured to turn on the controllable switching circuit 560 to bypass one or more components of the motor drive unit 500 (e.g., charging circuit 553 and diode D554) and allow the energy storage element 555 to charge energy storage elements of other motor drive units coupled to the power bus. Control circuit 530 may allow energy storage element 555 to charge the energy storage element of other motor drive units coupled to the power bus based on the storage level of the energy storage element of other motor drive units (e.g., if the storage level of the energy storage element of other motor drive units is low), based on messages received from the system controller, based on messages received from another motor drive unit, based on the determination that another motor drive unit is charging from the power bus, based on the determination that another motor drive unit is in use/moving the motor, based on the determination that another motor drive unit has an upcoming energy usage event, and/or based on the determination that another motor drive unit has a high power demand event.

Furthermore, in some examples, the motor drive unit 500 may include a boost converter (not shown) connected in series with or replacing the switch 560. In such examples, the control circuitry 530 may be configured to increase (e.g., boost) the voltage across the energy storage element 555 when the energy storage element 555 is connected to a power bus (e.g., when power from the energy storage element 555 is supplied to the power bus). For example, including a boost converter in the motor drive unit 500 may be advantageous when the internal storage element 555 has a low rated voltage.

DC power distribution systems (e.g., load control system 100 and/or DC power distribution system 300 shown in Figure 1) may include various types of control devices, such as various input devices. For example, as described above, a DC power distribution system may include one or more wired keypad devices, one or more battery-powered remote control devices, one or more occupancy sensors, one or more daylight sensors, one or more shadow sensors, one or more radar sensors, and/or one or more cameras (e.g., configured to detect glare at one or more windows, detect occupants, etc.).

Figure 7 illustrates an example of a control device 600 (e.g., an input device such as a wired keypad device 150, a battery-powered remote control device 152, an occupancy sensor 154, a daylight sensor 156, and/or a shadow sensor 158) used in a DC power distribution system (e.g., the load control system 100 shown in Figure 1). The control device 600 may include a load circuit 610. For example, the load circuit 610 may include sensors and/or sensing circuitry (e.g., when the control device 600 is an occupancy sensor, a daylight sensor, and/or a shadow sensor) and/or light sources, such as one or more LEDs (e.g., when the control device 600 is a keypad, a battery-powered remote control, or a low-power light source). However, in some examples, such as when the control device 600 is, for example, a wireless adapter circuit, the control device 600 may not include a load circuit 610 because the control device 600 already includes a communication circuit 642.

The control device 600 may include control circuitry 630 for controlling the operation of the control device 600. Control circuitry 630 may include, for example, a microprocessor, a programmable logic device (PLD), a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or any suitable processing device or control circuitry. Control circuitry 630 may be configured to generate a control signal _VCNTL for controlling the load circuit 610 to control an internal load, for example, in an example where the control device 600 includes a load circuit.

Control device 600 may include communication circuitry 642, which allows control circuitry 630 to transmit and receive communication signals, such as wired and/or wireless communication signals (e.g., radio frequency (RF) signals). For example, control device 600 may be configured to transmit signals to an external control device (e.g., any control target device in load control system 100). Control device 600 may also include a user interface 644 with one or more buttons that allow the user to provide input to control circuitry 630, for example, to control one or more control target devices. User interface 644 may also include a visual display, such as one or more light-emitting diodes (LEDs), which may be illuminated by control circuitry 630 to provide feedback to the user of control device 600. Alternatively, the visual display (e.g., one or more LEDs) may be part of load circuitry 610. Control device 600 may include a memory (not shown) configured to store one or more operating settings of control device 600. The memory may be implemented as an external integrated circuit (IC) or as internal circuitry of control circuitry 630.

The control device 600 may include one or more power connectors, such as two power connectors 650a and 650b (e.g., each including two power terminals, such as a positive terminal and a negative terminal), said one or more power connectors for receiving a bus voltage V_{_BUS} from, for example, an external power supply (e.g., bus power supply 292, bus power supply 310, or bus power supply 400) via a power bus (e.g., power bus 292). For example, one of the two power connectors 650a and 650b may be a power input connector connected to an upstream motor drive unit, and the other of the two power connectors 650a and 650b may be a power output connector connected to a downstream motor drive unit, which allows for simple wiring (e.g., daisy-chain configuration) of the motor drive unit and other devices to the power bus.

The control unit 600 can be configured to (e.g., using the bus voltage V _{_BUS} ) draw a relatively constant current from the power bus. That is, the control unit 600 can consume a relatively constant and continuous amount of power from the power bus. This contrasts with a motor drive unit coupled to the power bus, which operates relatively infrequently (e.g., a few times a day) but requires a large amount of power during its operation.

Control device 600 may include a current source circuit 670 coupled across power connectors 650a, 650b. In some examples, control circuit 630 may be configured to use a current source control signal V _CSC to control the operation of current source circuit 670 to control (e.g., during the off-period T _OFF of each periodic time T _PBUS ) the magnitude of the power demand current I _PR (e.g., source current) conducted to the power bus, wherein the magnitude of the power demand current I _PR conducted to the power bus depends on (e.g., is proportional to) the power demand _PREQ of control device 600. In some examples, for example, when control device 600 draws a constant current from the power bus (e.g., when the magnitude of the input current V _IN is relatively constant over time), control circuit 630 may control the magnitude of the power demand current I _PR to be the same for each periodic time T _PBUS off-period T _OFF . However, in some examples, the current source circuit 670 is not controlled by the current source control signal V _CSC , but is configured (e.g., pre-configured) to conduct a constant power demand current I _PR (e.g., with a magnitude of approximately 3 mA) during the off-phase T _OFF of each periodic time period T _PBUS .

Finally, in some examples, control device 600 may not include current source circuit 670, and control device 600 may consume a constant amount of power from the power bus and not use the power demand current _IPR to transfer this power to other devices on the power bus. In such examples, a bus power supply (e.g., bus power supply 400) connected to the power bus may determine, for example, by averaging the steady-state load on the power bus to determine the constant amount of power required by one or more control devices 600 connected to the power bus. Therefore, the bus power supply may then control the resistance _RVAR of a variable resistor during the off-state portion _TOFF of each periodic time period _TPBUS to ensure that one or more constant power loads are continuously supplied with sufficient power on the power bus (e.g., regardless of the power requirements of any peak loads coupled to the power bus, such as one or more motor drive units).

The bus voltage V _{_BUS} can be coupled to control circuitry 630 via scaling circuitry 636, which generates a scaled bus voltage V _{_{BUS_S}} . Control circuitry 630 can be configured to determine the magnitude of bus voltage V_{_BUS} in response to the magnitude of scaled bus voltage V _{_{BUS_S}} . Furthermore, using scaled bus voltage V _{_{BUS_S}} , control circuitry 630 can be configured to determine the power requests of all other devices on the DC power bus and/or determine when the bus power supply on the DC power bus starts and stops generating bus voltage V _{_BUS} (e.g., to determine the on and off portions T_{_ON} and T_{_OFF} of each periodic time period T _{_PBUS} ).

The control device 600 may also include a power supply 652 that receives an input voltage _VIN and generates a supply voltage _VCC (e.g., approximately 3.3V) to power the control circuit 630 and other low-voltage circuitry of the control device 600. The control circuit 630 may receive a power supply control signal _{VPS_CNTL} indicating the power being used by the power supply 652. The supply voltage _VCC may be coupled to the control circuit 630 via a scaling circuit 632 that generates a scaled supply voltage _{VCC_S} . The control circuit 630 may be configured to determine the magnitude of the supply voltage _VCC in response to the magnitude of the scaled supply voltage _{VCC_S} . In some examples, the power supply 652 may be controlled by the control circuit 630 (e.g., via a power limit control signal _VPL ) to limit the supply voltage _VCC . For example, the control circuit 630 may be configured to use the power limit control signal _VPL to control the operation of the power supply 652 to control the magnitude of the supply voltage _VCC .

Figure 8 illustrates an example of waveforms showing the operation of two motor drive units (e.g., motor drive unit 500) connected to a power bus (e.g., DC power bus) of a DC power distribution system (e.g., DC power distribution system 300). In Figure 8, a first motor drive unit (MDU "A") operates its motor first, and a second motor drive unit (MDU "B") operates its motor second. The first and second motor drive units may be coupled to the same DC power bus (e.g., power buses 292, 340) and supplied with the bus voltage V_{_BUS} from the same bus power supply (e.g., bus power supplies 310, 400).

As described above, the bus power supply can periodically (e.g., every second) operate the first and second controllable switching circuits (e.g., the first controllable switching circuit 442 and the second controllable switching circuit 444). For example, as mentioned above, the bus power supply can turn on the first controllable switching circuit and turn off the second controllable switching circuit for the on portion T_{_ON} of each time period T _{_PBUS} (e.g., 995 milliseconds), and turn off the first controllable switching circuit and turn on the second controllable switching circuit for the off portion T_{_OFF} of each time period T_{_PBUS} (e.g., five milliseconds). Therefore, the bus power supply can provide the bus voltage V_{_BUS} on the power bus during the on portion T_{_ON} and can stop providing the bus voltage V_{_BUS} on the power bus during the off portion T_{_OFF}.

Before time _t1 , the respective motors of the first and second motor drive units can be stopped, and the stored voltages V _{_ES(A)} and V_{_ES(B)} across the respective energy storage elements (e.g., energy storage device 555) can be in steady-state conditions (e.g., at a constant maximum capacity V_{_ES_MAX} ). Furthermore, before time _t1 , the input current I _{_IN(A)} at the first motor drive unit and the input current I _{_IN(B)} at the second motor drive unit can be in steady-state conditions. For example, the supply voltages V _{_SUP(A)} and V _{_SUP(B)} can be at relatively small constant values. At time _t1 , the first motor drive unit can, for example, control the drive signal V _{_DRV} to drive its motor (e.g., motor 310) in response to receiving a user input or control signal indicating a new position of the covering material of the motorized curtain. The first motor drive unit can consume power from the energy storage device to drive the motor, and therefore, the stored voltage V _{_ES(A)} across the energy storage elements can begin to decrease from time _t1 . In addition, the motor power signal VPM _(A) of the first motor drive unit can indicate the power that the motor is using.

At time _t2 , the bus power supply can de-energize the first controllable switching circuit and energize the second controllable switching circuit to stop generating the bus voltage V _{_BUS} across the power bus. Time _t2 may represent the start of the off-time portion T_{_OFF} of the time period T _{_PBUS}. In some examples, the first motor drive unit and/or the second motor drive unit may be configured to determine the occurrence of the off-time portion of the periodic time period T_{_PBUS} when the magnitude of the bus voltage V_{_BUS} drops below a threshold. At time _t2 (e.g., or immediately before time _t2 ), the first and second motor drive units may estimate their required power from the power bus. Then, at time _t2 (e.g., or immediately after time _t2 ), the first and second motor drive units may supply the power demand current I_{_PR} to the power bus based on the magnitude of the power demand of the respective motor drive unit (e.g., proportional to it). For example, the first motor drive unit may use the current source control signal V _CSC to control the operation of the current source circuit (e.g., current source circuit 570) to control the magnitude of the power demand current I _{PR (A)} conducted to the power bus, wherein the magnitude of the power demand current I _{PR (A)} depends on (e.g., is proportional to) the power required by the first motor drive unit.

As mentioned above, the first motor drive unit may estimate the magnitude of the power demand current IPR(A) based on the power the motor is using (e.g., using the motor power signal VPM _(A) ), the decay level of the charge of the energy storage element 555 (e.g., by comparing the magnitude of the storage voltage _VES with the maximum storage voltage _{VES_MAX} of the energy storage element ₅₅₅ ), and one or more scaling factors in some examples. Since the second motor drive unit is not driving its motor at time _t2 , and the energy storage element of the second motor drive unit is above a threshold voltage level (such as _{VES_MAX} ), the second motor drive unit may not control the magnitude of the power demand current _IPR ( _B ) to be conducted to the power bus (e.g., control the magnitude of the power demand current _IPR(B) to zero).

At a time delay _TDELAY after the start of the off portion _TOFF of time period _TPBUS (e.g., after time _t2 ), the first motor drive unit and the second motor drive unit may, for example, use a scaled bus voltage _{VBUS_S} to measure the total voltage across the power bus. For example, the first motor drive unit may measure the total voltage across the power bus at time _t10 . Based on the desired power of the first motor control unit and the total required power of all motor drive units, the first motor drive unit may estimate the amount of power it can consume during the next on portion _TON (e.g., a proportional power). For example, the first motor drive unit may estimate the allocated power as a proportional fraction of its desired power (e.g., based on the power demand current _IPR(A) ) divided by the total required power of all devices on the power bus (e.g., based on the bus voltage _VBUS ). During the off-time _TOFF period between time _t2 and time _t3 , the value of the bus voltage _VBUS can be equal to the resistance _RVAR of the variable resistor of the bus power supply multiplied by the value of the power demand current _IPR(A) (e.g., _VBUS = _RVAR · _IPR(A) ).

At time _t3 , the bus power supply can turn on the first controllable switch circuit and turn off the second controllable switch circuit to provide the bus voltage _VBUS during the on-state portion _TON (e.g., 995 milliseconds) of the next periodic time period _TPBUS . Time _t3 may correspond to the end of the off-state portion _TOFF of the previous periodic time period _TPBUS and the beginning of the on-state portion TON of the next periodic time period _TPERIOD . Furthermore, at time _t3 , the first and second motor drive units can begin consuming the allocated power amount (e.g., proportional power amount) from the DC power bus based on an estimated power allocation from the DC power bus during the on-state portion TON of the current period _TPERIOD (e.g., which the first motor drive unit is entitled to). For example, the first motor drive unit can control the operation of a power limiting circuit (e.g., power limiting circuit 552) based on the estimated power allocation from the DC power bus during the _{on-state portion} TON of the current period TPERIOD. The first motor drive unit can consume allocated power _PALLOC from the power bus during the on-time _TON portion of the current time period _TPBUS to drive the motor and recharge the internal energy storage element of the first motor drive unit. Therefore, the input current _IIN(A) of the first motor drive unit can begin to increase at time _t3 , and the energy storage element can begin to recharge. For example, the power limiting circuit of the first motor drive unit (e.g., power limiting circuit 552) can control the increase of the input current _IIN(A) at time _t3 (e.g., gradually). Since the bus voltage _VBUS is substantially constant, the input power is proportional to the input current _IIN(A) (e.g., as shown in Figure 8).

Furthermore, since the second motor drive unit does not request any power from the DC power bus during the off-phase T _OFF of the previous time period T _PBUS (e.g., the second motor drive unit does not generate a power demand current I _PR(B) during the off-phase T _OFF ), the second motor drive unit may not consume any power (e.g., additional power) from the DC power bus during the on-phase T _ON of the current time period T _PBUS . Therefore, the input current I _IN(B) of the second motor drive unit does not increase during the on-phase T _ON of the current time period T _PBUS .

At time _t4 , the second motor drive unit may, for example, generate a drive signal _VDRV to drive its motor in response to receiving a user input or control signal indicating a new position of the covering material of the motorized curtain. The second motor drive unit may consume power from the energy storage device to drive the motor, and therefore, the stored voltage VES _(B) across the energy storage element may begin to decrease from time _t4 . Furthermore, the motor power signal VPM _(B) of the second motor drive unit may indicate the power being used by the motor.

At time _t5 , the bus power supply can deactivate the first controllable switching circuit and activate the second controllable switching circuit to stop the generation of the bus voltage V _{_BUS} across the DC power bus. Time _t5 can represent the start of the off-state portion T_{_OFF} of the time period T _{_PBUS} . At time _t5 (e.g., or immediately before time _t5 ), the first and second motor drive units can estimate their required power from the DC power bus. Then, at time _t5 (e.g., or immediately after time _t5 ), the first and second motor drive units can supply a power demand current I_{_PR} to the DC power bus based on the magnitude of the power demand current I_PR(A) conducted to the DC power bus, depending on (e.g., proportional to) the required power of the respective motor drive unit. For example, the first motor drive unit can control the operation of the current source circuit to control the magnitude of the power demand current I _{_PR(A)} conducted to the DC power bus, wherein the magnitude of the power demand current I _{_PR(A)} depends on (e.g., proportional to) the required power of the first motor drive unit. Similarly, the second motor drive unit can control the operation of the current source circuit to control the magnitude of the power demand current _IPR(B) conducted to the DC power bus, wherein the magnitude of the power demand current _IPR(B) depends on (e.g., is proportional to) the required power of the second motor drive unit. Since both the first and second motor drive units provide (e.g., conduct) the corresponding power demand currents _IPR(A) and _IPR(B) to the DC power bus, the magnitude of the bus voltage _VBUS during the off-state portion _TOFF between times _t5 and _t6 can be greater than (e.g., twice the magnitude) the bus voltage _VBUS during the off-state portion _TOFF between times _t2 and _t3 . For example, during the off-time _TOFF between time _t5 and time _t6 , the bus voltage _VBUS can be equal to the resistance _RVAR of the variable resistor of the bus power supply multiplied by the combination of the power demand currents _IPR(A) and _IPR(B) (e.g., _VBUS = _RVAR · ( _IPR(A) + _IPR(B) )).

At time _t11 (e.g., after a time delay _TDELAY following the start of the off portion _TOFF of the time period _TPBUS from time _t5 ), the first motor drive unit and the second motor drive unit can measure the magnitude of the bus voltage _VBUS across the DC power bus (e.g., using a scaled bus voltage _{VBUS_S} ). For example, the first motor drive unit and the second motor drive unit can measure the magnitude of the bus voltage _VBUS across the DC power bus at time _t11 . Based on the desired power amount of the motor control unit and the total power required by all motor drive units, the first motor drive unit and the second motor drive unit can estimate the allocated power amount (e.g., proportional power amount) that they can consume during the next time period _TPBUS . For example, the first motor drive unit and the second motor drive unit can estimate the amount of power to be allocated as a percentage of their expected power (e.g., based on the power demand current IPR _(A) of the first motor drive unit and the power demand current _IPR(B) of the second motor drive unit) divided by the total power required by all devices on the DC power bus (e.g., based on the bus voltage _VBUS during the off-phase _TOFF ).

At time _t6 , the bus power supply can turn on the first controllable switching circuit and turn off the second controllable switching circuit to provide the bus voltage _VBUS for the on-state portion _TON (e.g., 995 milliseconds) of the next time period _TPBUS . At time _t6 , the first motor drive unit and the second motor drive unit can begin to consume the allocated (e.g., proportional) amount of power from the DC power bus based on the performed estimation. For example, the first motor drive unit can control the operation of the power limiting circuit based on the estimated proportional power that the first motor drive unit is entitled to obtain from the DC power bus during the on-state portion _TON of the current time period _TPBUS , and the second motor drive unit can perform the same operation. The first motor drive unit can consume the allocated (e.g., proportional) amount of the bus voltage _VBUS to drive the motor and recharge the internal energy storage element of the first motor drive unit during the on-state portion _TON of _the current time period TPBUS, and similarly, the second motor drive unit can perform the same operation. Therefore, the input current I _{_IN(B)} of the second motor drive unit can begin to increase, and the energy storage voltage V _{_ES(B)} of the energy storage element of the second motor drive unit can begin to recharge. However, at time t_₆, since the second motor drive unit is now consuming power from the DC power bus, the input current I _{_IN(A)} of the first motor drive unit can be reduced by a certain offset based on one or more other motor drive units consuming power from the DC power bus. Finally, although not shown, the energy storage element of the first motor drive unit can be slightly reduced during the off portion T_{_OFF} of the time period (e.g., between time t _₅ and time t_₆ ), and in such cases, will be recharged at the start of the on portion T_{_ON} of the next time period T _{_PBUS}.

Figure 9 is a flowchart illustrating an exemplary procedure 900, for example, to consume a distributed (e.g., proportional) amount of power from a DC power bus, which can be executed by the control circuitry of a motor drive unit (e.g., one of the motor drive units 144 of the electric roller blind 140 of Figure 1, one of the motor drive units 244 of the electric curtains 240 of Figures 2A-2C, and/or the control circuitry of the motor drive unit 500 of Figure 5). The control circuitry of the motor drive unit may execute the procedure 900 periodically (e.g., every second). The motor drive unit may be coupled to a DC power bus (e.g., DC power bus 292) and supplied with a bus voltage V_{_BUS} from a bus power supply (e.g., bus power supply 400).

The bus power supply can turn on a first controllable switch circuit and turn off a second controllable switch circuit for the on portion T_{_ON} of each time period T _{_PBUS} (e.g., 995 milliseconds), and turn off the first controllable switch circuit and turn off the second controllable switch circuit for the off portion T_{_OFF} of each time period T _{_PBUS} (e.g., five milliseconds). Therefore, the bus power supply can provide (e.g., generate) the bus voltage V _{_BUS} on the DC power bus during the on portion T_{_ON} , and can stop providing (e.g., generating) the bus voltage V_{_BUS} during the off portion T_{_OFF}.

The control circuitry of the motor drive unit can initiate program 900 at 910. At 910, the control circuitry can determine one or more operating characteristics, such as the amount of power currently used by an internal load (such as a motor), the current voltage across an energy storage element, etc. For example, the control circuitry can receive one or more internal signals (e.g., voltage) indicating the operating characteristics of the motor drive unit. For example, the control circuitry unit can determine (e.g., measure) the amount of power used by an internal load such as a motor (e.g., using a motor power signal _VPM ). The control circuitry unit can determine (e.g., measure) the voltage across an internal energy storage element of the motor drive unit (e.g., based on an energy storage element voltage signal _{VES_S} ). The control circuitry unit can determine the maximum voltage that can be stored across the internal energy storage element, which can be, for example, pre-configured in the motor drive unit (e.g., stored in its memory).

At 912, the control circuitry determines the expected amount of power the motor drive unit is expected to require during the next time period T _PBUS . The control circuitry may estimate the expected power based on the power currently used by the motor (e.g., using the motor power signal _VPM ), the voltage in the internal energy storage element (e.g., by comparing _VES with the maximum stored voltage of the internal energy storage element _{VES_MAX} ), and in some examples, one or more scaling factors. In some examples, instead of determining the voltage in the internal energy storage element, the control circuitry may determine the total storage capacity or a percentage of the maximum storage capacity of the internal energy storage element, which may not require the control circuitry to measure the voltage of the internal energy storage element (e.g., such as using a coulomb counter). The control circuitry may determine (e.g., calculate) the magnitude of the power demand current _IPR to be conducted onto the power bus. The magnitude of the power demand current _IPR may depend on (e.g., be proportional to) the power required by the motor drive unit during the next time period T _PBUS . The control circuit can estimate the power demand current IPR based on the power currently used by the motor (e.g., using the motor power signal _VPM ), the amount of voltage in the internal energy storage element (e.g., by comparing _VES with the maximum stored voltage _{VES_MAX} of the internal energy storage element), and one or more scaling factors in some examples. For example, the control circuit can estimate the power demand current _IPR based on Equation 1 _, which is mentioned above and restated below.

In some examples, the control circuitry can determine the amount of standby power P _STANDBY that the motor drive unit will request, regardless of other power requirements of the motor drive unit. For example, in some examples, the expected power amount will be no less than the standby power P _STANDBY .

At 914, the control circuitry can deliver the desired power amount to other devices on the DC power bus. For example, the control circuitry can deliver the power demand current _IPR to other devices on the DC power bus (e.g., the bus power supply, motor drive unit 500, and/or device 600). The control circuitry can use analog technology to deliver the power demand current _IPR over the DC power bus. For example, the control circuitry can use the current source control signal V _CSC to control the operation of a current source circuit (e.g., current source circuit 570) to control the amount of power demand current _IPR conducted to the DC power bus. Alternatively, the control circuitry can use digital technology over the DC power bus or use wireless or wired digital communication technology (e.g., using communication circuitry 542, such as a digital wired protocol (e.g., RS485)) to deliver the desired power amount.

At 916, the control circuitry can determine the power requirements of all other devices on the DC power bus. For example, the control circuitry can determine the total cumulative power requirements of all devices on the DC power bus during the off-period ( _TOFF ) by determining the magnitude of the DC bus voltage _VBUS during the off-period (e.g., using a scaled bus voltage _{VBUS_S} ). Alternatively, the control circuitry can determine the total power requirements of all devices on the DC power bus by receiving one or more wireless signals from other devices (e.g., using communication circuitry 542).

At 918, the control circuit can calculate a fraction of the total power that the motor drive unit can consume during the on-state portion T _ON of the next time period T _PBUS . For example, the control circuit can estimate the desired power amount as a scaled fraction of its desired power amount (e.g., based on the power demand current I _PR ) divided by the total required power of all devices on the power bus (e.g., based on the bus voltage V _BUS ).

For example, the control circuit can estimate the proportion _KP that the motor drive units of the bus power supply are allowed (e.g., allocated) to consume from the DC power bus, based on the nominal power capacity PCAP _-NOM . For example, the proportion _KP can be equal to the required power _PREQ of the motor drive units (e.g., the desired power amount determined at 912) divided by the total required power P _TOT of all motor drive units on the power bus (e.g., the required power of all devices determined at 916), for example, _KP = _PREQ / P _TOT . Equation 2

At 920, the control circuitry can calculate the amount of allocated power it can consume from the DC power bus during the on-state T_{_ON} of the next time period T_{_PBUS}. For example, the control circuitry can estimate the absolute amount of power it can consume from the DC power bus, and in some examples, scale that power to voltage. In some examples, from 910 and 920, the bus power supply can de-energize the first controllable switch circuit and energize the second controllable switch circuit (e.g., 910-920 can occur during the off-state T_{_OFF} of the time period T _{_PBUS}).

For example, the control circuit can estimate the allocated power P_{_ALLOC} that the power limiting circuit can consume from the DC power bus and/or bus capacitor C _{_BUS} (e.g., during the subsequent on-state T_{_ON}) to charge energy storage elements and/or drive the motor. The control circuit can be configured to estimate the allocated power P_{_ALLOC} by multiplying the nominal power capacity P_{_CAP-NOM} of the power supply by a proportionality K_{_P} (e.g., a fraction of the total power determined at 918).

P _ALLOC ＝K _P P _CAP-NOM 。 Equation 3

Finally, at 922, the control circuit can adjust the input current I _{_IN} of the motor drive unit based on the allocated power amount. For example, the control circuit can generate the supply voltage V_{_SUP} based on the calculated power amount it can consume from the DC power bus. For example, the control circuit can control the power limiting control signal V _{_PL} to control the power limiting circuit (e.g., power limiting circuit 552) to control the value of the supply voltage V_{_SUP} such that the value of the supply voltage V _{_SUP} is equal to (e.g., or less than) the amount of computer power that the motor drive unit can consume from the DC power bus. At 922, the bus power supply can turn on the first controllable switch circuit and turn off the second controllable switch circuit (e.g., 920 can occur during the on-state T_{_ON} of the next time period T _{_PBUS}).

For example, using analog technology, the control circuit can determine at 916 the total current _{I_TOTAL} that the motor drive unit can draw from the DC power bus, where _{I_TOTAL} = _{V_PRAD} / _{R_VAR} . Then, the control circuit can determine the allocated power _{P_ALLOC} at 918 and 920, where _{P_ALLOC} = _{P_CAP - NOM} · ( _{P_REQ} / _{P_TOTAL} ). Finally, at 922, the control circuit can determine the value of the power limiting control signal _{V_PL} used to control the input current _{I_IN} , where _{V_PL} = _{K_PL} · _{P_ALLOC} . Furthermore, using digital technology, and in some examples, the control circuit can sum the required power from all motor drive units at 916. The control circuit can then determine the allocated power _{P_ALLOC} , where at 918 and 920 _{P_ALLOC} = _PREQ / _{P_TOTAL} . Furthermore, the control circuit can determine the current limit I _LIMIT of the input current, where I _LIMIT = P _ALLOC / V _BUS , and can control the limiting circuit (e.g., power limiting circuit 552) to limit the input current to the current limit I _LIMIT at 922.

Figure 10A is a flowchart of an exemplary program 1000 that can be executed by a bus power supply, such as an overpower protection circuit (e.g., overpower protection circuit 430, overpower protection circuit 450, and/or overpower protection circuit 460) and/or a power bus management circuit of the bus power supply (e.g., power bus management circuit 440). For example, the control circuitry of the overpower protection circuitry can execute program 1000. Furthermore, in some examples, the control circuitry of the power bus management circuitry (e.g., control circuitry 448 of power bus management circuitry 440) can execute program 1000. The overpower protection circuitry can periodically execute program 1000. The overpower protection circuitry can execute program 1000 to detect and prevent overpower (e.g., overcurrent) conditions. The overpower protection circuitry can execute program 1000 to allow the bus power supply to operate at one or more increased power capacities greater than the nominal power capacity P _TH-NOM of the bus power supply for a period of time up to but not longer than the corresponding predetermined increased power period.

An overpower protection circuit can determine the magnitude of the monitored current _IMON conducted through the overpower protection circuit by sampling a current monitoring signal (e.g., a current monitoring signal VI _-MON ) at 1010. For example, the overpower protection circuit can generate the current monitoring signal VI _-MON in response to a sensed voltage across a sense resistor, through which the monitored current _IMON is conducted. The magnitude of the current monitoring signal VI _-MON can represent the magnitude of the monitored current _IMON (e.g., the current flowing from the power converter circuit to the power bus) conducted through the overpower protection circuit.

At 1012, the overpower protection circuitry can determine whether the magnitude of the current monitoring signal VI _-MON is greater than the voltage threshold VI _-TH . For example, the voltage threshold _VI-TH can be a first, second, third, or Nth voltage threshold as described herein. The voltage threshold VI _-TH can correspond to a current threshold _ITH , which indicates when the overpower protection circuitry operates at a specific power level associated with a corresponding power increase period, wherein the power converter circuitry can operate at or below the specific power level for the corresponding power increase period. For example, the voltage threshold VI _-TH can correspond to the power increase threshold of a bus power supply and can be associated with a power increase period, as mentioned herein.

If the magnitude of the current monitoring signal VI _-MON at 1012 is greater than the voltage threshold VI _-TH , the overpower protection circuit can determine at 1014 whether a timer for the voltage threshold VI _-TH is running. The timer can be based on an increased power period, which can be specific to the voltage threshold VI _-TH . For example, as mentioned herein, a first voltage threshold VI _-TH1 can be associated with a first increased power period _TIP1 (e.g., approximately 60 minutes), a second voltage threshold VI _-TH2 can be associated with a second increased power period _TIP2 (e.g., approximately 2 minutes), and so on. In some examples, the timer can be implemented as a threshold comparison and timing circuit (e.g., threshold comparison and timing circuits 456a-465n), a timer (e.g., timers 484, 490), and/or as a timer as part of control circuitry. If the timer for VI _-TH is not running at 1014, the overpower protection circuit can initiate (e.g., set) the timer for the voltage threshold VI _-TH at 1024 before returning to 1010. For example, a timer can be configured to start with a timer value that increments from zero and run for an increasing power period associated with the corresponding power level (e.g., or count down to zero from the increasing power period).

If the timer for VI _-TH is running at 1014, the overpower protection circuit can determine at 1016 whether the timer for VI _-TH has expired (e.g., whether the period of increased power associated with the corresponding power level has elapsed). For example, at 1016, the overpower protection circuit can compare the timer value with a timer threshold (e.g., which could be the period of increased power associated with the corresponding increased power level), and if the timer value reaches or exceeds the timer threshold, determine that the timer has expired. Alternatively, the timer can be a decrementing timer, and at 1016, the overpower protection circuit can determine that the timer has expired when the timer value reaches zero.

If the timer expires at 1016, the overpower protection circuit can disconnect the power converter circuit from the power bus at 1018 and exit program 1000, for example, by deactivating the controllable switch circuit (e.g., by deactivating controllable switch circuits 454 or 464). Therefore, by executing program 1000, the overpower protection circuit is configured to disconnect the power converter circuit from the power bus when the value of the monitored current _IMON exceeds the current threshold for the duration of the increased power period associated with the corresponding increased power threshold.

If at 1016 the timer has not yet expired, the overpower protection circuit can return to 1010 to sample the current monitoring signal VI _-MON again. For example, the current monitoring signal _VI-MON can continue to exceed the threshold until the timer expires, or the current monitoring signal VI _-MON can stop exceeding the threshold before the timer expires. If at 1012 the value of the current monitoring signal VI _-MON is not greater than the voltage threshold VI _-TH , then at 1020, the overpower protection current can determine whether the timer is already running. If the timer is already running, the overpower protection circuit can stop and reset the corresponding timer for the voltage threshold VI _-TH and exit program 1000. If at 1020 the timer for the voltage threshold VI _-TH is not yet running, the overpower protection circuit can exit program 1000.

The entire procedure 1000 can be repeated (e.g., in parallel and/or sequentially) for multiple power increase thresholds and/or power increase time periods. For example, the power levels may correspond to various power levels of the bus power supply, and each power increase threshold may be associated with a corresponding time period. Thus, procedure 1000 may allow the bus power supply to operate with one or more power increase capacities greater than the nominal power capacity _PTH-NOM of the bus power supply for a period of time up to but not longer than the corresponding predetermined power increase time period. Furthermore, procedure 1000 may allow the overpower protection circuitry to assess whether the value of the monitored current _IMON has been operating at or below multiple different power increase thresholds (e.g., exceeding multiple different corresponding current thresholds) for the corresponding power increase time period.

In some examples, after determining at 1012 that the magnitude of the current monitoring signal VI _-MON is greater than the voltage threshold VI _-TH , the overpower protection circuit may send a message (e.g., analog signal, digital message, etc.) to one or more motor drive units, the message indicating that the magnitude of the output power of the bus power supply exceeds the nominal power capacity PTH _-NOM of the bus power supply and/or requiring one or more motor drive units to gradually reduce their power consumption to avoid future tripping.

Figure 10B is a flowchart of an exemplary program 1050 that can be executed by a bus power supply, such as a power bus management circuit (e.g., power bus management circuit 440). For example, the control circuitry of the power bus management circuitry (e.g., control circuitry 448 of power bus management circuitry 440) can execute program 1050. The control circuitry can periodically execute program 1050. The control circuitry can execute program 1050 to allow the bus power supply to operate at one or more increased power capacities greater than the nominal power capacity _PTH-NOM of the bus power supply for up to, but not longer than, a corresponding predetermined increased power time period. For example, the control circuitry can execute program 1050 to adjust the resistance _RVAR of a sensing resistor (e.g., variable resistor 446) to, for example, adjust the determined (e.g., estimated) allocated power _PALLOC by each of the motor drive units on the power bus to prevent the output power _POUT of the bus power supply from exceeding an increased power threshold for a corresponding increased power time period exceeding that threshold. The control circuit can be configured to control the resistance R _VAR of the variable resistor between the minimum resistance R _MIN and the nominal resistance R _NOM (e.g., the maximum resistance).

The control circuitry can sample the current sensing signal VI _-SENSE at 1060. The current sensing signal VI _-SENSE can have a magnitude indicating the magnitude of the sensed current _IsENSE conducted through the sense resistor (e.g., variable resistor 446) of the power bus management circuitry. For example, the current sensing signal VI _-SENSE can indicate, for example, the total current ITOTAL conducted on the power bus during the off-period _TOFF period of a periodic time (e.g., when the first controllable switch circuit 442 is not conducting and the second controllable switch circuit 444 is _conducting ).

At 1062, the control circuit can determine the total required current _IREQ-TOTAL based on the current sensing signal VI _-SENSE . The total required current _IREQ-TOTAL can be equal to, for example, the total value of the power demand current _IPR conducted to the power bus by multiple motor drive units coupled to the power bus during the off-period _TOFF of a periodic time period. As mentioned above, the value of the power demand current _IPR can depend on (e.g., requested) power _PREQ of the motor drive unit (e.g., proportional to it), and therefore the total required current _IREQ-TOTAL can be equal to the total power demand of all motor drive units coupled to the power bus.

At 1064, the control circuitry determines whether the total required current I _{_REQ-TOTAL} is greater than the voltage threshold VI _-TH . As described herein, the voltage threshold VI _-TH1 may correspond to the current threshold I _{_TH1} and/or the power threshold P_{_TH} . In some examples, the voltage threshold VI _-TH may be a first, second, third, or Nth voltage threshold as described herein. In such examples, the voltage threshold VI _-TH may correspond to the increased power threshold of the bus power supply and may be associated with the increased power period, as mentioned herein. However, in other examples, the voltage threshold VI _-TH may be configured to be slightly less than the first, second, third, or Nth voltage threshold.

If the total required current I _{_REQ-TOTAL} at 1064 is greater than the voltage threshold VI _-TH , the control circuit can determine at 1066 whether a timer for the voltage threshold VI _-TH is running. The timer can be specific to the voltage threshold VI _-TH . In some examples, the timer can be configured to be slightly smaller than the timer used for the power increase period. For example, a first voltage threshold VI _-TH1 can be associated with a first time period T_{_IP1} (e.g., approximately 58 minutes, which is slightly less than 60 minutes), a second voltage threshold VI _-TH2 can be associated with a second time period T _{_IP2} (e.g., approximately 1 minute and 50 seconds, which is slightly less than 2 minutes), and so on. Therefore, the timer used in program 1050 can be configured to expire before the timer used in program 1000.

If the timer for VI _-TH is not running at 1066, the control circuit can start (e.g., set) the timer for the voltage threshold VI _-TH at 1072. At 1074, the control circuit can control the resistance R_{_VAR} of the variable resistor to increase the power capacity of the bus power supply. For example, the control circuit can decrease the resistance R_{_VAR} of the variable resistor so that it appears to the motor drive unit that the total cumulative power required by all motor drive units has been reduced, which can cause the allocated power P _{_ALLOC} of each motor drive unit to increase during the next on-time portion of the periodic time period. After controlling the resistance R_{_VAR} of the variable resistor at 1074, the control circuit can return to 1060. However, in some examples, 1074 can be omitted, and the control circuit can be configured to return to 1060 after starting the timer at 1072.

If the timer for VI _-TH is running at 1066, the control circuit can determine at 1068 whether the timer for VI _-TH has expired. If the timer has expired at 1068, the control circuit can control the resistance R _{_VAR} of the variable resistor to reduce the power capacity of the bus power supply. For example, the control circuit can reduce the resistance R_{_VAR} of the variable resistor so that it appears to the motor drive units that the total cumulative power required by all motor drive units has increased, which can cause the allocated power P _{_ALLOC} of each motor drive unit to decrease during the next on-time portion of the periodic time period. Therefore, by executing program 1050, the control circuit can be configured to adjust the resistance R _{_VAR} of the variable resistor to adjust the power capacity of the bus power supply, for example, adjusting the allocated power P _{_ALLOC} determined (e.g., estimated) by each of the motor drive units on the power bus, to prevent the output power P _{_OUT} of the bus power supply from exceeding the increased power threshold for the corresponding increased power time period exceeding that increased power threshold.

If the timer has not expired at point 1068, the control circuit can return to point 1060 to sample the current sensing signal VI _-SENSE again. For example, the total required current I _REQ-TOTAL can continue to exceed the voltage threshold VI _-TH until the timer expires, or the total required current I _REQ-TOTAL can stop exceeding the threshold before the timer expires. If at point 1064, the total required current I _REQ-TOTAL is not greater than the voltage threshold VI _-TH , then at point 1076, the control current can determine whether the timer is already running. If the timer is already running, the control circuit can stop and reset the corresponding timer for the voltage threshold VI _-TH at point 1078 and exit program 1050. If at point 1076, the timer for the voltage threshold VI _-TH is not yet running, the control circuit can exit program 1050.

The entire procedure 1050 can be repeated (e.g., in parallel and/or sequentially) for multiple thresholds and/or time periods, wherein, for example, each of the thresholds and/or time periods may be slightly smaller than the power increase threshold and/or power increase time period described herein (e.g., to ensure that the control circuit has the ability to adjust the variable resistance R _VAR of the variable resistor before the overpower protection circuit trips).

Figure 11 is a block diagram of an exemplary DC power distribution system 1100. The DC power distribution system 1100 may include (e.g., an electric roller blind 140) one or more motorized curtains 1150. For example, each of the motorized curtains 1150 may include a corresponding motor drive unit 1152 configured to adjust the position of a corresponding covering material 1154 to control the amount of daylight entering the building through the corresponding window.

The DC power distribution system 1100 may include a DC power bus 1140 (e.g., a Class 2 power bus) and may be daisy-chained electrically coupled to the motor drive units 1152. The DC power distribution system 1100 may also include a bus power supply 1110 (e.g., a Class 2 protected power supply) configured to provide a protected supply voltage _{VPS_PRT} to the motor drive units 1152 via the DC power bus 1140. Although shown as four motor drive units 1152, in some examples, more or fewer motor drive units 1152 may be coupled to the DC power bus 1140.

Each motor drive unit 1152 may include one or more power connectors, diodes and bus capacitors, control circuitry, communication circuitry, a user interface, a power supply, motor drive circuitry, rotational position sensing circuitry, and/or a motor. Additionally, the motor drive unit 1152 may include power converter circuitry to convert the protected supply voltage _{VPS_PRT} into a motor voltage for driving the motor. However, the motor drive unit 1152 may not include any energy storage element (e.g., energy storage element 555, such as one or more supercapacitors, rechargeable batteries, or other suitable energy storage devices) and associated circuitry, such as power limiting circuitry, charging circuitry, current sources, and controllable switching circuitry coupled between the energy storage element and the power connector. For example, each of the motor drive units 1152 may be similar to the motor drive unit 500 of FIG. 6, but excluding one or more of the power limiting circuitry 552, charging circuitry 553, energy storage element 555, current source 570, controllable switching circuitry 560, and scaling circuitry. Therefore, in the absence of the energy storage element 555, the motor drive unit 1150 may be forced to consume all the power required to drive its internal motor from the bus power supply 1110 during movement (e.g., it may lack the ability to consume the power required to power a predetermined number of complete movements, such as fewer than or equal to 10 complete movements).

Bus power supply 1110 may be electrically coupled to one or more of motor drive units 1152 via DC power bus 1140. For example, bus power supply 1110 may include one or more power connectors (e.g., power connector 410, which may include two power terminals, such as a positive terminal and a negative terminal) for receiving input voltage from an external power supply (e.g., an AC trunk supply for receiving AC trunk line voltage _VAC ). Bus power supply 1110 may also include a power connector (e.g., power connector 412) connected to DC power bus 1140, which is electrically coupled to one or more motor drive units 1152. Bus power supply 1110 may be configured to generate a protected supply voltage _{VPS_PRT} , and power connector 412 may provide the protected supply voltage _{VPS_PRT} to DC power bus 1140. Motor drive units 1152 connected to DC power bus 1140 may conduct output current from bus power supply 1110 through the output of the power connector of bus power supply 1110.

Bus power supply 1110 may include power converter circuitry 1120 coupled to an input power connector for receiving an input voltage (e.g., AC trunk line voltage V _{_AC} ) and for generating a direct current (DC) supply voltage V _{_{PS_DC}} . Power converter circuitry 1120 may be an example of power converter circuitry 420 of bus power supply 400. Power converter circuitry 1120 may be an AC/DC converter or a DC/DC converter, depending on whether bus power supply 1110 is connected to an AC or DC power source.

Bus power supply 1110 may include overpower protection circuitry 1130, configured to receive a DC supply voltage _{VPS_DC} and output a protected supply voltage _{VPS_PRT} under normal conditions. Bus power supply 1110 may also disconnect power converter 1120 from DC power bus 1140 (e.g., disable bus power supply 1110) in response to power converter 1120's output power exceeding a threshold. Overpower protection circuitry 1130 may be an example of overpower protection circuitry 430 of bus power supply 400.

As mentioned above regarding the overcurrent protection circuit 430, the overpower protection circuit 1130 can monitor the output power of the bus power supply 1110 (e.g., because the protected supply voltage _{VPS_PRT} has a DC value) by monitoring the current conducted through the overpower protection circuit 1130 (e.g., the monitored current _IMON ). For example, the overpower protection circuit 1130 may have multiple timing thresholds, each associated with a different power level and a corresponding time amount. In some examples, the overpower protection circuit 1130 may be configured to disconnect the power converter circuit 1120 from the DC power bus 1140 by opening a switch (e.g., a controllable conductive switch circuit). Furthermore, the overpower protection circuit 1110 may be configured to keep the power converter circuit 1120 disconnected from the DC power bus until, for example, the power to the bus power supply 1110 has been fully cycled (e.g., the bus power supply 1110 has been turned on and off again) or the power to the bus power supply 1110 has been removed (e.g., the bus power supply 1110 has been turned off) and then restored.

It should be noted that the bus power supply 1110 may not include power bus management circuitry, such as the power bus management circuitry 440 of the bus power supply 400. Therefore, the bus power supply 1110 may be the same as the bus power supply 400, except that the bus power supply 1110 does not include the power bus management circuitry 440.

Figure 12 is an exemplary waveform 1200, illustrating the output power of the bus power supply 1110 when connected to a DC power bus 1140 in a DC power distribution system 1100 comprising multiple (e.g., four) motor drive units 1152. As mentioned above, the motor drive units 1152 may not be able to store sufficient power for multiple full operations of the motors without drawing a higher amount of current directly from the DC power bus 1140. Also, as mentioned above, the bus power supply 1110 may include an overpower protection circuit 1130. During periods when no motor drive units 1152 are driving their internal motors, the output power of the bus power supply may be at a standby power _PSB level (e.g., 0.5 watts or 1 watt per motor drive unit, totaling 1.6 watts, 2 watts, or 4 watts). The standby power _PSB may represent the combined nominal or standby power consumed by the motor drive units 1152 connected to the DC power bus 1140 when the motor drive units 1152 are not driving their internal motors.

When each of the motor drive units 1152 receives a command to raise its respective covering material 1154 from the fully lowered position to the fully raised position, the motor drive units 1152 can be configured to move the covering material 1154 together. The time period taken for all the motor drive units 1150 to raise their motorized curtains from the fully lowered position to the fully raised position can be represented by the movement time period T _MOVE (e.g., approximately 60 seconds). For example, at time _t1 , the motorized curtains of each of the motor drive units 1150 may be in the fully lowered position, and all the motor drive units 1150 may start driving their motors in response to receiving the command. And at time _t2 , all the motor drive units 1150 may stop driving their motors and the motorized curtains may be in the fully raised position.

As shown in Table 1200, during the movement period T _MOVE , the output power of the bus power supply 1110 may exceed the nominal power level, but may remain below the maximum power increase threshold (e.g., 240 watts) of the bus power supply 1110. It should be noted that this is true even though the motor drive unit 1150 does not include an internal energy storage element capable of storing sufficient power for multiple complete operations of the motor, and therefore, the bus power supply 1110 supplies full power to drive the corresponding motor of the motor drive unit 1150 connected to the DC power bus. Furthermore, it should be understood that the output power of the bus power supply 1110 is highest when the motorized curtains approach the fully lowered position and decreases as they rise towards the fully raised position. Therefore, during the movement period T _MOVE , the output power of the bus power supply 1110 may not exceed the nominal power level (e.g., 85 watts) of the bus power supply 1110 for more than the first power increase period (e.g., 60 minutes), and also may not exceed the first power increase threshold (e.g., 150 watts) for more than the second power increase period (e.g., 2 minutes). Therefore, even if multiple (e.g., four) motor drive units 1150 all drive their motors simultaneously, the overpower protection circuit 1130 of the bus power supply 1110 will not trip.

Although not shown, the combined power required to simultaneously lower all motor drive units 1150 of the motorized curtains is less than the combined power required to raise all motor drive units 1150 of the motorized curtains. For example, when lowering the motorized curtains, motor drive units 1150 can drive motors to slow the rate at which the motorized curtains are lowered due to gravity. That is, gravity would cause the motorized curtains to descend faster, but motors are used to break and maintain the descent as a more constant motion. Therefore, the output power of bus power supply 1110 is less when all motorized curtains are lowered simultaneously than when they are raised. Thus, even if all motor drive units 1152 of the motorized curtains are raised and lowered in a consistent and repetitive manner, the output power of bus power supply 1110 will not exceed the maximum power increase threshold (e.g., 240 watts), may not exceed the nominal power level of the bus power supply (e.g., 85 watts) for more than a first power increase period (e.g., 60 minutes), and may not exceed the first power increase threshold (e.g., 150 watts) for more than a second power increase period (e.g., 2 minutes). Furthermore, the average output power that completes the rise and subsequent fall may (e.g., may always) be lower than the nominal continuous power level of the bus power supply 1110 (e.g., 85 watts).

Although described using the motor drive unit 1152 of the motorized curtain 1150, the bus power supply 1110 of the DC power distribution system 1100 shown in FIG11 can be configured to power other types of periodic loads, such as high-power sensors including sensing circuitry (e.g., occupancy sensing circuitry with higher power handling capabilities, such as radar), periodic light sources such as LED drivers and lighting loads, light sources that consume high power over short periods of time (e.g., ballasts that require more power when illuminating a light than during steady-state operation, lighting loads located in infrequently visited locations (such as closets), lighting loads on short-time clocks or timers (such as external lighting loads triggered by motion, events, or at a predetermined time of day), motorized room dividers, cameras (e.g., configured to detect glare at one or more windows, detect occupants, etc.), and/or similar items. Furthermore, the motor drive unit 1152 can each drive any type of motor for any purpose, such as a motor for a condenser, a burner for a furnace, etc.

Claims (124)

1. A drive unit for use in a power distribution system including a bus power supply and a plurality of drive units, the drive unit comprising: A power limiting circuit, configured to conduct current from the power bus and generate a supply voltage; A load circuit configured to receive the supply voltage and control the power delivered to the electrical load; and Control circuit, the control circuit being configured to: The allocated power that each drive unit can consume from the power bus is determined based on the power required by the drive unit, the cumulative total power required by the plurality of drive units, and the power capacity of the bus power supply; and The power limiting circuit is controlled to consume the allocated power from the power bus. 2. The driving unit as claimed in claim 1, further comprising: An internal energy storage element is configured to store sufficient power for multiple operations of the load circuit; and The amount of power required by the drive unit is based on the amount of power required by the load circuit to supply power to the electrical load and the voltage across the internal energy storage element. 3. The drive unit of claim 1, wherein the control circuit is configured to: The proportional power amount for the drive unit is determined based on the power required by the drive unit and the cumulative total power required by the plurality of drive units; and The allocated power amount is determined based on the proportional power amount for the drive unit and the power capacity of the bus power supply. 4. The drive unit of claim 1, wherein the control circuit is configured to determine the cumulative total power required by the plurality of drive units based on the magnitude of the current conducted from the plurality of drive units to the power bus. 5. The drive unit of claim 1, wherein the bus power supply is configured to provide a bus voltage on the power bus during an on-phase portion of a periodic time period, and is configured not to provide the bus voltage on the power bus during an off-phase portion of the periodic time period; and The control circuitry is configured to measure the magnitude of the bus voltage across the power bus during the off portion of the periodic time period, wherein the magnitude of the bus voltage across the power bus indicates the cumulative total power required by the plurality of drive units. 6. The drive unit of claim 5, wherein the control circuit is configured to: During the off portion of the periodic time period, a power demand current is conducted to the power bus, wherein the magnitude of the power demand current is proportional to the amount of power required by the drive unit. Measure the magnitude of the bus voltage across the power bus during the off portion of the periodic time period; The proportion of the power capacity of the bus power supply that the drive unit can consume during the next on-phase of the periodic time is estimated based on the power required by the drive unit and the magnitude of the bus voltage across the power bus during the off-phase of the periodic time; and The power limiting circuit is controlled to consume the allocated power from the power bus during the next on-time portion of the periodic time period, wherein the allocated power is determined based on the proportional amount that the drive unit is capable of consuming multiplied by the power capacity of the bus power supply. 7. The drive unit of claim 6, wherein the control circuit is configured to determine the amount of power required by the drive unit based on the power required by the drive unit to supply power to the electrical load, to charge the internal energy storage element of the motor drive unit, and the standby power consumption of the motor drive unit. 8. The drive unit of claim 6, wherein the magnitude of the bus voltage across the power bus represents the cumulative total power required by the plurality of drive units. 9. The drive unit of claim 1, wherein the control circuitry is configured to signal the required power amount to the bus power supply before controlling the power limiting circuitry to consume the allocated power amount from the power bus. 10. The drive unit of claim 1, wherein the drive unit includes communication circuitry, and wherein the control circuitry is configured to determine the cumulative total power required by the plurality of drive units based on one or more digital messages received via the communication circuitry. 11. The drive unit of claim 1, wherein the drive unit includes a motor drive unit for electric curtains; The load circuit includes a motor drive circuit for a motor configured to control the movement of the covering material of the motorized curtains to control the amount of daylight entering the space; and The motor drive circuit is powered by the supplied voltage. 12. A system comprising: Multiple drive units according to claim 1; and A bus power supply, the bus power supply including a power converter configured to generate a bus voltage on the power bus, wherein the bus power supply has a power capacity that defines a maximum amount of power that the bus power supply can deliver through the power bus. 13. The system of claim 12, wherein the bus power supply is characterized by defining a nominal power capacity that defines a nominal power threshold, wherein the bus power supply is capable of supplying power to the plurality of drive units indefinitely when equal to or below the nominal power threshold, wherein the nominal power threshold is less than the maximum power amount defined by the power capacity of the bus power supply. 14. The system of claim 13, wherein the bus power supply is configured to continuously supply power to the power bus at a power level equal to or below the nominal power threshold without being interrupted or disconnected by the overpower protection circuitry of the bus power supply. 15. The system of claim 13, wherein the bus power supply is configured to supply power to the plurality of drive units at one or more additional power capacities greater than the nominal power capacity for a period of time up to but not longer than a corresponding predetermined additional power time period. 16. The system of claim 15, wherein the bus power supply includes a power converter circuit and an overpower protection circuit, wherein the overpower protection circuit is configured to disconnect the bus voltage from the power bus in response to the output power of the power converter circuit exceeding a first power increase threshold for a period of time exceeding a first power increase threshold, and is configured to disconnect the bus voltage from the power bus in response to the output power of the power converter circuit exceeding a second power increase threshold for a period of time exceeding a second power increase threshold. 17. The system of claim 15, wherein the bus power supply includes a variable resistor, and the bus power supply is configured to adjust the variable resistance of the variable resistor to adjust the estimated power distribution of each of the motor drive units on the power bus. 18. The system of claim 17, wherein the increase in the variable resistor causes the control circuit of each of the plurality of drive units to determine that the cumulative total power required by the plurality of drive units has increased. 19. The system of claim 12, wherein the bus power supply comprises: First controllable switching circuit; A second controllable switch circuit, wherein the second controllable switch circuit is coupled between the connection point of the first controllable switch circuit and the common terminal of the circuit through the sensing resistor; and Control circuit, the control circuit being configured to: For the on portion of the periodic time period, the first controllable switch circuit is turned on and the second controllable switch circuit is turned off, so as to provide the bus voltage on the power bus during the on portion of the periodic time period; and for the off portion of the periodic time period, the first controllable switch circuit is turned off and the second controllable switch circuit is turned off, so as to not provide the bus voltage on the power bus during the off portion of the periodic time period. Measure the total voltage across the power bus during the off portion of the periodic time period; and The total power requirement of multiple devices is determined based on the measurement results. 20. The system of claim 19, further comprising: A first power connector and a second power connector, the first power connector being used to receive an input voltage from an external power supply, the second power supply being configured to connect to the power bus, wherein the bus is configured to be electrically coupled to the plurality of devices; The first controllable switch circuit is coupled between the output terminal of the power converter and the second power connector; and The second controllable switch circuit is coupled between the connection point of the first controllable switch circuit and the second power connector and the common terminal of the circuit through the sensing resistor, wherein the second controllable switch circuit and the sensing resistor are coupled in parallel between the terminals of the second power connector. 21. A load control system for controlling multiple electrical loads, the load control system comprising: A bus power supply, the bus power supply including a power converter configured to generate a bus voltage on a power bus, wherein the bus power supply has a power capacity defining a maximum amount of power that the bus power supply can deliver via the power bus; and Multiple drive units, wherein each drive unit includes: A power limiting circuit, configured to conduct current from the power bus and generate a supply voltage; A load circuit configured to receive the supply voltage and control the power delivered to the electrical load; and Control circuit, the control circuit being configured to: The allocated power that each drive unit can consume from the power bus is determined based on the power required by the drive unit, the cumulative total power required by the plurality of drive units, and the power capacity of the bus power supply; and The power limiting circuit is controlled to consume the allocated power from the power bus. 22. The load control system of claim 21, wherein each drive unit further includes an internal energy storage element configured to store sufficient power for multiple operations of the load circuit; and The amount of power required by the drive unit is based on the amount of power required by the load circuit to supply power to the electrical load and the voltage across the internal energy storage element. 23. The load control system of claim 21, wherein the control circuit of each of the drive units is configured to: The proportional power amount for the drive unit is determined based on the power required by the drive unit and the cumulative total power required by the plurality of drive units; and The allocated power amount is determined based on the proportional power amount for the drive unit and the power capacity of the bus power supply. 24. The load control system of claim 21, wherein the control circuit of each of the plurality of drive units is configured to determine the cumulative total power required by the plurality of drive units based on the magnitude of the current conducted from the plurality of drive units to the power bus. 25. The load control system of claim 21, wherein the bus power supply is configured to provide the bus voltage on the power bus during the on-phase of a periodic time period and is configured not to provide the bus voltage on the power bus during the off-phase of the periodic time period. 26. The load control system of claim 25, wherein the control circuit of each of the drive units is configured to measure the magnitude of the bus voltage across the power bus during the off portion of the periodic time period, wherein the magnitude of the bus voltage across the power bus indicates the cumulative total power required by the plurality of drive units. 27. The load control system of claim 25, wherein the drive unit includes communication circuitry, and wherein the control circuitry of each of the drive units is configured to receive a message from each of the plurality of drive units via the power bus during the off-period of the periodic time period, wherein each message indicates a required power for one of the plurality of drive units. 28. The load control system of claim 25, wherein the control circuit of each of the drive units is configured to: During the off portion of the periodic time period, a power demand current is conducted to the power bus, wherein the magnitude of the power demand current is proportional to the amount of power required by the drive unit. Measure the magnitude of the bus voltage across the power bus during the off portion of the periodic time period; The proportion of the power capacity of the bus power supply that the drive unit can consume during the next on-phase of the periodic time is estimated based on the power required by the drive unit and the magnitude of the bus voltage across the power bus during the off-phase of the periodic time; and The power limiting circuit is controlled to consume the allocated power from the power bus during the next on-time portion of the periodic time period, wherein the allocated power is determined based on the proportional amount that the drive unit is capable of consuming multiplied by the power capacity of the bus power supply. 29. The load control system of claim 28, wherein the control circuit of each of the drive units is configured to determine the amount of power required by the drive unit based on the power required by the drive unit to supply power to the electrical load, to charge the internal energy storage element of the motor drive unit, and the standby power consumption of the motor drive unit. 30. The load control system of claim 28, wherein the magnitude of the bus voltage across the power bus during the off portion of the periodic time period represents the cumulative total power required by the plurality of drive units. 31. The load control system of claim 21, wherein the bus power supply includes an overcurrent protection circuit configured to disconnect the power converter circuit from the power bus in response to the magnitude of the bus current of the power bus exceeding a first current threshold for a first time period or exceeding a second current threshold for a second time period. 32. The load control system of claim 21, wherein the control circuit of each of the drive units is configured to signal the required power amount of the drive unit to the bus power supply before controlling the power limiting circuit to consume the allocated power amount from the power bus. 33. The load control system of claim 21, wherein the drive unit includes communication circuitry, and wherein the control circuitry is configured to determine the cumulative total power required by the plurality of drive units based on one or more digital messages received via the communication circuitry. 34. The load control system of claim 21, wherein each of the plurality of drive units is a motor drive unit for an electric curtain; The load circuit includes a motor drive circuit for a motor configured to control the movement of the covering material of the motorized curtains to control the amount of daylight entering the space; and The motor drive circuit is powered by the supplied voltage. 35. The load control system of claim 21, wherein the bus power supply is characterized by a nominal power capacity that defines a nominal power threshold, wherein the bus power supply is capable of supplying power to the plurality of drive units indefinitely when equal to or below the nominal power threshold, wherein the nominal power threshold is less than the maximum power amount defined by the power capacity of the bus power supply. 36. The load control system of claim 35, wherein the bus power supply is configured to continuously supply power to the power bus at a power level equal to or below the nominal power threshold without being interrupted or disconnected by the overpower protection circuitry of the bus power supply. 37. The load control system of claim 35, wherein the bus power supply is configured to supply power to the plurality of drive units at one or more additional power capacities greater than the nominal power capacity for a period of time up to but not longer than a corresponding predetermined additional power period. 38. The load control system of claim 37, wherein the bus power supply includes a power converter circuit and an overpower protection circuit, wherein the overpower protection circuit is configured to disconnect the bus voltage from the power bus in response to the output power of the power converter circuit exceeding a first power increase threshold for a period of time exceeding a first power increase threshold, and is configured to disconnect the bus voltage from the power bus in response to the output power of the power converter circuit exceeding a second power increase threshold for a period of time exceeding a second power increase threshold. 39. The load control system of claim 37, wherein the bus power supply includes a variable resistor, and the bus power supply is configured to adjust the variable resistance of the variable resistor to adjust the estimated distributed power of each of the motor drive units on the power bus. 40. The load control system of claim 39, wherein the increase in the variable resistor causes the control circuit of each of the plurality of drive units to determine that the cumulative total power required by the plurality of drive units has increased. 41. A load control system for controlling multiple electrical loads, the load control system comprising: A bus power supply, comprising a power converter, wherein the bus power supply is configured to generate a bus voltage on a power bus during an on-phase portion of a periodic time period and is configured not to generate the bus voltage on the power bus during an off-phase portion of the periodic time period, wherein the bus power supply has a power capacity defining a maximum amount of power that the bus power supply can deliver via the power bus; and Multiple drive units, wherein each drive unit includes: A power limiting circuit, configured to conduct current from the power bus and generate a supply voltage; Internal energy storage components; A load circuit configured to receive the supply voltage and control the power delivered to the electrical load; and Control circuit, the control circuit being configured to: Determine the amount of power required by the drive unit to supply power to the electrical load and to charge the internal energy storage element; During the off portion of the periodic time period, a power demand current is conducted to the power bus, wherein the magnitude of the power demand current is proportional to the amount of power required by the drive unit. Measure the magnitude of the bus voltage across the power bus during the off portion of the periodic time period; The proportion of the power capacity of the bus power supply that the drive unit can consume during the next on-phase of the periodic time is estimated based on the power required by the drive unit and the magnitude of the bus voltage across the power bus during the off-phase of the periodic time; and The power limiting circuit is controlled to consume the proportional amount of power from the power bus during the next on-time portion of the periodic time period, wherein the allocated power amount is determined based on the proportional amount that the drive unit is capable of consuming multiplied by the power capacity of the bus power supply. 42. The load control system of claim 41, wherein the magnitude of the bus voltage across the power bus represents the cumulative total power required by the plurality of drive units. 43. The load control system of claim 41, wherein the control circuit of each of the drive units is configured to determine the amount of power required by the drive unit based on the power required by the drive unit to supply power to the electrical load, to charge the internal energy storage element of the motor drive unit, and the standby power consumption of the motor drive unit. 44. The load control system of claim 41, wherein the control circuit of each of the drive units is configured to consume the proportional power from the power bus to drive the electrical load and recharge the internal energy storage element of the drive unit. 45. The load control system of claim 41, wherein the bus power supply further comprises a first controllable switching circuit, a second controllable switching circuit, and a sensing resistor; and During the on-time portion of the periodic time period, the bus power supply is configured to turn on the first controllable switch circuit and turn off the second controllable switch circuit, and during the off-time portion of the periodic time period, the first controllable switch circuit and the second controllable switch circuit are both turned off. 46. The load control system of claim 41, wherein the control circuit of each of the drive units is configured to estimate the power demand current based on the power being used by the electrical load and the voltage in the internal energy storage element. 47. The load control system of claim 46, wherein the control circuit of each of the drive units is configured to further estimate the power demand current based on the standby power consumption of the motor drive unit. 48. The load control system of claim 46, wherein the control circuit of each of the drive units is configured to determine the voltage amount in the internal energy storage element based on the difference between the magnitude of the stored voltage of the internal energy storage element and the maximum stored voltage of the internal energy storage element. 49. The load control system of claim 41, wherein the control circuitry is configured to measure the total voltage across the power bus after the start of the shutdown portion of the periodic time period. 50. The load control system of claim 41, wherein the control circuit is configured to determine the occurrence of the shutdown portion of the periodic time when the magnitude of the bus voltage drops below a threshold. 51. The load control system of claim 41, wherein the bus power supply is characterized by a nominal power capacity that defines a nominal power threshold, wherein the bus power supply is capable of supplying power to the plurality of drive units indefinitely when equal to or below the nominal power threshold, wherein the nominal power threshold is less than the maximum power amount defined by the power capacity of the bus power supply. 52. The load control system of claim 51, wherein the bus power supply is configured to continuously supply power to the power bus at a power level equal to or below the nominal power threshold without being interrupted or disconnected by the overpower protection circuitry of the bus power supply. 53. The load control system of claim 51, wherein the bus power supply is configured to supply power to the plurality of drive units at one or more additional power capacities greater than the nominal power capacity for a period of time up to but not longer than a corresponding predetermined additional power period. 54. The load control system of claim 53, wherein the bus power supply includes a power converter circuit and an overpower protection circuit, wherein the overpower protection circuit is configured to disconnect the bus voltage from the power bus in response to the output power of the power converter circuit exceeding a first power increase threshold for a period of time exceeding a first power increase threshold, and is configured to disconnect the bus voltage from the power bus in response to the output power of the power converter circuit exceeding a second power increase threshold for a period of time exceeding a second power increase threshold. 55. The load control system of claim 53, wherein the bus power supply includes a variable resistor, and the bus power supply is configured to adjust the variable resistance of the variable resistor to adjust the estimated distributed power of each of the motor drive units on the power bus. 56. The load control system of claim 55, wherein the increase in the variable resistor causes the control circuit of each of the plurality of drive units to determine that the cumulative total power required by the plurality of drive units has increased. 57. The load control system of claim 55, wherein the bus power supply is configured to adjust the variable resistance of the variable resistor to allow the plurality of drive units to consume a power amount greater than the nominal power threshold on the power bus. 58. The load control system of claim 55, wherein the bus power supply is configured to adjust the variable resistance of the variable resistor such that the plurality of drive units consume a power amount less than or equal to the nominal power threshold on the power bus. 59. The load control system of claim 53, wherein the bus power supply includes a current source, and the bus power supply is configured to conduct current to the power bus during the off-period of the periodic time period to adjust the estimated power distribution of each of the motor drive units on the power bus. 60. The load control system of claim 41, wherein each of the plurality of drive units is a motor drive unit for an electric curtain; Each of the plurality of load control devices includes a load circuit for a motor drive circuit, the motor being configured to control the movement of the covering material of the motorized curtains to control the amount of daylight entering the space; and The motor drive circuit is powered by the supplied voltage. 61. A bus power supply for providing a bus voltage to a plurality of devices, the bus power supply comprising: First controllable switching circuit; A second controllable switch circuit, wherein the second controllable switch circuit is coupled between the connection point of the first controllable switch circuit and the common terminal of the circuit through the sensing resistor; and Control circuit, the control circuit being configured to: For the on portion of the periodic time period, the first controllable switch circuit is turned on and the second controllable switch circuit is turned off, so as to provide the bus voltage on the power bus during the on portion of the periodic time period; and for the off portion of the periodic time period, the first controllable switch circuit is turned off and the second controllable switch circuit is turned off, so as to not provide the bus voltage on the power bus during the off portion of the periodic time period. Measure the total voltage across the power bus during the off portion of the periodic time period; and The total power requirement of the plurality of devices is determined based on the measurement results. 62. The bus power supply of claim 61, further comprising: A first power connector and a second power connector, the first power connector being used to receive an input voltage from an external power supply, the second power supply being configured to connect to the power bus, wherein the bus is configured to be electrically coupled to the plurality of devices. 63. The bus power supply of claim 62, wherein the first controllable switching circuit is coupled between the output of the power converter and the second power connector; and The second controllable switch circuit is coupled between the connection point of the first controllable switch circuit and the second power connector and the common terminal of the circuit through the sensing resistor, wherein the second controllable switch circuit and the sensing resistor are coupled in parallel between the terminals of the second power connector. 64. The bus power supply of claim 62, wherein the external power supply includes an AC power source for generating AC trunk line voltage. 65. The bus power supply of claim 61, wherein the sensing resistor comprises a variable resistor, and wherein the control circuitry is configured to: The variable resistance of the variable resistor is adjusted to adjust the amount of power that the bus power supply can deliver through the power bus during the on-time portion of the periodic time period. 66. The bus power supply of claim 65, further comprising: A power converter circuit, wherein the bus power supply has a power capacity that limits the maximum output power of the power converter circuit; and The control circuit is configured to adjust the variable resistance of the variable resistor to adjust the magnitude of the output power of the power converter circuit. 67. The bus power supply of claim 65, wherein the control circuitry is configured to adjust the variable resistance of the variable resistor to adjust the total power demand of the plurality of devices. 68. The load control system of claim 65, wherein the bus power supply is characterized by a nominal power capacity defined by a nominal power threshold, wherein the bus power supply is capable of supplying power to the plurality of devices indefinitely when the nominal power capacity is equal to or lower than the nominal power threshold; and The bus power supply is configured to adjust the variable resistance of the variable resistor to allow the plurality of devices to consume a power amount greater than the nominal power threshold on the power bus. 69. The load control system of claim 65, wherein the bus power supply is characterized by a nominal power capacity defined by a nominal power threshold, wherein the bus power supply is capable of supplying power to the plurality of devices indefinitely when the nominal power capacity is equal to or lower than the nominal power threshold; and The bus power supply is configured to adjust the variable resistance of the variable resistor such that the plurality of devices consume a power amount less than or equal to the nominal power threshold on the power bus. 70. The load control system of claim 61, wherein the bus power supply includes a current source, and the bus power supply is configured to conduct current to the power bus during the off-peak portion of the periodic time period to adjust the amount of power consumed by the plurality of devices. 71. The bus power supply of claim 61, wherein the bus power supply has a power capacity that defines a maximum amount of power that the bus power supply can deliver via the power bus; and The bus power supply is characterized by a nominal power capacity that defines a nominal power threshold, and the bus power supply is capable of supplying power to the plurality of devices indefinitely when the nominal power threshold is equal to or lower than the nominal power threshold, wherein the nominal power threshold is less than the maximum power amount defined by the power capacity of the bus power supply. 72. The load control system of claim 71, wherein the bus power supply is configured to supply power to the plurality of devices at one or more additional power capacities greater than the nominal power capacity for a period of time up to but not longer than a corresponding predetermined additional power period. 73. The bus power supply of claim 71, further comprising: An overpower protection circuit is configured to disconnect the bus voltage from the power bus in response to an overpower condition, wherein a first controllable switch circuit is coupled between the output of the overpower protection circuit and the power bus. 74. The bus power supply of claim 73, wherein the bus power supply is configured to continuously supply power to the power bus at a power level equal to or below the nominal power threshold without being interrupted or disconnected by the overpower protection circuitry of the bus power supply. 75. The load control system of claim 73, wherein the bus power supply includes a power converter circuit, wherein the overpower protection circuit is configured to disconnect the bus voltage from the power bus in response to the output power of the power converter circuit exceeding a first power increase threshold for a period of time exceeding a first power increase threshold, and is configured to disconnect the bus voltage from the power bus in response to the output power of the power converter circuit exceeding a second power increase threshold for a period of time exceeding a second power increase threshold. 76. A bus power supply for generating a bus voltage on a power bus for controlling multiple motorized curtains, the bus power supply comprising: A power converter circuit configured to generate a supply voltage; An overcurrent protection circuit is configured to receive the supply voltage from the power converter circuit and provide the bus voltage on the power bus. The overcurrent protection circuit is configured to: In response to the supply voltage exceeding a first power threshold for a first time period, the power converter circuit is disconnected from the power bus; and In response to the supply voltage exceeding a second power threshold for a second time period, the power converter circuit is disconnected from the power bus, wherein the first power threshold is less than the second power threshold, and the first time period is longer than the second time period. 77. The bus power supply of claim 76, wherein the overcurrent protection circuit is configured to de-energize the controllable conductive device to disconnect the power converter circuit from the power bus. 78. The bus power supply of claim 77, wherein the controllable conductive device comprises two field-effect transistors (FETs) in an anti-series configuration. 79. The bus power supply of claim 76, wherein the overcurrent protection circuit includes a first comparator and a second comparator, the first comparator being configured to compare a magnitude of the bus current with a first power threshold, and the second comparator being configured to compare the magnitude of the bus current with the second power threshold. 80. The bus power supply of claim 79, wherein the overcurrent protection circuit further includes a first timer and a second timer, the first timer being configured to determine whether the first time period has passed, and the second timer being configured to determine whether the second time period has passed. 81. The bus power supply of claim 79, wherein the overcurrent protection circuit includes a latch circuit configured to disconnect the power converter circuit from the power bus. 82. The bus power supply of claim 81, wherein the latching circuit is further configured to keep the power converter circuit disconnected from the power bus indefinitely. 83. The bus power supply of claim 76, wherein the overcurrent protection circuit is further configured to momentarily disconnect the power converter circuit from the power bus when the magnitude of the bus current exceeds a maximum power threshold. 84. The bus power supply of claim 83, wherein each motor drive unit comprises: A power connector configured to receive the bus voltage from the power bus; A power supply for a blackout curtain motor drive unit, the power supply for the blackout curtain motor drive unit being configured to conduct current from the power bus, conduct current from the internal energy storage element of the motor curtain, and generate a supply voltage; A load control circuit configured to receive the supply voltage and control the power delivered to the blackout curtain motor; and A control circuit configured to control the power supply of the blackout curtain motor drive unit to draw power from the power bus to charge the internal energy storage element or to power the movement of the electric curtain. 85. A load control system for controlling multiple motorized curtains, the load control system comprising: A bus power supply configured to generate a bus voltage on a power bus, the bus power supply including a power converter circuit and an overcurrent protection circuit, the power converter circuit being configured to generate a supply voltage, and the overcurrent protection circuit being configured to receive the supply voltage from the power converter circuit and provide the bus voltage on the power bus; and Multiple drive units for the plurality of motorized curtains, the drive units being coupled to the bus voltage to draw bus current from the power bus; The overcurrent protection circuit is configured to: Conducting the bus current drawn by the drive unit; Determine the magnitude of the bus current; The magnitude of the bus current is compared with a first current threshold. The magnitude of the bus current is compared with a second current threshold; and When the value of the bus current exceeds the first current threshold for a first time period, or when the value of the bus current exceeds the second current threshold for a second time period, the power converter circuit is disconnected from the power bus. 86. The load control system of claim 85, wherein the overcurrent protection circuit is configured to prevent the controllable conductive device from conducting to disconnect the power converter circuit from the power bus. 87. The load control system of claim 86, wherein the controllable conductive device comprises two field-effect transistors (FETs) in an anti-series configuration. 88. The load control system of claim 85, wherein the first current threshold is less than the second current threshold, and the first time period is longer than the second time period. 89. The load control system of claim 85, wherein the overcurrent protection circuit includes a first comparator and a second comparator, the first comparator being configured to compare the magnitude of the bus current with a first current threshold, and the second comparator being configured to compare the magnitude of the bus current with the second current threshold. 90. The load control system of claim 89, wherein the overcurrent protection circuit further comprises a first timer and a second timer, the first timer being configured to determine whether the first time period has passed, and the second timer being configured to determine whether the second time period has passed. 91. The load control system of claim 89, wherein the overcurrent protection circuit includes a latch circuit configured to disconnect the power converter circuit from the power bus. 92. The load control system of claim 91, wherein the latching circuit is further configured to keep the power converter circuit disconnected from the power bus indefinitely. 93. The load control system of claim 85, wherein the overcurrent protection circuit is further configured to momentarily disconnect the power converter circuit from the power bus when the magnitude of the bus current exceeds the instantaneous trip current. 94. The load control system of claim 85, wherein each motor drive unit comprises: A power connector configured to receive the bus voltage from the power bus; A power supply for a blackout curtain motor drive unit, the power supply for the blackout curtain motor drive unit being configured to conduct current from the power bus, conduct current from the internal energy storage element of the motor curtain, and generate a supply voltage; A load control circuit configured to receive the supply voltage and control the power delivered to the blackout curtain motor; and A control circuit configured to control the power supply of the blackout curtain motor drive unit to draw power from the power bus to charge the internal energy storage element or to power the movement of the electric curtain. 95. A bus power supply for supplying power to multiple electrical loads, the bus power supply comprising: A power converter circuit configured to generate a bus voltage for supplying power to the electrical loads, the plurality of electrical loads configured to conduct bus current from the power converter circuit; and Overcurrent protection circuit, the overcurrent protection circuit includes: A controllable switching circuit configured to conduct the bus current through the electrical load; A current monitoring circuit is configured to determine the magnitude of the bus current. A first threshold comparison and timing circuit is configured to compare the magnitude of the bus current with a first current threshold associated with a first power level, and adjust the magnitude of a current disable signal when the magnitude of the bus current exceeds the first current threshold for a first time period associated with the first power level. A second threshold comparison and timing circuit is configured to compare the magnitude of the bus current with a second current threshold associated with a second power level, and adjust the magnitude of the current disable signal when the magnitude of the bus current exceeds the second current threshold for a second time period associated with the second power level; and A latching circuit is configured to deactivate the controllable switching circuit to disconnect the power converter circuit from the electrical load in response to the magnitude of the current disable signal, and to maintain the controllable switching circuit deactivation independently of the magnitude of the current disable signal. 96. The bus power supply of claim 95, wherein the controllable switching circuit comprises two field-effect transistors (FETs) in an anti-series configuration. 97. The bus power supply of claim 95, wherein the first current threshold is less than the second current threshold, and the first time period is longer than the second time period. 98. The bus power supply of claim 95, wherein the first threshold comparison and timing circuitry includes a first comparator configured to compare the magnitude of the bus current with a first current threshold, and the second threshold comparison and timing circuitry includes a second comparator configured to compare the magnitude of the bus current with a second current threshold. 99. The bus power supply of claim 98, wherein the first threshold comparison and timing circuitry includes a first timer configured to determine whether the first time period has elapsed, and the second threshold comparison and timing circuitry includes a second timer configured to determine whether the second time period has elapsed. 100. The bus power supply of claim 95, wherein the latching circuit is further configured to keep the power converter circuit disconnected from the power bus indefinitely. 101. The bus power supply of claim 95, wherein the overcurrent protection circuit is further configured to momentarily disconnect the power converter circuit from the power bus when the magnitude of the bus current exceeds the instantaneous trip current. 102. A load control system for controlling multiple electrical loads, the load control system comprising: Multiple motorized blinds, each including a drive unit; and Bus power supply, the bus power supply comprising: A power converter circuit, configured to generate a bus voltage on a power bus; and An overcurrent protection circuit is configured to disconnect the power converter circuit from the power bus in response to the magnitude of the bus current of the power bus exceeding a first current threshold for a first time period or exceeding a second current threshold for a second time period. 103. The load control system of claim 102, wherein the overcurrent protection circuit is configured to prevent the controllable conductive device from conducting to disconnect the power converter circuit from the power bus. 104. The load control system of claim 103, wherein the controllable conductive device comprises two field-effect transistors (FETs) in an anti-series configuration. 105. The load control system of claim 102, wherein the first current threshold is less than the second current threshold, and the first time period is longer than the second current threshold. 106. The load control system of claim 102, wherein the overcurrent protection circuit includes a first comparator and a second comparator, the first comparator being configured to compare the bus current with a first current threshold, and the second comparator being configured to compare the bus current with the second current threshold. 107. The load control system of claim 106, wherein the overcurrent protection circuit further includes a first timer and a second timer, the first timer being configured to determine whether the first time period has passed, and the second timer being configured to determine whether the second time period has passed. 108. The load control system of claim 107, wherein the overcurrent protection circuit includes a latch circuit configured to disconnect the power converter circuit from the power bus. 109. The load control system of claim 102, wherein the overcurrent protection circuit is further configured to momentarily disconnect the power converter circuit from the power bus when the bus current exceeds the instantaneous trip current. 110. A system comprising: A bus power supply configured to generate a bus voltage on a power bus, the bus power supply comprising: A power converter circuit, configured to generate an output voltage; and Overcurrent protection circuit, the overcurrent protection circuit being configured to: Receive the output voltage from the power converter circuit; Conduct bus current to multiple electrical loads; Determine the magnitude of the bus current; The magnitude of the bus current is compared with a first current threshold associated with the first time period; The magnitude of the bus current is compared with a second current threshold associated with the second time period; Specifically, when the value of the bus current exceeds the first current threshold for the first time period or exceeds the second current threshold for the second time period, the overcurrent protection circuit is configured to disconnect the power converter circuit from the power bus. Multiple electrical loads are configured to receive the bus voltage and conduct current from the power bus. 111. The load control system of claim 110, wherein the plurality of electrical loads includes at least one peaked electrical load, the at least one peaked electrical load being configured to intermittently conduct current from the power bus, and wherein the current from the power bus conducted by the peaked load exceeds a high current threshold. 112. The load control system of claim 110, wherein the plurality of electrical loads comprises a plurality of blackout curtain motor drive units, each blackout curtain motor drive unit comprising: A power connector configured to receive the bus voltage from the power bus; A power supply for a blackout curtain motor drive unit, the power supply for the blackout curtain motor drive unit being configured to conduct current from the power bus, conduct current from the internal energy storage element of the motor curtain, and generate a supply voltage; A load control circuit configured to receive the supply voltage and control the power delivered to the blackout curtain motor; and A control circuit configured to control the power supply of the blackout curtain motor drive unit to draw power from the power bus to charge the internal energy storage element or to power the movement of the electric curtain. 113. The load control system of claim 110, wherein the overcurrent protection circuit is configured to prevent the controllable conductive device from conducting to disconnect the power converter circuit from the power bus. 114. The load control system of claim 113, wherein the controllable conductive device comprises two field-effect transistors (FETs) in an anti-series configuration. 115. The load control system of claim 110, wherein the first current threshold is less than the second current threshold, and the first time period is longer than the second time period. 116. The load control system of claim 110, wherein the overcurrent protection circuit includes a first comparator and a second comparator, the first comparator being configured to compare the magnitude of the bus current with a first current threshold, and the second comparator being configured to compare the monitored current with the second current threshold. 117. The load control system of claim 116, wherein the bus power supply further includes a first timer and a second timer, the first timer being configured to determine whether the first time period has elapsed, and the second timer being configured to determine whether the second time period has elapsed. 118. The load control system of claim 117, wherein the overcurrent protection circuit includes a latch circuit configured to disconnect the bus power supply from the power bus. 119. The load control system of claim 118, wherein the latching circuit is further configured to keep the power converter circuit disconnected from the power bus indefinitely. 120. The load control system of claim 110, wherein the overcurrent protection circuit is further configured to momentarily disconnect the power converter circuit from the power bus when the magnitude of the bus current exceeds the instantaneous trip current. 121. A bus power supply for providing a bus voltage to a plurality of devices, the bus power supply comprising: A power converter configured to generate the bus voltage on the power bus during the on-phase of a periodic time period and configured not to generate the bus voltage on the power bus during the off-phase of the periodic time period. Control circuit, the control circuit being configured to: Determine the total requested power during the off-peak portion of the periodic time period; and The variable resistance of the variable resistor of the bus power supply is adjusted based on the total requested power and one or more power thresholds to ensure that the power converter maintains an output power that does not exceed the threshold for a predetermined amount of time. 122. The power distribution system of claim 1, wherein the bus power supply includes the control circuit. 123. A bus power supply configured to generate a DC bus voltage on a DC power bus, the bus power supply comprising: A power converter circuit, configured to generate an output voltage; and Overcurrent protection circuit, the overcurrent protection circuit includes: The first amplifier, configured to: Receive the output voltage from the power converter circuit; and A current monitoring voltage signal with a certain value is generated, the value indicating the value of the monitored current, wherein the monitored current is the current conducted from the power converter circuit through the overcurrent protection circuit; The first comparator is configured to: Receive the current monitoring voltage signal; The current monitoring voltage signal is compared with a first threshold; and When the current monitoring voltage signal is greater than the first threshold, a first threshold signal is generated; A first timer, wherein the first timer is configured to monitor the first threshold signal for a first time period, and generate a disable signal when the first timer receives the first threshold signal for the duration of the first time period; The second comparator is configured to: Receive the current monitoring voltage signal; The current monitoring voltage signal is compared with a second threshold; and If the current monitoring voltage signal is greater than the second threshold, a second threshold signal is generated; A second timer, wherein the second timer is configured to monitor the second threshold signal for a second time period, and generate the disable signal when the second timer receives the second threshold signal for the duration of the second time period; A latching circuit, configured to receive the disable signal and output a latching signal in response to the disable signal; and A controllable switching circuit is configured to connect or disconnect the power converter circuit from the DC power bus in response to the latch signal. 124. A system comprising: The bus power supply as described in claim 123; and Multiple drive units, wherein each drive unit includes: A power connector configured to receive the DC bus voltage from the DC power bus; A drive unit power supply, configured to conduct current from the DC power bus, conduct current from internal energy storage elements, and generate a supply voltage; A load control circuit configured to receive the supply voltage and control the power delivered to the electrical load; and A control circuit configured to control the drive unit power supply to draw power from the DC power bus.