DE102019112006B4 - CONTROL CIRCUIT AND TECHNIQUES FOR CONTROLLING AN LED ARRAY - Google Patents

Abstract

Light emitting diode (LED) array control circuit, the control circuit (110; 210; 310; 400) comprising:
a plurality of output terminals (OUTO - OUT-N), wherein each of the plurality of output terminals (OUTO - OUT-N) is designed to control a respective LED string of an LED array (160; 260);
a plurality of current measuring circuits (216-0, 216-N), each configured to determine a current intensity for a respective output terminal (216-0, 216-N);
several switches (M ₀ , M _N ),
a plurality of driver circuits (212-0; 212-N) having a plurality of current limiting circuits (214-0, 214-N); and
a plurality of temperature sensors (420), each associated with one of the plurality of switches (M ₀ , M _N ), wherein:
each of the plurality of switches (M ₀ , M _N ) is adapted to control the current intensity for a respective output terminal (OUTO - OUT-N) and to operate independently of each other of the switches (M ₀ , M _N ), wherein:
each of the plurality of driver circuits (212-0; 212-N) is configured to actuate a respective switch (M ₀ , M _N ) of the plurality of switches,
each of the plurality of current limiting circuits (214-0, 214-N) is associated with a respective switch (M ₀ , M _N ) of the plurality of switches (M ₀ , M _N ), and
each of the plurality of current limiting circuits (214-0, 214-N) is configured to adjust the operation of the respective switch (M ₀ , M _N ) associated with the respective current limiting circuit (214-0, 214-N) to limit the current for each respective output terminal (OUTO - OUT-N), and
wherein each of the plurality of temperature sensors (420) is configured to compare a temperature of the switch (M ₀ , M _N ) associated therewith with a temperature threshold and, in response to the detected temperature exceeding the temperature threshold, to turn off the switch or change a duty cycle of the switch.

Description

This disclosure relates to LED control circuits.

Light-emitting diode (LED) arrays can be used to provide lighting in a variety of applications, such as automotive, indoor living and work spaces, outdoor lighting, and similar applications. An LED array may also be referred to as an LED matrix. Some examples of LED lighting systems include features such as individual control of multiple LEDs, which may include dimming and changing colors to respond to a desired lighting output.

This disclosure is generally directed to devices and techniques for individually controlling multiple light emitting diodes (LEDs) in an LED array. An LED array may include multiple strings of LEDs, where each string may include a single LED or multiple LEDs. The techniques of this disclosure include a parallel approach to controlling an LED array with a current sensing circuit for each LED string. The current sensing circuits for each LED string may be selectable by a controller via a multiplexer (MUX). The arrangement of switching elements in the techniques of this disclosure provide an initialization phase and an operating phase for the LED array, which may have advantages over other examples of LED array control circuits. For example, the techniques of this disclosure may achieve an accurate and substantially equal current across all LEDs to ensure homogeneous light output, and may adjust the current to compensate for device process and manufacturing variability as well as changes in operating conditions. An LED control circuit of this disclosure may include system safety features including temperature sensing and overvoltage and overcurrent sensing and protection.

The US 2007 / 0 195 025 A1 describes a control circuit for controlling several LED strings, each LED string being connected in series to a transistor which is controlled by a current limiter in order to set the current through the respective LED string to a predetermined value.

One embodiment of the invention relates to an LED array control circuit according to claim 1. Further embodiments relate to a method according to claim 9 and a system according to claim 12.

• 1 ist ein Blockschaltbild, das einen Überblick über ein Beispielsystem zum Steuern eines Leuchtdioden-(LED)-Arrays gemäß einer oder mehr Techniken dieser Offenbarung veranschaulicht.
• 2 ist ein Blockschaltbild, das ein Beispielsystem zum Steuern eines LED-Arrays, das einen integrierten Mehrkanal-High-Side-Schalter mit digitaler Kommunikationsschaltung enthält, veranschaulicht.
• 3 ist ein Blockschaltbild, das ein Beispielsystem zum Steuern eines LED-Arrays, das einen integrierten Mehrkanal-High-Side-Schalter, der über einzelne Eingangspins für jeden LED-Strang angesteuert wird, enthält, veranschaulicht.
• 4 ist ein Blockschaltbild, das eine integrierte Beispiel-Mehrkanal-High-Side-Schalter-Schaltung mit digitaler Kommunikationsschaltung veranschaulicht.
• 5 ist ein Blockschaltbild, das eine integrierte Mehrkanal-High-Side-Schalter-Schaltung, die über einzelne Eingangspins für jeden LED-Strang angesteuert wird, veranschaulicht.
• 6 ist ein Flussdiagramm, das eine Beispiel-Technik für eine Initialisierungsphase eines Systems zum Steuern eines LED-Arrays gemäß einer oder mehr Techniken dieser Offenbarung veranschaulicht.
• 7 ist ein Flussdiagramm, das eine Beispiel-Technik für eine Betriebsphase eines Systems zum Steuern eines LED-Arrays gemäß einer oder mehr Techniken dieser Offenbarung veranschaulicht.

The details of one or more examples of the disclosure are set forth in the accompanying drawings and description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings and from the claims.

• 1 is a block diagram illustrating an overview of an example system for controlling a light emitting diode (LED) array in accordance with one or more techniques of this disclosure.
• 2 is a block diagram illustrating an example system for controlling an LED array that includes an integrated multi-channel high-side switch with digital communication circuitry.
• 3 is a block diagram illustrating an example system for controlling an LED array that includes an integrated multi-channel high-side switch controlled by individual input pins for each LED string.
• 4 is a block diagram illustrating an example multi-channel high-side switch integrated circuit with digital communication circuitry.
• 5 is a block diagram illustrating a multi-channel high-side switch integrated circuit controlled by individual input pins for each LED string.
• 6 is a flowchart illustrating an example technique for an initialization phase of a system for controlling an LED array according to one or more techniques of this disclosure.
• 7 is a flowchart illustrating an example technique for a phase of operation of a system for controlling an LED array in accordance with one or more techniques of this disclosure.

This disclosure is directed to devices and methods for individually controlling multiple light emitting diodes (LEDs) in an LED array. An LED array may include multiple strings of LEDs, each string including a single LED or multiple LEDs. The techniques of this disclosure include a parallel approach to controlling an LED array with a current sensing circuit for each LED string. An LED string may also be referred to as an LED branch. The current sensing circuits for each LED string may be selectable with a controller via a multiplexer (MUX). A controller may include a processor circuit such as a microprocessor or a microcontroller (µC).

The arrangement of circuit elements in the techniques of this disclosure provides an initialization phase and an operating phase for the LED array, which may have advantages over other examples of LED array control circuits. For example, the techniques of this disclosure may achieve accurate and substantially equal current across all LEDs to ensure homogeneous light output. The LED array control circuit of this disclosure may address various challenges in LED array control. For example, because LED arrays may be subject to process and manufacturing variability, paralleling the LEDs of the LED array and simply connecting them to a common voltage source may result in unequal current in the parallel branches and inhomogeneous light output. Additionally, LED arrays may operate under varying conditions, such as temperature changes.

In contrast, the techniques of this disclosure may provide advantages over other LED control circuit examples, such as improved current readback for each LED string, as well as system protection in the event of component failure or other problems. A current sensing circuit is included for each channel of the LED array control circuit that controls an LED string. The current sensing circuit output may be sent to a controller via a MUX, which may reduce the complexity and duration of the initialization phase compared to other examples. Additionally, the current sensing circuit allows for continuous checking of activated LEDs, enabling much better diagnostic coverage and system protection (e.g., against short circuits), as well as compensation for temperature effects on the LEDs. In some examples, the LED control circuit of this disclosure may detect temperature effects by repeatedly reading the current per branch. The LED control circuit may adjust the supply voltage and/or the duty cycle of the switches that control the current to each LED string. In some examples, the LED control circuit may also include a temperature sensor for the switches that control the LED array. An LED control circuit may also be referred to as an LED array control circuit.

1 is a block diagram illustrating an overview of an example system for controlling an LED array in accordance with one or more techniques of this disclosure. The system 100 may include a processing circuit 120 in communication with an LED array control circuit 110 as well as a power supply 130.

The LED array control circuit 110 may be adaptable to a variety of LED control applications. For example, the LED array control circuit 110 may include both an input for digital communication with the processing circuit 120 and inputs for direct control of the LED array by the processing circuit 120 via a communication path 122. The LED array control circuit 110 may include N outputs (OUTO - OUT-N) for controlling up to N LED arrays 160. Each LED string in the LED array 160 may include one or more LEDs. In some examples, a single output, such as OUT3, may drive a single LED string. In other examples, multiple LED outputs may be used to drive a single LED string. For example, OUT6 may be shorted to OUT5, which may provide additional current to a particular LED string. In other examples, an output of the LED array control circuit 110 may not be connected to any LEDs. In this disclosure, an LED string may also be referred to as an LED row or LED branch of the LED array 160. Each respective output terminal OUTO - OUT-N and switch M0 - MN of the LED control circuit 110 may be referred to as a channel. For example, channel 0 may include switch M0 and output terminal OUTO and drive an LED string of the LED array 160.

The circuit for each output terminal OUTO - OUT-N of the LED array control circuit 110 may include a switch configured to control the current intensity for each respective output terminal and independent of any other respective switch (in 1 not shown). In some examples, the respective switches may control the current using pulse width modulation (PWM), and therefore the current to an LED string of the LED array 160 may be described as an average current.

Each output port may also include a current sensing element to individually sense the current for each respective output channel. The current sensing element in each LED branch may be coupled by the processing circuit 120 via a multiplexer (in 1 not shown). The processing circuit 120 can determine the respective current intensity for each LED string of the LED array 160 by selecting the current measuring element for that branch via the communication path 122. The current measuring element can also be referred to as a current sensor. The LED array control circuit 110 can also contain a current limiting circuit for each of the output terminals OUTO - OUT-N (in 1 not shown).

The LED control circuit 110 may also include one or more temperature sensing elements (in 1 not shown). In some examples, LED array control circuit 110 may include a separate temperature sensor associated with each respective output port. In other examples, LED array control circuit 110 may include a single temperature sensor for all output ports or temperature sensors for a group of outputs. For example, OUT0 - OUT2 may be associated with a first temperature sensor, while OUT3 - OUT5 may be associated with a second temperature sensor.

The processing circuit 120 may communicate with both the LED array control circuit 110 and the power supply 130 to send and receive signals that may include both data and commands. In some examples, the processing circuit 120 may also receive signals from external sources such as a temperature sensor that may provide outside air temperature or other types of sensors. Examples of the processing circuit 120 may include any type of processor circuit including one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a system on a chip (SoC), or an equivalent discrete or integrated logic circuit. A processor may be an integrated circuit, i.e., an integrated processing circuit, and this integrated processing circuit may be implemented as a fixed hardware processing circuit, a programmable processing circuit, and a combination of both a fixed and a programmable processing circuit. In the example of a vehicle, processing circuitry 120 may be an engine control unit (ECU), or it may be in signal communication with an ECU or other processors in the vehicle, such as a computer or a single integrated circuit containing a processor core, memory, and programmable input/output peripherals.

The power supply 130 may provide electrical power to drive the LED strings of the LED array 160 in response to commands from the processing circuit 120. Commands from the processing circuit 120 may cause the power supply 130 to adjust the voltage level and/or current from the power supply 130 to the VS terminal to power the LED strings. The operating voltage to the VS terminal may also be referred to as the supply voltage. In some examples, the power supply 130 may also provide power to support the operation of the LED array control circuit 110 and the processing circuit 120. For example, the power supply 130 may provide power to the digital circuits included in the processing circuit 120 and the LED array control circuit 110 (e.g., VDD). In other examples, support power for the processing circuit 120 and the LED array control circuit 110 may be provided from a separate power supply in the system 100 (in 1 not shown).

In some examples, power supply 130 may be considered a voltage regulator. In other examples, power supply 130 may include a voltage mode DC-DC converter configured to output voltages based on commands from processing circuitry 120. In other examples, power supply 130 may include a linear regulator, a switched mode power supply (SMPS), or other types of power supplies that can provide a regulated output to LED array control circuitry 110.

The system 100 with the LED array control circuit 110 can be used in applications such as controlling an LED array to turn on, turn off, dim when a given event occurs. In the example of a vehicle, the processing circuit 120 can receive a signal that a turn signal indicator is flashing. The processing circuit 120 can cause the LED array control circuit 110 to dim or turn off an LED array near the turn signal indicator to make the turn signal more visible. The processing circuit 120 can cause the LED array control circuit 110 to adjust the brightness of a headlight or interior light of a vehicle in response to a light sensor indicating sunrise, sunset, or entering a tunnel. In some examples, the LED array control circuit 110 may be used as an adaptive front beam for vehicles, such as automobiles or motorcycles. In an alternate example of using the circuit within a building, the processing circuit 120 may receive an indication from a motion sensor or other type of sensor, and the processing circuit 120 may cause the LED array control circuit 110 to activate or deactivate one or more strands of the LED array 160 in response to the indication.

In other examples, processing circuitry 120 may dim one or more strings of an LED array by reducing the average current to the LED string, e.g., by causing LED array control circuitry 110 to change the PWM scheme. LED array control circuitry 110 may also control the overall brightness of LED array 160 by either changing the PWM scheme of some of the LED strings while not changing the PWM scheme of other LED strings. Similarly, to control overall brightness, LED array control circuitry 110 may turn off one or more LED strings while leaving other LED strings on.

In other examples, the LED array control circuit 110 may change the output color of the LED array 160 by individually controlling the brightness of one or more LED strings of the LED array 160. For example, the LED string connected to OUT0 may be a first color, e.g., red, while the LED string connected to OUT3 may be a second color, e.g., blue.

In operation, the LED array control circuit 110 may have advantages over other types of LED control circuits. According to one example, the current sensing element in each LED branch, which may be selectable by the processing circuit 120 via a multiplexer, may provide advantages during an initialization phase as well as during an operation phase. For example, the initialization phase may be less complex compared to other types of LED control circuits. In addition, the duration of the initialization phase may be tuned depending on the application and requirements, e.g., fast start-up, minimal power consumption, or other parameters.

In one example, the power supply 130 may be configured to start with a voltage low enough to ensure a current that is safely below the maximum ratings of the LEDs in the LED array 160, then ramp the voltage up at a predetermined voltage slew rate. In the example of several white LEDs, the initial voltage may be approximately 2.5 V. During the ramp-up, the LED array control circuit 110 may measure the current in each LED string and output the current measurement to the processing circuit 120. Several or all of the LED strings may be activated simultaneously. In some examples, the voltage ramp-up portion of the initialization phase may stop when all legs have reached at least a predetermined target current. The voltage may therefore be defined by the output voltage of the output terminal having the LED string with the highest forward voltage. The predetermined target current may be set based on the application, e.g. B. interior lighting, headlight or a similar application that may include the types and number of LEDs in the LED array 160.

The LED array control circuit 110 may be configured to individually control a duty cycle of the PWM scheme for each of the respective switches for each output terminal OUTO - OUT-N such that an average current on all LED branches is approximately the same current. In some examples, the LED array control circuit 110 may receive instructions to individually adjust the duty cycle for each output terminal, e.g., via digital messages on the communication path 122. In other examples, the processing circuit 120 may directly control a control circuit associated with each respective switch and output terminal to control the PWM scheme.

During an operating phase, the LED array control circuit 110 may continuously test the active LED strings of the LED array 160, which may enable improved diagnostic detection and system protection (e.g., against short circuits). Similarly, individual control of the LED string allows compensation for temperature effects of the LEDs, which is desirable in some applications. As the temperature changes, the behavior of an LED may change, and therefore it may be necessary to adjust the voltage output by the power supply 130 and/or the duty cycle of the PWM scheme to compensate for the change in behavior. The temperature effects may be determined by repeatedly reading the current (average current) in each respective LED branch so that the processing circuit 120 may adjust the supply voltage and/or the duty cycle of the switches. In some examples, functions within the LED array control circuit 110 may also be configured to adjust the duty cycle of the switches to adjust the current.

In some examples, the LED array control circuit 110 may include a variable or fixed resistor in each branch/output terminal to further control the current balance between the LED branches. A variable resistor may be an example technique to reduce the current spikes in the LED string with the lowest forward voltage.

Because the LED array control circuit of this disclosure includes current measurement in each LED branch and a multiplexer for outputting information, the LED array control circuit of this disclosure may have improved functionality and advantages compared to other types of LED control circuits. For example, one possible way to control individual LEDs, including dimming, is to put the LEDs in a chain and short each LED with a switch to make each one individually controllable. Individual switches on a single chain may have the disadvantage of less control over the voltage and current on the individual chain. Another way to control individual LEDs is to connect LEDs in parallel and control each path with switches or linear current sources. Some examples using the parallel approach with current sources for each LED chain in combination with a voltage source may have low efficiency due to power losses in the current sources.

Other examples of the parallel approach may include examples that include a voltage source and switches with a single current sensing element for the entire LED array. A single current sensing element may require complex initialization of the LED array system such as initializing a first string, then shutting down the first string before initializing a second string, and so on. Additionally, a single current sensing element provides limited diagnostics during operation, such as system diagnostics, and the system may have a slow response time in the event of a short circuit in one of the LED strings. The limited diagnostics may also result in a forward voltage shift that affects the current at a particular voltage due to a temperature change of LEDs caused by activation or the environment. Some examples of LED control systems with limited diagnostics may not be able to monitor current or temperature during operation, but only during initialization.

In contrast, the LED array control circuit 110 may provide a less complex and customizable initialization phase according to one or more techniques of this disclosure. Additionally, during the operation phase, the LED array control circuit 110 may provide continuous testing of active LEDs, better diagnostic sensing, and system protection against short circuits and overvoltage, as well as compensation for temperature effects of the LEDs. In the case of a short circuit or high average current on an LED string, the current limiter may become active and protect the system, for example, either by shutting it down or by reducing the average current. In the case of an open load (e.g., an LED that is damaged or destroyed), the current is almost zero, so the individual current measurement for the LED string may detect the failure, enabling the system to report the short circuit and respond accordingly. Some example responses may be to issue an alarm or an alert, adjust the current or voltage to compensate for the short circuit, or similar responses. Therefore, a current limiter of this disclosure is different from limiting current, for example with a resistor.

In some examples, heating of an individual LED or LED string may be detected by comparing the current and voltage at the regulator to the most recent current and voltage. As an LED heats at a constant current, the LED forward voltage may decrease. Similarly, as the temperature increases at a constant forward voltage, the LED current may also increase. By measuring an increased current (compared to the initial value), a temperature change may be detected, e.g., by processing circuitry 120.

2 is a block diagram illustrating an example system for controlling an LED array that includes an integrated multi-channel high-side switch with digital communication circuitry. The system 200 includes more detailed examples of LED array control circuitry, power supply, and processor circuitry similar to the LED array control circuitry 110, power supply 130, and processing circuitry 120 described with respect to 1 and, unless otherwise stated, have the same features and benefits.

The system 200 may include a microcontroller (µC) 220 in communication with an LED array control circuit 210 as well as a voltage regulator 230. As with the system 100, the system 200 may provide individual control of multiple LED strings in the LED array 260, including dimming. The system 200 may achieve an accurate and equal current across all LEDs, which may ensure a homogeneous light output. Individual control of the current in each LED string compensates for a deviation in the forward voltage of the LEDs, which may be subject to manufacturing variation as well as temperature dependence. The techniques included in the system 200 may also compensate for overshoots of the current and/or voltage during load changes and improve current accuracy compared to other types of LED control circuits. System 200 follows the parallel approach described above for system 100 and provides current readback for each LED as well as system protection.

The microcontroller 220 may include an analog-to-digital converter (ADC) input 222, a digital input/output (I/O) 224, a power and communication connection 226 to the voltage regulator 230, and other connections such as VIN, ground (VSS), or other 2 connections not shown. Some other connections may include data communication with other parts of a larger system such as an ECU, a user interface, outputs to alarms or indications, and similar connections. As with the above with respect to 1 described processor circuit 120, the microcontroller 220 is merely an example of a type of processor circuit that may be used to communicate with and control the LED array control circuit 210. In some examples, the microcontroller 220 may communicate with the LED array control circuit 210 via the digital I/O 224 and omit the ADC 222 or leave the ADC 222 unconnected.

As with the one relating to 1 described power supply 130, the voltage regulator 230 may adjust one or more output voltages or currents in response to commands from the microcontroller 220. For example, during an initialization phase, the voltage regulator 230 may output an operating voltage to the VS input terminal of the LED array control circuit 210 as commanded by the microcontroller 220 in response to the microcontroller 220 determining the LED string with the highest voltage level. The operating voltage at the VS terminal may also be referred to as a supply voltage. In some examples, the voltage regulator 230 may supply the VIN to the microcontroller 220. In other examples, VIN for the microcontroller 220 may be determined by another, in 2 power supply, not shown. The voltage regulator 230 may also be referred to as a voltage supply circuit.

The LED array control circuit 210 may be configured to drive the LED strings of the LED array 260 to maintain approximately equal current in each string and to provide protection against over-temperature, over-voltage and over-current. The LED array control circuit 210 may include multiple outputs OUTO - OUT-N and circuitry associated with each output OUTO - OUT-N such as current sensing circuits 216-0 - 216-N, multiple switches M0 - MN, driver circuits 212-0 - 212-N and current limiting circuits 214-0 - 214-N. The LED array control circuit 210 may also include a digital communication circuit 215 and a MUX output 240. In some examples, the components of the LED array control circuit 210 may be integrated into a single integrated circuit. In the example of 2 The output terminal OUTO is connected to a three-LED string of the LED array 260. The output terminal OUT-N is connected to an LED string with a single LED.

The driver circuits 212-0 - 212-N (collectively, driver circuits 212) may be configured to actuate a respective one of the switches M0 - MN that control the current to each LED string in the LED array 260. For example, in examples where the switches M0 - MN are metal oxide field effect transistors (MOSFETs) or a similar type of switch with a gate terminal, a respective driver circuit may drive the gate of the respective switch. Although the current sensing circuits 216-0 - 216-N (collectively, current sensing circuits 216) and the current limiting circuits 214-0 - 214-N (collectively, current limiting circuits 214) in 2 shown as separate blocks, in some examples, the driver circuits 212 may include current sensing circuits 216 and current limiting circuits 214. The current sensing circuits 216 may also be referred to as current sensing circuits 216. The current limiting circuits 214 may offer advantages over limiting current in a respective channel through other techniques, such as simply adding a resistor to each channel. For example, a resistor would dissipate energy throughout the circuit operation and therefore may be less efficient than the current limiting circuits 214 of this disclosure. Other advantages may include the ability to limit the current to a predefined value. The current limiting circuits 214 would maintain the current limit as the voltage changes. A resistor would only limit to a fixed current when the voltage is not changed. Depending on the application, in some examples, one or more branches of the LED array control circuit 210, in addition to the current limiting circuits 214 as described above with respect to 1 described, a variable resistor must be added.

In some examples, the driver circuits 212, as indicated by the digital communication tion circuit 215 may output a PWM scheme. For example, after the initialization phase, microcontroller 220 may determine the operating point (output voltage and current) for output terminal OUTO and calculate a first PWM scheme with a first duty cycle. Digital communication circuit 215 may receive a signal from microcontroller 220 to set driver circuit 212-0 to cause switch M0 to operate at the first duty cycle. Thereafter, unless reprogrammed, driver circuit 212-0 may output the first PWM scheme with the first duty cycle. In other examples, driver circuit 212-0 may only output a PWM scheme with a given duty cycle under direct, continuous control of digital communication circuit 215.

Each switch M0 - MN can be designed to control the current for each respective output terminal. In the example of 2 switch M0 connects the VS terminal of the LED array control circuit 210 to the output terminal OUTO. The driver circuit 212-0 may send a PWM signal to the gate of switch M0, which controls the average current delivered to the output terminal OUTO. The remaining switches connect the VS terminal of the LED array control circuit 210 to the respective output terminal and control the current to each output terminal in a similar manner. Each switch M0-MN may be configured to operate independently of any other respective switch of the plurality of switches. The VS terminal of the LED array control circuit 210 receives power (voltage and current) from the power supply, voltage regulator 230.

Each of the driver circuits 212 may include an associated current limiting circuit for each output terminal OUTO - OUTN and switches M0 - MN. Each respective current limiting circuit of the current limiting circuits 214 may be configured to limit the current for each respective output terminal OUTO - OUTN to a respective predetermined current limit. Each respective predetermined current limit set for one current limiting circuit is independent of any other respective predetermined current limit set for another current limiting circuit. For example, the predetermined current limit for the current limiting circuit 214-0 may be different from the predetermined current limit for the current limiting circuit 214-5 (in 2 not shown). In some examples, the current limiting circuits 214 do not change the duty cycle. The duty cycle may be adjusted to achieve a predetermined average current. The current limiting circuits 214 may protect the LEDs from damage, ie, to ensure that the LED specific maximum current is not reached.

An IC including the LED array control circuit of this disclosure may be configured by a user to operate differently depending on a particular application. For example, in an application with digital communication capability, the digital communication circuit 215 may be configured to program or set the respective current limit for a respective current limiting circuit. During operation, the current limiting circuit may operate independently to limit the current associated with a respective output terminal and switch, i.e., without further input from the digital communication circuit 215 or the microcontroller 220. For example, the digital communication circuit 215 may program the current limiting circuit 214-0 to a predetermined limit of 120 mA. The current limiting circuit 214-0 may then monitor the current through the switch M0, e.g., via the current sensing circuit 216-0, and adjust the PWM scheme of the driver 212-0 to reduce the average current to the output terminal OUTO as required. In some examples, a current limiting circuit 214 may limit the current by triggering one or more driver circuits 212 to turn off the respective switch associated with the driver circuit.

In other examples, digital communication circuit 215 may monitor the current through switch M0, e.g., via current sensing circuit 216-0, and directly control current limiting circuit 214 to reduce the average current to output terminal OUTO as needed. In other examples, digital communication circuit 215 may communicate via digital I/O path 228 and receive commands from microcontroller 220 to cause current limiting circuit 214-0 and driver 212-0 to reduce the current to output terminal OUTO when the current through switch N0 approaches or exceeds the predetermined current threshold. Similarly, microcontroller 220 may control the current to each output terminal, e.g., via current sensing circuit 216-0. B. via the current sensing circuits 216 and the load current sensing MUX output port 240, and can directly control the PWM scheme of the associated driver circuit with a current approaching or exceeding the predetermined threshold, or send commands to the digital communication circuit 215 to control this.

In other examples, the microcontroller 220 may provide the LED array control circuit 210 with a target value for an average output current and a maximum output current. To achieve this average current, the LED control circuit 210 may internally determine a PWM scheme and monitor the current with the current sensing circuits 216. The LED array control circuit 210 may also internally set the current limiting circuits 214 to the maximum output current value provided by the microcontroller 220. In other examples, the LED array control circuit 210 may determine that the set average current in the LED(s) cannot be achieved and report directly back to the microcontroller 220 that the output voltage from the voltage regulator 230 should be increased. In other examples, the LED array control circuit 210 may determine that the voltage from the voltage regulator 230 is too high (e.g., from a low duty cycle on all LED strings or because of the set current limit). The LED array control circuit 210 may directly feedback to the microcontroller 220 that the output voltage from the voltage regulator 230 should be reduced.

In some examples, digital communication circuitry 215 may operate over digital I/O path 228 using a serial peripheral interface (SPI) bus. SPI is a specification for a synchronous serial communication interface used for short-range communication, primarily in embedded systems. The SPI bus specifies four logic signals: SCLK: serial clock (outside a master), MOSI: master output, slave input or master out, slave in (data output from master), MISO: master input, slave output or master in, slave out (data output from slave), and SS: slave select (which may be active-low, output from master). In other examples, alternate pin naming conventions may be used. In some examples, SPI may be a so-called four-wire serial bus, as opposed to three-, two-, and one-wire serial buses. The SPI can be described as a synchronous serial interface, but it is different from the Synchronous Serial Interface (SSI) protocol, which is also a four-wire serial synchronous communication protocol. The SSI protocol employs differential signaling and provides only a single simplex communication channel. In other examples, the digital communication circuit 215 may use other standard interface protocols, or a custom protocol.

The default threshold for each output terminal OUTO - OUT-N can be set by a user based on the application. For example, the LED array control circuit 210 can drive an LED array, e.g., the LED array 260, with a variety of LEDs having different maximum current limits. In an automotive application, the LED array 260, along with other LED strings, can include one or more strings of LEDs for running lights, one or more strings for low beam, and additional strings for high beam headlights. The running light LEDs can have a different maximum current limit than the LEDs used for the headlights. Therefore, the default current limit associated with the running light output terminals can be different from the default current limit associated with the headlight output terminals.

The voltage regulator 230 and the microcontroller 220 may control the LED array 260 as described above with respect to 1 described, with an initialization phase. That is, the microcontroller 220 may configure the voltage regulator 230 to start with a voltage low enough to ensure that the current is below the maximum ratings of the LEDs in the LED array 260, then ramp the voltage up at a predetermined voltage slew rate. The voltage ramp portion of the initialization phase may stop when all branches have reached at least a predetermined target current. Similar to the predetermined current limit described for the current limit circuits 214, a user may set the predetermined target current for each output terminal OUTO - OUTN connected to each leg of the LED array 260. In some examples, the microcontroller 220 may be programmed with the predetermined target current. In other examples, the communication circuit 215 or the driver circuits 212 may be configured with the predetermined target current.

The system 200 may switch from the initialization phase to the operating phase, such as when all of the LED strings of the LED array 260 have reached the target current. The LED array control circuit 210 may then adjust the operating current as needed to compensate for temperature changes, heating effects of current through the switches and LED strings, changes in commands from other systems outside the system 200, such as a command to turn on the headlights when entering a darkened tunnel.

3 is a block diagram illustrating an example system for controlling an LED array that includes an integrated multi-channel high-side switch driven via individual input pins for each LED string. In some examples, an IC with an LED array control circuit, such as LED array control circuit 210 or LED array control circuit 310, may include both a digital communication interface and individual input pins for each LED string. Depending on the application, either interface may be used. For example, in a system without digital communication capability, as shown in system 300, an LED array control circuit may communicate with the processing circuitry via the individual input pins for each LED string, and each digital interface may remain unconnected.

As with the above with regard to 2 System 200 described above, system 300 includes more detailed examples of LED array control circuitry, power supply and processor circuitry similar to that described with respect to 1 described system 100. Unless otherwise stated, the LED array control circuit 310 has the same functions and advantages as the LED array control circuit 210 and the LED array control circuit 110. For example, the driver circuits 212, the current limiting circuits 214, the current sensing circuits 216, the switches M0 - MN and the output terminals OUTO - OUT-N function as described above with respect to 2 Similarly, the LED array 260, the voltage regulator 230 and the load current sense MUX output port 240 function as described above with respect to 2 System 300 includes similar connections to power and ground as System 200, such as V _IN , VS , and VSS .

The LED array control circuit 310 may receive a PWM scheme from I/O 324 for each respective output terminal OUTO - OUT-N. Each input terminal In ₀ - In- _N may receive a separate PWM scheme that controls the current in each channel via the driver circuits 212 and switches M0 - MN. Each PWM scheme for each channel may be independent of the PWM scheme for any other channel.

The LED array control circuit 310 may output the sensed current for each respective channel to the ADC port 322 of the microcontroller 320 via the load sense MUX output port 240. The microcontroller 320 may cycle through the active channels or all of the channels of the LED array control circuit 310 to periodically determine the current for each channel associated with each output port OUTO - OUT-N. In some examples, the microcontroller 320 may determine which channel to monitor by sending a signal to the interface 315 via the select pin DSEL. In other words, the MUX circuit of the LED array control circuit 310 may be configured to receive information from each driver circuit 212-0 - 212-N, output the information at the load current sense port 240 in response to the signal received at DSEL. The information output at the sense terminal 240 includes a respective current magnitude (e.g., average current) for a respective output terminal OUTO - OUT-N. As described above, the current sense circuits 216 may be separate or integrated into the driver circuits 212.

In some examples, the microcontroller 320 may monitor each of the current sensing circuits 216 and adjust the PWM scheme to limit the current of a channel that may be approaching or exceeding the predetermined current limit. In other examples, the LED array control circuit 310 may control the duty cycle of the PWM scheme to limit the output current to the LED strings. In other examples, the microcontroller 320 may individually set a current limit for each of the current limiting circuits 214, which may then operate to limit the current for each channel without further input from the microcontroller 320. In other examples, the current limiting circuit 214-0 - 214-N may be preprogrammed with a separate, predetermined current limit for each channel. For example, during manufacturing assembly, such as during circuit test, a programming function may pre-program each current limit circuit of the current limit circuits 214 depending on the expected application. After being assembled into a final product, the LED array control circuit 310 may maintain these current limits during operation.

4 is a block diagram illustrating an example integrated multi-channel high-side switch circuit with digital communication circuitry. The LED array control circuit 400 of 4 shows additional details of an example LED array control circuit such as the LED array control circuit 210 and the LED array control circuit 310 shown in the 2 and 3 The LED array control circuit 400 includes a digital communication circuit 415, which is similar to the LED array control circuit 210. However, an IC may be provided with an LED array control circuit such as the LED array control circuit 400 as described above with respect to the 1 and 3 described both a digital communication interface 415 and individual input pins 405 for each LED string.

Similar to the above with regard to the 2 and 3 In addition to the LED array control circuits 210 and 310 described above, the LED array control circuit 400 includes switches M0 - MN that connect the output terminals OUTO - OUT-N to the VS terminal. The VS terminal can be connected to a power supply such as the one shown in 1 and provide power to an LED array connected to output terminals OUTO - OUT-N. Each switch M0 - MN may be configured to control the current for the respective output terminal and operate independently of any other respective switch. In some examples, the switches, as controlled by the driver circuits, may control the current based on the duty cycle of a PWM scheme.

In the example of 4 The LED array control circuit 400 also includes a power supply section 402, an ESD protection 404, a digital communication 415, and a current sensing MUX 414. The LED array control circuit 400 includes driver circuits channel 0 through channel M. The example driver circuit 412 for channel 0 further includes a driver logic 416, a temperature sensor 420, a gate control and charge pump circuit 420, a load current sensor circuit 424, an overvoltage clamp circuit 426, and an overcurrent protection circuit 418. In other examples, the LED array control circuit 400 may also include more or less than the circuits shown in FIG. 4 shown. In some examples, driver logic 416 may control the duty cycle of switch M0 via gate control and charge pump circuitry 422.

The gate control and charge pump circuit 422 may use some form of switching device to control the connection of a supply voltage across a load through a charge storage device such as a capacitor. The gate control and charge pump circuit 422 may scale the voltage to the gates of the switches M0-MN.

The power supply part 402 is connected to VDD, which is further connected to a system power supply such as the one with respect to the 2 and 3 described. The power supply portion 402 may act as a DC-DC converter and provide one or more voltage sources, such as a reference voltage (e.g., Vref), to operate the components of the LED array control circuit 400. In some examples, the components of the LED array control circuit 400, such as the driver circuit 412 and the digital communication 415, may operate at different voltage levels from one another.

The ESD protection circuit 404 may include clamping circuits, filter circuits, and similar circuits to protect the components of the LED array control circuit 400 from electrostatic discharge (ESD) and other types of electromagnetic interference (EMI). The ESD protection circuit is connected between the digital communication interface 415 and individual input pins 405 and the load current sense terminal IS. The load current sense terminal IS is similar to that described above with respect to the 2 and 3 The digital communication interface 415 and the individual input pins 415 and the load current detection terminal IS can be connected to the processing circuitry such as the processing circuitry 120 and the microcontroller 220 and the microcontroller 320 described above in the 1-3 The digital communication interface 415 functions as described above with respect to 2 described communication interface 215.

The overcurrent protection circuit 418 functions as described above for the current limiting circuit 214, which is 2 and 3 described to protect the LEDs in the output array as well as other components of the LED array control circuit 4 from damage caused by overcurrent. In some examples, the overcurrent protection circuit 418 may be configured to output a signal indicative of an overcurrent condition via the digital communication circuit 415. In some examples, the overcurrent protection circuit 418 may cause the driver logic 416 to reduce the duty cycle or to completely turn off the switch in question, e.g., switch M0.

The overvoltage clamp circuit 426 may monitor the voltage at the output terminal OUTO to protect the LED string connected to channel 0 against overvoltage. Each channel, e.g., channel 0 - channel N, may include a similar overvoltage protection circuit.

The temperature sensor 420 can measure the temperature of the components of channel 0 including driver circuit 412 and switch M0. In some examples, each channel may include a similar temperature sensor circuit. In some examples, temperature sensor 420 may provide an input to logic driver 416, which may cause driver logic 416 to adjust the duty cycle of switch M0 in response to a change in temperature. For example, if the temperature exceeds a threshold, the signal from temperature sensor 420 may cause driver logic 416 to decrease current by changing the duty cycle or by turning switch M0 off. In some examples, driver logic 416 may increase the duty cycle or turn switch M0 on when the temperature decreases below the threshold.

In other examples, the processing circuitry such as that shown in 2 The microcontroller 220 shown may be configured to receive a signal from the LED array control circuit 400 that includes the temperature of a respective switch for an LED string. For example, the digital communication circuit 415 may receive the signal from the temperature sensor 420 and send the signal to the processing circuit. The processing circuit may determine whether the temperature exceeds a temperature threshold. In response to determining that the temperature exceeds a temperature threshold, the processing circuit may send a signal to the LED array control circuit 400 to open the respective switch to turn off the respective LED string or to adjust the duty cycle to reduce the current at the respective output terminal. The example of 4 shows a temperature sensor, e.g., temperature sensor 420, for each channel of LED array control circuit 400. In other examples, as described above with respect to 1 As described, an LED array control circuit may have a single temperature sensor or a temperature sensor for a group of channels.

Similarly, load current sensing circuit 424 may monitor the current in channel 0, and each channel may include a similar load current sensing circuit. Load current sensing circuit 424 operates similarly to that described above with respect to the 2 and 3 described current sensing circuits 216. The load current sensing circuit 424 may determine the current through the switch M0 and output a signal to the driver logic 416. In response to the signal from the load current sensing circuit 424, the driver logic 416 may cause the duty cycle for the switch M0 to change. In some examples, the driver logic 416 may output the signal with the sensed current to the current sensing MUX 414. As described above with respect to 1 As described, a separate load current sensing circuit for each channel, e.g., load current sensing circuit 424, may provide benefits such as improved current accuracy for an LED array control circuit according to this disclosure.

The current sense MUX 414 operates similarly to the one described above with respect to the 2 and 3 described current sense MUX output port 240. The current sense MUX 414 may determine the current level for each channel of the LED array control circuit 400 and output the information to a processor circuit via the sense port IS. In some examples, the current sense MUX 414 may receive a signal from the processor circuit to select a particular channel, determine the current level including the average current, peak current, and similar values, and output the information on the sense port IS.

5 is a block diagram illustrating a multi-channel high-side switch integrated circuit driven by individual input pins for each LED string. The LED array control circuit 500 illustrates another example of an LED array control circuit as described above with respect to the 1 - 4 Features and configurations of any LED array control circuit of this disclosure may be combined in any combination with the features and configurations of any other of the examples of this disclosure.

As above with the examples of 1 - 4 As described, the LED array control circuit 500 includes output terminals OUTO - OUT-N connected to the VS terminal through switches M0 - MN. The switches M0 - MN are controlled by the driver circuits for channel 0 through channel N, such as the driver circuit 512 for channel 0. The example LED array control circuit 500 also includes a power supply section 502, a sense output 508, an ESD protection and input logic 504, and a ground circuit 510.

The power supply part 502 is similar to that described above with respect to 4 described power supply part 402. In the example of the LED array control circuit 500, the power supply part 502 receives power from the VS pin instead of a separate VDD pin. Each of the LED array control circuits of this disclosure may also include the same configuration as the LED array control circuit 500. The power supply part 502 may include a supply voltage monitoring circuit 503 and an internal Power supply 506 is included. The internal power supply 506 may provide one or more voltage sources to operate the components of the LED array control circuit 500.

The sense output 508 may receive and process the sensed signals from the driver circuits for channels 0-N. As described above for the LED array control circuits 110-410, the sense output 508 may include a MUX to receive the sensed current from a current sense circuit associated with each channel, such as the load current sense circuit 524. In some examples, the sense output may receive additional sensed signals, such as temperature, an overcurrent flag, an overvoltage flag, a voltage at each output terminal, and similar sensed signals. The sense output 508 may provide the sensed signals to the IS terminal, which may be connected to the I/O port as described above with respect to the 1 - 3 described, may be coupled to one or more processor circuits. A processor circuit may select which channel to monitor by sending a signal through the ESD protection and input logic circuit 504 via the select pin DSEL.

As with the above with regard to 4 As described above, the ESD protection and input logic circuit 404 can protect the components of the LED array control circuit 500 from electrostatic discharge (ESD) and other types of electromagnetic interference (EMI). As with the 3 and 4 As described, each input terminal In ₀ - In- _N can receive a separate PWM scheme that controls the current in each channel via driver circuits and switches M0 - MN such as driver circuit 512. Although in 5 not shown, the LED array control circuit 500 may also include digital communication circuitry that may not be connected based on the application using the LED array control circuit 500. The ground circuit 510 may include filtering or other circuitry that may operate in conjunction with the ESD protection and input logic circuit 504.

The driver circuit 512 represents an example of the driver circuits for the channels 0 - N included in the LED array control circuit 500. The example of the driver circuit 512 includes a voltage sensor 532, an over-temperature circuit 520 connected to a temperature sensor 530, a gate control and charge pump 522, an over-current protection circuit 518, a load current detection circuit 524, and an output voltage limiting circuit 526. Components of the driver circuit 512 may have the same functions and features as the components of the related 4 described driver circuit 412. For example, the description of gate control and charge pump circuit 422 applies to gate control and charge pump circuit 522, overcurrent protection circuit 418 applies to overcurrent protection circuit 518, overvoltage clamp circuit 426 applies to overvoltage limiting circuit 526, and load current sensor circuit 424 applies to load current sensor circuit 524.

In some examples, the over-temperature circuit 520 operates similarly to the temperature sensor 420, except that the example of the LED array control circuit 512 shows a separate temperature sensor 530 included in the switch M0. The over-temperature circuit 520 may include circuitry, as with the temperature sensor 420, to amplify, filter, and compare a signal from the temperature sensor 530 to one or more thresholds.

The voltage sensor 532 may monitor the voltage at the output terminal OUTO, which may be connected to an LED string as part of an LED array. In some examples, the voltage sensor 532 may be included as part of the output voltage limiting circuit 526.

As with the 4 The driver logic 516 shown in the figure can be used to 5 Receive input signals from the components of driver circuit 512 and adjust the current to output terminal OUTO in response to those signals. Driver logic 516 may include circuitry to decrease the duty cycle of switch M0, for example, in response to an overtemperature signal from overtemperature circuit 520 or overcurrent protection circuit 518. In some examples, driver logic 516 may communicate with processor circuitry, e.g., via input terminal In ₀ , to receive a PWM signal to control switch M0, or via a MUX included in sense output 508 to output one or more signals from the components in driver circuit 512.

6 is a flowchart illustrating an example method for an initialization phase of a system for controlling an LED array according to one or more techniques of this disclosure. The steps of 6 describe an example of an interaction between a processing circuit 120A and an LED array control circuit 110A. Although the 6 described steps may apply to any of the examples of this disclosure, 6 , unless otherwise stated give, in relation to 1 The processing circuit 120A functions similarly to the processing circuit 120, and the LED array control circuit 110A functions similarly to the LED array control circuit 110, as shown in 1 shown.

A processor circuit such as processing circuit 120A may determine an initial voltage for an LED array such as LED array 160 controlled by LED array control circuit 110A. Because LED array 160 may include multiple LED strings and the LED strings may include LEDs of different types, processing circuit 120A may determine the LED type from a digital communication circuit, such as that shown in 2 illustrated digital communication circuit 215 (600). In response, digital communication circuit 215 may output the LED type or, in some examples, a maximum startup voltage to processing circuit 120A (602). Processing circuit 120A may receive the LED type or voltage information and command power supply circuit 130 to supply an initial voltage to the VS terminal as shown in 1 shown, output (604).

In some examples, the processing circuit 120A may be configured to set an initial voltage for the power supply circuit 130 without first sending a request to the LED array control circuit 110A for LED information. For example, an LED array control circuit 110A may not include a digital communication circuit 215, or the digital communication circuit 215 may be disconnected in some applications. In still other examples, the system 100 may be configured to initialize itself without request steps 600-604, for example, either the processing circuit 120A or the LED array control circuit 110A may be programmed with the initial start-up voltage by a user during assembly. In any of the examples, the processor circuit may enable the power supply circuit to output the initial voltage to the LED array via the LED array control circuit.

The LED array control circuit 110A may receive the initial voltage at the VS terminal and activate at least two switches controlling at least two respective LED strings of the plurality of LED strings in the LED array 160 (610). In some examples, the processing circuit 120 may cause a driver logic portion of a driver circuit, e.g., the driver circuit 412, to activate the switches (608). In other examples, the processing circuit 120A may directly activate the at least two switches, e.g., via input terminals In ₀ - In- _N .

A current measuring circuit such as the load current sensor circuit 424 of 1 may output the LED string current for each LED string of the LED array 160 (612). The processing circuit 120 may receive a respective current level for each activated LED string of the multiple LED strings. In some examples, the processing circuit 120 may receive the current via the MUX for each LED string of the LED array 260 regardless of whether the LED string is one of the activated LED strings or not. The processing circuit 120 may continue to cycle through each LED string or activated LED string to monitor the current throughout the initialization phase as well as periodically during the operation phase.

The processing circuit 120A may determine a respective voltage level for each LED string of the plurality of LED strings. For example, the voltage sensor 532 may be in 5 the voltage of the output terminal OUTO. In some examples, the processing circuit 120A may output the voltage of the output terminal OUTO - OUT-N through the sense terminal IS via the MUX, e.g. as shown in the 2 , 3 and 5 shown, received through the sense output 508 or the load current sense port 240. In other examples, the processing circuit 120 may receive the output voltage information via the 2 received digital communication circuit shown.

In response to receiving the respective voltage level for each LED string, the processing circuit 120A may determine the LED string with the largest voltage level with respect to the remaining LED strings of the plurality of LED strings (614). In the example of the LED array 160 in 1 the string with the highest voltage level may be the string with the largest number of LEDs, such as the LED string connected to OUT3 or the LED string connected to both OUT5 and OUT6. For example, if the LED voltage drop for each LED in the string connected to OUT3 is greater than the voltage drop for LEDs in the string connected to OUT5 and OUT6, then OUT3 with four LEDs may have the highest voltage level.

In some examples, the voltage ramp portion of the initialization phase may stop when all branches have reached at least a predetermined target current. As discussed above with respect to 1 As described, the LED array control circuit 110A may be configured to ensure that each active output OUTO - OUT-N has approximately the same average current. The processing circuit 120A may determine a PWM scheme and associated duty cycle for each switch M0 - MN such that the current for each branch (OUTO - OUT-N) is approximately equal to the current in the other branches. The voltage into the VS terminal may therefore be defined by the output voltage of the output terminal that powers the LED string with the highest forward voltage, in this example OUT3. The predetermined target current may be selectable based on the application, e.g., interior lighting, headlights, or similar application, which may include the types and number of LEDs in the LED array 160.

The processing circuit 120A may store the operating voltage value, the PWM scheme, and the highest forward voltage in a memory location. In some examples, the memory location may be integrated into the processing circuit 120A, such as in the example of a microcontroller. In other examples, the memory location may be separate from the processing circuit 120A. In response to determining the LED string with the largest voltage magnitude, the processing circuit 120A may adjust the voltage supply circuit, e.g., the power supply 130, to output an operating voltage for the LED array (616). Once the processing circuit 120A adjusts the operating voltage, the processing circuit 120A may adjust the individual duty cycle for the PWM scheme for each driver circuit channel controlling the switches M0-MN. In other words, in response to adjusting the operating voltage, the processing circuit 120A may adjust the operating pulse width modulation (PWM) scheme for each respective switch of each respective LED string such that the current in each LED string approximates a predetermined current. Each respective PWM scheme for each respective switch M0-MN may be adjusted independently of the remaining switches.

In some examples, processing circuitry 120A may communicate, via digital communication circuitry such as digital communication circuitry 215 and 415, current limiter settings for overcurrent protection circuitry, such as overcurrent protection circuitry 418 and overcurrent protection circuitry 518, as shown in FIGS. 4 and 5 shown (618). The digital communication circuit may set the current limit in each respective overcurrent protection circuit for each channel. The digital communication circuit may also program each respective driver circuit with the PWM scheme and current limit settings (620). In some examples, the digital communication circuit may also receive other system protection limits from the processing circuit and set those limits in the components of the driver circuits, such as overvoltage, temperature thresholds, and similar limits.

In other examples, current limits may be programmed into a system by a user during assembly. For example, an LED array control circuit for use in controlling interior lighting may be programmed with expected overcurrent limits, along with overvoltage, overtemperature, and other safety limits, during the assembly and installation process. During assembly and installation, a user may understand the number and types of LEDs used for the interior lighting and may set the system protection limits based on that understanding.

7 is a flowchart illustrating an example method for an operating phase of a system for controlling an LED array according to one or more techniques of this disclosure. The operating phase may begin after the initialization phase of 6 , as shown by block “B” in the 6 and 7 indicated, is completed. The steps of 7 are related to the 1 - 5 and describe an example of an interaction between a processing circuit 120B and an LED array control circuit 110B. Similar to the processing circuit 120A and the LED array control circuit 110A described above with respect to 6 , the processing circuit 120B operates similarly to the processing circuit 120 and the LED array control circuit 110B operates similarly to the LED array control circuit 110 as described in 1 are shown.

The LED array control circuit 110B may be powered at the VS terminal from a power supply such as the one shown in 2 illustrated voltage regulator 230 receives an operating voltage (622). As above with respect to 6 As described, the operating voltage may be based on the LED string in an LED array with the highest total forward voltage. After a predetermined time interval, the LED array control circuit may output an updated temperature and current for each channel (624). The current may include the average current based on the duty cycle of the PWM scheme for the channel. In some examples, the digital Communication circuitry may determine the time interval and channels for which to output the current and temperature information. In other examples, processing circuitry 120B may select the channels to receive the updated current and temperature information (626).

The processing circuit 120B may determine whether the second, updated respective current for an LED string is within a threshold range of the predetermined current (628). In response to determining that the updated respective current for the LED string exceeds the threshold range of the predetermined current, the processing circuit 120B may adjust the respective PWM scheme for the LED string (630), e.g., by adjusting the duty cycle of the signal controlling the gate of the switch for the channel. If the processing circuit 120B determines that the current does not exceed the current threshold (NO in branch of 628), the processing circuit need not make any adjustments and waits for the next set of updated current measurements.

Similarly, processing circuitry 120B may determine whether a temperature of a respective switch for an LED string exceeds a threshold temperature (638). In response to determining that the temperature exceeds a current threshold, processing circuitry 120B may decrease the average current to the respective LED string, e.g., by adjusting the duty cycle (630). In some examples, processing circuitry 120B may turn off the switch, i.e., set the duty cycle to zero.

The LED array control circuit 110B may receive the commands to update the PWM scheme for a channel (632) either via the digital communication circuit or directly, such as using the input terminals In ₀ - In- _N. After a predetermined time interval, the LED array control circuit 110B may output an updated temperature and current for each channel (624). In other examples, as described above with respect to the 4 and 5 As described, the respective driver logic may adjust the duty cycle of the respective switch for the channel based on current, temperature, or other sensing information without input from the processing circuit 120B.

The processing circuitry 120B may further determine that a current for the LED string with the highest voltage magnitude exceeds a threshold range of the predetermined current magnitude (634). In other words, the current in the channel with the LED string having the highest total forward voltage has exceeded a current threshold. In some examples, the processing circuitry 120B may adjust the PWM scheme as described above (630). In other examples, the processing circuitry 120B may determine that the current for the channel with the highest total forward voltage has exceeded a predetermined range of the current threshold and may adjust the power supply voltage (636). For example, a predetermined threshold current for the LED array may be set to 100 mA. The processing circuitry may adjust the duty cycle of the PWM scheme to increase or decrease the current for a given channel to maintain the 100 mA. The current may vary based on temperature or other factors. If the current exceeds a range of the current threshold, such as a range of ±20 mA from the 100 mA threshold (i.e., a range of 80 mA to 120 mA), the processing circuit 120B may adjust the output voltage of the power supply connected to the VS terminal of the LED array control circuit (636). In other words, in response to determining that the current for the LED string with the largest voltage level exceeds a threshold range of the predetermined current, the processing circuit 120B may adjust the operating voltage from the power supply circuit to the LED array from a first operating voltage to a second operating voltage. Going beyond a range is merely one example of a triggering criterion for the processing circuitry 120B to adjust either the PWM scheme or the regulator voltage. Other examples of triggering criteria may be used as well. If the current for the highest voltage string does not exceed the triggering criterion (NO of 634), the processing circuitry 120B may wait for the next updated current and other sense information (626).

In one or more examples, the functions described above may be implemented in hardware, software, firmware, or any combination thereof. For example, the various components of the 1 - 3 such as the processing circuit 120 and the microcontroller 220 may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted via a computer-readable medium as one or more instructions or code and may be executed by a hardware-based processing ing unit. Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communications media comprising any medium that facilitates the transfer of a computer program from one location to another, e.g., according to a communications protocol. In this way, computer-readable media may generally correspond to (1) tangible computer-readable storage media that is non-transitory, or (2) a communications medium such as a signal. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and/or data structures for implementing the techniques described in this disclosure. A computer program product may include a computer-readable medium.

By way of example and without limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. In addition, any connection is properly referred to as a computer-readable medium. For example, if instructions from a web page are transmitted from a server or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It is to be understood, however, that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but instead refer to non-transitory, tangible storage media. Disc and disk, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disc, and Blu-ray disc, with disks typically reproducing data magnetically while discs reproducing data optically using lasers. Combinations of the above should also be included within the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one or more DSPs, microcontrollers, general purpose microprocessors, ASICs, FPGAs, or other equivalent integrated or discrete logic circuitry. Accordingly, the term "processor" as used herein, such as processing circuitry 120, microcontroller 220, and microcontroller 320, may refer to any of the foregoing structures or any other structures suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein may be provided within associated hardware and/or software modules configured to encrypt and decrypt. Additionally, the techniques could be implemented entirely in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide variety of devices or devices, including an integrated circuit (IC) or a set of ICs (e.g., a chipset). Various components, modules, or units are described in this disclosure to highlight functional aspects of devices configured to perform the disclosed techniques, but they do not necessarily require implementation by different hardware units. Rather, different units may be combined in a hardware unit as described above, or provided by a collection of interoperable hardware units including one or more microprocessors as described above, in conjunction with appropriate software and/or firmware.

Claims (16)

Light emitting diode (LED) array control circuit, wherein the control circuit (110; 210; 310; 400) comprises: a plurality of output terminals (OUTO - OUT-N), wherein each of the plurality of output terminals (OUTO - OUT-N) is designed to control a respective LED string of an LED array (160; 260); a plurality of current measuring circuits (216-0, 216-N), each of which is designed to determine a current intensity for a respective output terminal (216-0, 216-N); a plurality of switches (M ₀ , M _N ), a plurality of driver circuits (212-0; 212-N) having a plurality of current limiting circuits (214-0, 214-N); and a plurality of temperature sensors (420) each associated with one of the plurality of switches (M ₀ , M _N ), wherein: each of the plurality of switches (M ₀ , M _N ) is configured to control the current for a respective output terminal (OUTO - OUT-N) and to operate independently of any other of the switches (M ₀ , M _N ), wherein: each of the plurality of driver circuits (212-0; 212-N) is configured to operate a respective switch (M ₀ , M _N ) of the plurality of switches, each of the plurality of current limiting circuits (214-0, 214-N) is associated with a respective switch (M ₀ , M _N ) of the plurality of switches (M ₀ , M _N ), and each of the plurality of current limiting circuits (214-0, 214-N) is configured to control the operation of the respective switch (M ₀ , M _N ) associated with the respective current limiting circuit (214-0, 214-N) to limit the current for each respective output terminal (OUTO - OUT-N), and wherein each of the plurality of temperature sensors (420) is configured to compare a temperature of the switch (M ₀ , M _N ) associated therewith with a temperature threshold and, in response to the sensed temperature exceeding the temperature threshold, to turn off the switch or change a duty cycle of the switch. Control circuit according to claim 1 , wherein the plurality of switches (M ₀ , M _N ) are configured to control the current intensity based on pulse width modulation (PWM). A control circuit according to any preceding claim, wherein each of the plurality of driver circuits (212-0; 212-N) further comprises an overvoltage protection circuit (426). Control circuit according to one of the preceding claims, further comprising a digital communication circuit (215; 315; 415) configured to communicate with one or more processor circuits (220; 320). Control circuit according to one of the preceding claims, wherein the control circuit (110; 210; 400) is adapted to determine a voltage at each of the plurality of output terminals (OUTO - OUT-N). Control circuit according to one of the preceding claims, further comprising a detection terminal (240) and a multiplexer (MUX) circuit, wherein the MUX circuit is configured to receive information from each driver circuit (212-0; 212-N) of the plurality of driver circuits (212-0; 212-N) and to output the information to the detection terminal (240), wherein the information output at the detection terminal (240) comprises a respective current strength for a respective output terminal (OUTO - OUT-N). Control circuit according to claim 6 , wherein the current limiting circuits (214-0, 214-N) are designed to limit the respective current intensity so that it is not higher than a respective LED maximum current. Control circuit according to one of the preceding claims, wherein the control circuit (110; 210; 400) is implemented as an integrated circuit (IC). A method of controlling a light emitting diode (LED) array, the method comprising initializing an LED control circuit (110; 210; 310; 400) by a processor circuit (120; 220; 320), the initialization comprising: determining an initial voltage for an LED array (160; 260) controlled by an LED control circuit (110; 210; 310; 400) by the processor circuit (120; 220; 320), the LED array (160; 260) comprising a plurality of LED strings, and the LED control circuit (110; 210; 310; 400) comprising a respective switch (M ₀ , M _N ) to operate each LED string; Activating, by the processor circuit (120; 220; 320), a voltage supply circuit (130; 230) to output the initial voltage to the LED array; activating, by the processor circuit (120; 220; 320), at least two switches (M ₀ , M _N ) controlling at least two respective LED strings of the plurality of LED strings; receiving, by the processor circuit (120; 220; 320), a respective current magnitude for each activated LED string of the plurality of LED strings; receiving, by the processor circuit (120; 220; 320), a respective voltage magnitude for each LED string of the plurality of LED strings; determining, by the processor circuit (120; 220; 320), the LED string having the greatest voltage magnitude with respect to the remaining LED strings of the plurality of LED strings in response to receiving the respective voltage magnitude for each LED string; Adjusting the power supply circuit (130; 230) to output an operating voltage to the LED array (160; 260) by the processor circuit (120; 220; 320) in response to determining the LED string having the greatest voltage level; determining a pulse width modulation (PWM) scheme for each respective switch of each respective LED string such that the current in each LED string is approximately a predetermined current, by the processor circuit (120; 220; 320) in response to adjusting the operating voltage, wherein each respective PWM scheme for each respective switch is adjusted independently of all other switches (M ₀ , M _N ) of the plurality of switches (M ₀ , M _N ); comparing a temperature of each of the switches (M ₀ , M _N ) to a temperature threshold and turning off the switch (M ₀ , M _N ) or changing a duty cycle of the switch (M ₀ , M _N ) in response to the sensed temperature exceeding the temperature threshold. procedure according to claim 11 , wherein the respective current level for each activated LED string is a first respective current level for each activated LED string, the method further comprising operating the LED array (160; 260), wherein operating the LED array (160; 260) comprises: receiving, by the processor circuit (120; 220; 320), a second respective current level for each activated LED string of the plurality of LED strings; determining, by the processor circuit (120; 220; 320), whether the second respective current level for a first LED string is within a threshold range of the predetermined current level; and adjusting, by the processor circuit (120; 220; 320), the respective PWM scheme for the first LED string in response to determining that the second respective current level for the first LED string exceeds the threshold range of the predetermined current level. procedure according to claim 9 further comprising operating the LED array, wherein operating the LED array comprises: determining, by the processor circuit (120; 220; 320), that a current for the LED string having the greatest voltage magnitude exceeds a threshold range of the predetermined current magnitude; and adjusting, by the processor circuit (120; 220; 320), the operating voltage from the power supply circuit (130; 230) to the LED array (160; 260) from a first operating voltage to a second operating voltage in response to determining that the current for the LED string having the greatest voltage magnitude exceeds the threshold range of the predetermined current magnitude. A system comprising: a light emitting diode (LED) array (160; 260) having a plurality of LED strings; an LED control circuit (110; 210; 310; 400) according to one of the Claims 1 until 8 operatively coupled to the LED array (160; 260); a processor circuit (120; 220; 320) operatively coupled to the LED control circuit (110; 210; 310; 400). system according to claim 12 : wherein each respective driver circuit (212-0; 212-N) comprises the respective current measuring circuit (216-0, 216-N); and wherein the processor circuit (110; 210; 310; 400) is configured to receive the information output from the sensing terminal (240). system according to claim 13 , the system further comprising a power supply circuit (130; 230) configured to supply power to the LED array (160; 260), the processor circuit (120; 220; 320) configured to: activate the power supply circuit (130; 230) to output a first voltage to the LED array (160; 260); activate at least two switches (M ₀ , M _N ) controlling at least two respective output terminals (OUTO - OUT-N) of the plurality of output terminals (OUTO - OUT-N); receive a respective current level from the sense terminal (240) for each activated LED string of the plurality of LED strings; receive a respective voltage level for each LED string of the plurality of LED strings; in response to receiving the respective voltage level for each LED string, determining the LED string having a greatest voltage level relative to the remaining LED strings of the plurality of LED strings; in response to determining the LED string having the greatest voltage level, adjusting the power supply circuit (130; 230) to output a second voltage to the LED array; and in response to adjusting the second voltage, determining a pulse width modulation (PWM) scheme for each respective switch of each respective LED string such that the current in each LED string is approximately a predetermined current level, wherein each respective PWM scheme is adjusted for each respective switch (M ₀ , M _N ) independently of all other switches of the plurality of switches. system according to claim 14 , wherein the respective current intensity for each activated LED string is a first respective current intensity for each activated LED string, and wherein the processor circuit (120; 220; 320) is further configured to: receive a second respective current intensity for each activated LED string of the plurality of LED strings determine whether the second respective current for a first LED string is within a threshold range of the predetermined current; and in response to determining that the second respective current for the first LED string exceeds the threshold range of the predetermined current, adjust the respective PWM scheme for the first LED string. system according to claim 12 , wherein the processor circuit (120; 220; 320) is further configured to: receive from the LED control circuit (110; 210; 310; 400) a signal comprising a temperature of a respective switch (130; 230) for an LED string; determine whether the temperature exceeds a threshold temperature; and in response to determining that the temperature exceeds a threshold temperature, send a signal to the LED control circuit (110; 210; 310; 400) to adjust a duty cycle of the respective switch (M ₀ , M _N ) for the respective LED string.

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