WO2024160718A1

WO2024160718A1 - An led lighting arrangement

Info

Publication number: WO2024160718A1
Application number: PCT/EP2024/052052
Authority: WO
Inventors: Peng Chen; Jianqing Tang; Bertrand Johan Edward Hontele
Original assignee: Signify Holding BV
Current assignee: Signify Holding BV
Priority date: 2023-02-01
Filing date: 2024-01-29
Publication date: 2024-08-08
Anticipated expiration: 2025-08-01

Abstract

An LED lighting arrangement having a power converter with feedback control. A command signal controls which, if any, of one or more LED channels are active. A sense signal is passed to a controller of the power converter responsive to the state of each LED channel, such that the controller receives indirect feedback about the command signal. In particular, the controller is effectively decoupled from the command signal. The controller controls the power converter to supply a driving signal being a first current responsive to the sense signal indicating the switch controller permitting current flow through not all of the one or more LED channels; and a second, larger current responsive to the sense signal indicating the switch controller permitting current flow through all of the one or more LED channels.

Description

AN LED LIGHTING ARRANGEMENT

FIELD OF THE INVENTION

The present invention relates to the field of lighting, and in particular to LED lighting arrangements.

BACKGROUND OF THE INVENTION

The use of artificial lighting is becoming increasingly common, with LED lighting arrangements becoming more popular due to their high energy efficiency and flexibility of use. One form of LED lighting arrangement is a so-called “Scene SWitch" (SSW) arrangement, which is able to switch between different lighting states or lighting scenes responsive to the toggling of a power supply switch, being an external switch between a power source (such as a mains supply) and the LED lighting arrangement. One example of a power supply switch, common in ceiling installations, is a wall switch.

Generally, an SSW lighting arrangement is able to cycle or step through a sequence of lighting states or lighting scenes responsive to a toggling of the power supply switch. This provides a straightforward and intuitive mechanism for user-defined control over the lighting state of the SSW lighting arrangement.

A typical SSW lighting arrangement comprises two or more LED channels (e.g., strings of one or more LEDs), with a buck converter for each channel. Different LED channels output different forms of light (e.g., different color temperatures and/or colors). A sensing circuit is responsible for sensing the toggling of the power supply switch, and controls which of the buck converters are active and driving their respective LED channel. This allows control over the form of light output by the overall SSW lighting arrangement. For instance, for a two-channel SSW lighting arrangement, four different states are possible: No Light; First Channel Only; Second Channel Only; and Both Channels.

A significant drawback of existing SSW lighting arrangements is that a buck converter takes up significant space, due to the relatively large components that make up a buck converter, such as an inductor, electrolytic capacitor and so on. As existing configurations of SSW lighting arrangements require a buck converter for each LED channel, the size of the lighting arrangement is significantly increased. The use of multiple buck converters can also introduce power loss (through the use of additional components) and/or affect a power factor of the SSW lighting arrangement (through increased reactive current).

These challenges make it difficult for a designer of an SSW lighting arrangements to make slim and/or power efficient designs.

A common design is using a single power supply to drive all the LED channels, and at each channel to provide a channel switch. The channel switches are controlled by command signals to activate selected LED channels, whereas the single power supply is also controlled by the command signal to output an adjustable output power thereby the output power corresponding to the activated LED channels. A drawback is that if the LED channel is not activated due to delay or switch failure but the power supply has already been adjusted, there would be asynchronization between the output power and the LED channels that are driven by the output power. In some conditions, the output power of the lighting arrangement is not as expected. In even worse conditions, the output power would overpower the LED channel and damage the lighting arrangement.

US20110248648 Al, WO2011021850A2 and US20090322234A1 disclose regulating the output voltage of a driver to one or more parallel LED string for reducing the voltage difference between the output voltage and a maximum forward voltage of the LED strings.

SUMMARY OF THE INVENTION

The invention is defined by the claims.

The proposed invention overcomes the abovementioned problems by providing an LED lighting arrangement with a single power converter whose output power is able to adapt for driving different numbers of LED channels wherein the single power converter on itself regulates the output power depending on the states of the LED channels. In particular, on one hand, a number of active LED channels is controlled by a command signal operating a channel switch connected to the LED channel; on the other hand, the power converter, on its own, directly senses how many LED channels are activated and controls power output of the power converter based on the number of active LED channels, i.e., LED channels that are conducting electricity. This sensing is achieved by providing a detecting circuit from the LED channel to the controller via a level shifter, a buffering transistor and/or an isolation element such as an optocoupler, to thereby feed an electric measure of the LED channel to the controller. Effectively, control of the power converters output is decoupled or electrically isolated from the command signal to the active LED channels, in other words, the power converter does not directly use the command signal to adjust its output power but instead only directly senses the electric on the LED channel. Only after the LED channel has been successfully switched, the electric on the LED would change, and the power converter would respond to adjust its output power. This avoids the above- mentioned problem of asynchronization between the power converter and the failed activation/deactivation of the LED channels. A further advantage is that since the LED channel and the power converter are controlled separately by different signals, LED channels and (the controller of) the power converter are able to operate whilst referencing different reference grounds. This allows a power converter that outputs a power signal with its own floating reference ground (e.g., a buck converter or a buck-boost converter) to be used.

The proposed approach thereby overcomes problems in driving one or more LED channels that have not previously been addressed. More particularly, the proposed approach provides approaches for driving or powering one or more LED channels that does not require a plurality of separate power converters to regulate the power to the LED channels.

According to examples in accordance with an aspect of the invention, there is provided an LED lighting arrangement comprising: a power converter configured to supply a driving signal; one or more LED channels configured to receive the driving signal, each LED channel comprising one or more LEDs configured to generate light; one or more channel switches each of which electrically connected with a respective one of the one or more LED channels; a command interface configured to receive a command signal for controlling the one or more LED channels; a switch controller electrically connected between the command interface and each channel switch, the switch controller being configured to control the operation of each channel switch so as to selectively activate the one or more LED channels responsive to the command signal; a sensing circuit electrically connected with the one or more LED channels, and configured to sense an electrical parameter of electricity drawn by the one or more LEDs channels resulting from the switch controller controlling the operation of the one or more channel switches and produce a sense signal based the sensed electrical parameter; and a power converter controller coupled to the sense signal and electrically connected to the power converter, configured to control the power converter to supply a variable driving signal to the LED channels responsive to the sense signal, wherein said power converter controller is electrically unconnected to the command signal and adapted to control the power converter to supply the driving signal being: a first current responsive to the sense signal indicating the switch controller permitting current flow through not all of the one or more LED channels; and a second, larger current responsive to the sense signal indicating the switch controller permitting current flow through all of the one or more LED channels.

The proposed approach provides a LED lighting arrangement suitable for a Scene Switching (SSW) application without the need for a plurality of power converters (e.g., a plurality of buck converters). In particular, the proposed mechanism provides a system that allows the output current of a single power converter to be appropriately regulated for driving one or more LED channels responsive to the operation of a separate controller for controlling current flow through the LED channel(s). The disclosed approach allows a power converter to automatically react to a change in demand for electricity (current, power) by the LED channel(s) resulting from a controlled operation of the LED channel(s). However, the power converter is decoupled from the command signal for the LED channels. This is distinct to approaches that directly control the output of the power converter from the command signal that operate the LED channels to control the operation of the LED changes (i.e., active control approaches).

The proposed approach separates LED channel control from the control of the LED driver (i.e., the power converter), but instead provides a system for providing a converted or decoupled version of a command signal to the LED driver (power converter) to allow it to adapt to the change in LED channel demand.

More particularly, the disclosed approach proposes a direct sensing of the LED channel state to the power converter controller. The power converter controller does not receive the command signal directly, but instead responds to changes of current or power flow in the LED channel(s) as a result of the command signal. This allows the (inputs of the) power converter controller to be isolated or effectively isolated (i.e., decoupled) from the command signal, but still able to operate and regulate the power/current output by the power converter. Moreover, the power converter is controlled by the real/actual electrical states of the LED channels, e.g., rather than an estimated/expected version, thus the output current as driving signal for the LED channels can be provided more accurately and reliably. If the channel switch fails or is delayed such that the LED channels are not operated, the power converter can sense this and prevent changing the output current as driving signal.

The proposed approach avoids the need for multiple power converters to provide different levels of regulated power to the LED channel(s) responsive to a change in operation of the LED channel(s) by a command signal. The power converter may comprise any one or more of: a buck converter; a buck-boost converter; and/or an isolated converter formed of a transformer having a primary side galvanically connected to the power converter controller and a secondary side galvanically connected to the one or more LED channels.

The power converter may further comprise a switch component connected between the sensing circuit and the power converter controller, wherein: the switch component is configured to be driven by said sense signal and to generate a switch signal; and the power converter controller is electrically connected to the switch component and configured to receive said switch signal and regulate the output current as driving signal according to the switch signal.

This switch component can provide a simple signal conversion between the sense signal and the power converter controller. Optionally, the switch component could be a level shifter component, e.g., if the level of the sense signal and the level of the power converter controller are different.

In some examples, the sensing circuit is adapted to sense a different value for the electrical parameter resulting from the switch controller differently controlling the operation of the one or more channel switches; and each channel switch comprises a reference terminal electrically grounded to a first reference voltage; the switch controller is electrically grounded to the first reference voltage, such that the switch controller is able to directly drive each channel switch, optionally the switch controller is electrically connected to a control terminal of each channel switch; and the power converter and the power converter controller are both electrically connected to a second reference voltage, the second reference voltage being different to the first reference voltage.

The proposed LED lighting arrangement facilitates or takes account of the use of different reference or ground voltage levels. Thus, the LED lighting arrangement can be effectively divided into two portions with different ground voltage levels. Grounding the switch controller and the channel switch to the same first reference voltage can make the driving of the channel switch easier: an output of the switch controller can directly drive the channel switch without using a further driving circuit or level shifter. Further this embodiment is particularly useful if the power converter provides a floating driving voltage, e.g., a voltage that is not directly referenced to a global ground. Examples of such power converters include buck converter, buck-boost converters or isolated converters.

Optionally, each channel switch is connected between a cathode of an LED of a respective channel and the first reference voltage; and the sensing circuit is electrically connected to each cathode to which each channel switch is connected. In this embodiment, the cathode voltage of a LED channel is greatly dependent on the state/activation of said LED channel thus is a good indicator for the power converter controller. Those skilled understand that the sensing circuit can be connected to other location in the LED channel as long as the electric parameter at that location can indicate the state of the LED channel.

The LED lighting arrangement may comprise an optocoupler having a light emitting side electrically connected to the sensing circuit and a light receiving side electrically connected to the power converter controller. An optocoupler maintains effective galvanic isolation between the LED channels and the input(s) to the power converter controller.

In some examples, the light emitting side of the optocoupler is electrically connected to the first reference potential (if present); and the light receiving side of the optocoupler is electrically connected to the second reference potential (if present). This embodiment provides a level shifting from the first reference potential to the second reference potential. Those skilled in the art would understand that if the electrical parameter and the power converter controller are referencing to the same reference potential, such level shifting can be saved and the electrical parameter can be fed to the power converter controller directly.

As an alternative (or addition) to the opto-coupler, the switch component may comprise: a low voltage transistor having a base connected to the sensing circuit, a collector connected to the driving signal and an emitter connected to the first reference voltage, said low voltage transistor optionally being a NPN transistor; and a high voltage transistor having a base connected to the collector of the low voltage transistor; an emitter connected to the driving signal and a collector connected to the second reference voltage and the power converter controller, said high voltage transistor optionally being a PNP transistor.

In this embodiment, the bridge structure of the two transistors acts as a level shifter between the first reference voltage and the second reference voltage. This provides an alternative embodiment to the opto-coupler.

The switch component may further comprise a buffer transistor electrically connected between the collector of the high voltage transistor and the power converter controller. This provides (e.g. increased) signal coupling between the power converter controller and the electrical parameter of LED channel(s). The buffer transistor can improve or amplify the electrical parameter so as to control the power converter controller. In some examples, the LED lighting arrangement further comprises an input configured to receive an input power signal, wherein the power converter is electrically connected to the input and is configured to convert the input power signal to produce the driving signal.

In this embodiment, the power converter is an active power converter such as a switched-mode power supply to convert the input.

The LED lighting arrangement may further comprise a command signal generator electrically connected between the input and the command interface, the command signal generator being configured to generate the command signal responsive to any interruptions in the input power signal.

This embodiment applies the concept of the invention to the Scene Switch application and the power converter can be reliably controlled to provide output power corresponding to the switched LED channels, providing the desired lighting state.

In some examples, the LED lighting arrangement is configured wherein the switch controller is adapted to controllably permit or prevent current flow through each LED channel responsive to the command signal by closing the switch or deactivating the switch; the sensing circuit is configured to control the sense signal to have: a first magnitude responsive to the switch controller permitting current flow through not all of the at least one LED channel; and a second, different magnitude responsive to the switch controller permitting current flow through all of the at least one LED channel; and the power converter controller is adapted to regulate the output current as driving signal to have: a first level responsive to the sense signal having one of the first or second magnitude; and a second, different level responsive to the sense signal having the other of the first and second magnitudes.

In this embodiment, a relatively restricted or simple number of values, here: two values, can be used to indicate the number of LED channels activated, and power converter controller can distinguish those two values and control the power converter to provide two different outputs.

The power converter controller may regulate the output current as driving signal to have: a first current as the first level responsive to the switch controller permitting current flow through not all of at least one LED channel; and a second, larger current as the second level responsive to the switch controller permitting current flow through all of the one or more LED channels. In this embodiment, the more LED channels are activated, the more current the power converter will generate. Thus different brightness or other lighting characteristics can be switched automatically.

Preferably the LED channels have different color temperatures. This can switch the color temperature along with the brightness and the user’s experience is improved.

The one or more LED channels may comprise a plurality of LED channels connected in parallel. The parallel LED channels can split the current by themselves and achieve balance automatically.

The one or more channels switch may comprise a different channel switch for each LED channel, such that each channel switch controls the current flow through a respective LED channel, and wherein the sensing circuit comprises a common node to provide an initial of the sense signal and, for each channel switch, a respective diode coupled between a collector or emitter of the channel switch and the common node.

In this embodiment, this simple structure of two diodes can achieve a NAND logic operation to indicate whether all of the LED channels are activated. If not all of the LED channels are activated, the diode would be biased into a high voltage; otherwise it would be biased into a low voltage.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment s) described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

Fig. 1 illustrates an existing LED lighting arrangement;

Fig. 2 schematically illustrates a proposed lighting arrangement;

Fig. 3 illustrates one alternative for the proposed lighting arrangement;

Fig. 4 illustrates another alternative for the proposed lighting arrangement; and Fig. 5 illustrates a portion of a variation for the proposed lighting arrangement.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention will be described with reference to the Figures.

It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

The present invention provides an LED lighting arrangement having a power converter with a self-detecting control. A command signal controls which, if any, of one or more LED channels are active. A sense signal is passed to a controller of the power converter responsive to the state of each LED channel, such that the controller receives direct sensing of the LED channels, which thereby provides indirect information about the command signal. In particular, the controller is effectively decoupled from the command signal. This avoids or reduces the likelihood of the power converter outputting an output current as driving signal that does not match the LED channels which have not been switched by the command signal in time, due to delay or failure.

Proposed embodiments are also based on the realization that the power provided by many power converters is decoupled from a real or true ground, rather providing its own ground or reference point (e.g., a floating ground). Control over the operation of LED channels that are powered from such a power converter should therefore also be made with reference to this floating ground. However, the controller of the power converter should still operate with respect to the real ground or reference point, to avoid runaway control. The proposed approach provides sensing information for facilitating synchronized control of the power provided by the power converter, whilst decoupling the controller from the command signal, which is made with respect to the floating ground.

Disclosed approaches provide a reliable LED lighting arrangement that avoids the need for using multiple power converters whilst still providing variable light output by the LED lighting arrangement and/or selective driving of different LED channels.

Proposed embodiments can be employed in any environment or scenario in which lighting is desired, e.g., domestic, clinical, industrial, office, educational, public and/or outdoor environments.

Figure 1 is a schematic illustration of an existing LED lighting arrangement 100 for contextualizing the present invention. The LED lighting arrangement 100 comprises a power converter arrangement 110. The power converter arrangement 110 is configured to generate or supply driving signals Di, D2. In particular, the power converter arrangement 110 comprises a plurality of power converters 111 and 112, each configured to generate or supply a different driving signal Di, D2.

The LED lighting arrangement 100 comprises a plurality of LED power converters 111, 112. Each LED power converter is connected to one LED channel 121, 122 configured to generate light. A first LED channel 121 is driven by a first driving signal Di produced by the first power converter 111 and a second LED channel 122 is driven by a second driving signal D2 produced by the second power converter. Thus, each LED channel is associated with a respective power converter. The LED channels may have different lighting characteristics (e.g., different colors, temperatures, beam spread, beam uniformity and so on).

More particularly, each power converter 111, 112 of the power converter arrangement 110 is configured to convert a DC voltage VDC into a respective driving signal Di, D2. The DC voltage VDC may be produced by a rectifying and PFC arrangement 150 that rectifies a mains supply VAC and executes power factor correction. Each power converter may, for instance, be a buck converter. The DC voltage thereby acts as an input power signal. The rectifying arrangement 150 may form part of the LED lighting arrangement or part of a separate power supply arrangement.

When activated, each power converter 111, 112 is configured to regulate or control the power flow through its respective LED channel 121, 122such that the LED(s) LED1, LED2 of that LED channel emit(s) light. When deactivated, each power converter is configured to prevent power flow through its respective LED channel, to prevent the emission of light from that LED channel.

The LED lighting arrangement 100 also comprises a controller 130 configured to control the operation of the power converter arrangement 110. In particular, the controller controls whether or not the or each power converter 111, 112 supplies the respective driving signal Di, D2 to its respective LED channel, i.e., whether each power converter is activated or deactivated. The controller uses a first control signal Sci to control the operation (e.g., activate or deactivate) of the first power converter 111 and a second control signal Sc2 to control the operation of the second power converter 112.

The illustrated LED lighting arrangement 100 is configured, for example, as an SSW lighting arrangement. In particular, the operation of the controller 130 is responsive to a command signal Sc. The command signal changes when there is an interruption in the mains power supply provided to the LED lighting arrangement 100 (e.g., when a wall switch is toggled). The controller 130 may be configured to cycle through different lighting states by controlling which of the power converters are active via the control signals Sci, Sc2. For instance, the controller may cycle through, responsive to an interruption in the mains power supply VAC, the following sequence: power output by the first converter only; power output by the second converter only, and power output by both converters. In other applications, an infra-red remote can be used to replace the SSW.

In the existing LED lighting arrangement, each LED channel is driven by a separate, dedicated power converter. Control over whether an LED channel is driven (e.g., draws power) is controlled by controlling whether or not its respective power converter outputs a driving signal to that channel.

The existing LED lighting arrangement disadvantageously requires multiple power converters in order to facilitate control or switching between different lighting states.

Figure 2 illustrates a proposed LED lighting arrangement 200 according to the present application.

The LED lighting arrangement comprises a single power converter 210 configured to supply a (single) output current as driving signal D. The power converter 210 converts a DC power VDC, which may be provided by an optional rectifying and PFC arrangement 250 of the LED lighting arrangement 200. The DC voltage thereby acts as an input power signal.

The LED lighting arrangement comprises a plurality of LED channels 221, 222, each comprising one or more LEDs LED1, LED2 configured to generate light. Each LED channel 221, 222 is configured to receive the driving signal D. Thus, multiple LED channels receive a same driving signal D. The LED channels may optionally have different lighting characteristics (e.g., different colors, color temperatures, beam spread, beam uniformity and so on) in which the color, color temperature, total output beam pattern can be adjusted together with the adjusted brightness. Alternatively, LED channels may have same lighting characteristics in which case only the brightness can be adjusted.

It is not essential that there be a plurality of LED channels, rather, some embodiments may comprise only a single LED channel.

In the illustrated example, the LED channels are connected in parallel. In alternative examples, the LED channels are connected in series to one another. The LED lighting arrangement 200 comprises one or more channel switches QI, Q2 electrically connected with the LED channel(s). The channel switches QI, Q2 can be considered to form part of a switch arrangement 220. The operation of the channel switches controls the power flow through each LED channel. In the illustrated example, each LED channel 221, 222 is connected in series with a respective channel switch. Thus, each channel switch QI, Q2 controls the power flow through a different LED channel 221, 222.

The LED lighting arrangement comprises a command interface configured to receive a command signal Sc for controlling the one or more LED channels. The command signal may, for instance, change when there is an interruption in the mains power supply provided to the LED lighting arrangement 100 (e.g., when a wall switch is toggled).

The LED lighting arrangement 200 comprises a switch controller 230. The switch controller is electrically connected between the command interface and each channel switch QI, Q2. The switch controller controls the operation of each channel switch in order to control the operation of the LED channel(s) 221, 222 - i.e., to control which, if any, channels draw power from the driving signal D. In particular, the switch controller is able to selectively activate or deactivate each channel switch. The control of the channels switch(es) is performed responsive to the command signal Sc received at the command interface.

The switch controller 130 may be configured to cycle through different lighting states by controlling LED channels (if any) draw power via the control signals Sci, Sc2. For instance, the controller may cycle through the following sequence: a first LED channel 221 drawing power; a second LED channel 222 drawing power; and both LED channels drawing power. The cycling through each lighting state may, for instance, be responsive to an interruption in the mains power supply VAC and/or the DC power VDC. The interruption may be indicated by the command signal Sc.

The LED lighting arrangement further comprises a sensing circuit 240 electrically connected with the one or more LED channels. The sensing circuit 240 is configured to sense an electrical parameter of electricity (e.g., current or voltage drop) drawn by the one or more LEDs channels. As previously mentioned, the electricity/power drawn by a LED channel results from the switch controller controlling the operation of the one or more channel switches. The sensing circuit produces a sense signal Ss based on the sensed electrical parameter. What is to be noted is that the sense signal Ss is not the command signal Sc or the control signals Sci, Sc2.

The LED lighting arrangement further comprises a power converter controller 245. The power converter controller 245 is electrically connected to the power converter and is configured to control the power converter 210. The power converter is decoupled from the command signal Sc, but is coupled to the sense signal Ss. The power converter controller controls the output current as driving signal (e.g., regulates or varies the output current as driving signal) responsive to the sense signal Ss.

In this way, the power converter controller does not control the output current as driving signal D directly responsive to the command signal Sc, but rather responds to the effect of the command signal in changing which of the LED channel(s) draws power from the driving signal.

One working example of a configuration for the power converter controller to control the output current as driving signal is hereafter described. In this example, the switch controller is adapted to controllably permit or restrict current flow through each LED channel responsive to the command signal. In such a scenario, the sensing circuit may be configured to control the sense signal to have a first magnitude responsive to the switch controller permitting current flow through not all of the at least one LED channel; and a second, different magnitude responsive to the switch controller permitting current flow through all of the at least one LED channel. The power converter controller may be correspondingly adapted to regulate the output current as driving signal to have: a first level responsive to the sense signal having one of the first or second magnitude; and a second, different level responsive to the sense signal having the other of the first and second magnitudes.

Thus, the power converter controller is able to regulate the output current as driving signal to have different magnitudes based on the number of active LED channels, e.g., the amount of power demanded by the LED channels. This facilitates a responsive control of the output current as driving signal to changes in the desired lighting state of the LED channels. This responsive control can be more specific to the precise demand by the LED channel(s), e.g., rather than being an estimated or predicted demand. This facilitates more accurate and/or power efficient control over the operation of the LED lighting arrangement. Only when the LED channels has been successfully activated/deactivated, the power converter controller would adjust the output current as driving signal. This avoids failing or delaying in the channel switch QI or Q2 or failing in the LEDs of the LED channel.

In a more specific example, the power converter controller may regulate the output current as driving signal to have: a first current as the first level responsive to the switch controller permitting current flow through not all of at least one LED channel; and a second, larger current as the second level responsive to the switch controller permitting current flow through all of the one or more LED channels. Thus, more current may be made available to the LED channels if all of the LED channels are activated, compared to scenarios where fewer LED channels are activated.

It will be appreciated that the magnitude of the output current as driving signal D may increase responsive to more LED channels being activated (as indicated in the sense signal Ss) and reduce response with decreasing numbers of LED channels being activated. Thus, the more current demanded by, or required to drive the active LED channels, the greater the current provided to the LED channels by the power converter. This provides a user-friendly visual experience.

The proposed technique effectively provides a power converter controller that is able to react to changes in which LED channels are active, but does not make direct use of the command signal that brings about this change. The proposed approach is particularly advantageous as it permits or allows different reference voltages or grounds to exist in different parts of the circuit. In particular, an output of certain power converters will have a different ground (a “floating ground”) to a global ground. Example power converters that have this effect include buck converters, buck-boost converters and isolated converters. Thus, embodiments are particularly advantageous when the power converter 210 is or comprises a buck converter, a buck-boost converter and/or an isolated converter. An isolated converter may be formed of a transformer having a primary side galvanically connected to the power converter controller and a secondary side galvanically connected to the one or more LED channels.

The present disclosure advantageously avoids the need for a plurality of different power converters for different LED channels. This reduces the size of the circuitry for LED lighting arrangement, as well as being more efficient (e.g., as there will no longer be any idling of a power converter).

The LED lighting arrangement may comprise an input 290 configured to receive an input power signal. The power converter 210 is electrically connected to the input and is configured to convert the input power signal to produce the output current as driving signal.

The LED lighting arrangement may further comprise a command signal generator (not shown) electrically connected between the input and the command interface, the command signal generator being configured to generate the command signal responsive to any interruptions in the input power signal. Approaches for generating a command signal responsive to interruptions in the input power signal are known in the art, and are not described for the sake of conciseness. Figure 3 illustrates a portion of an LED lighting arrangement 200 according to an embodiment. For the purposes of illustrative clarity, the command interface and optional rectifying arrangement are not illustrated. Figure 3 illustrates one approach for embodying elements of the previously described LED lighting arrangement.

In particular, the power converter 210 is formatted as a buck converter, comprising a freewheeling diode D3, an inductor L, an electrolytic capacitor CE, a capacitor C (which may be omitted, but is preferred for filtering purposes) and a resistor R1 (which can similarly be omitted, but may be useful for filtering). The buck converter is connected to input power signal and the LED channel(s) 221, 222. The operation of the buck converter is controlled by the power converter controller 245, which provides the switching operation for the buck converter (e.g., via an internal switch/transistor such as an internal MOSFET). The structure of the buck converter corresponds to well-known circuit designs. Approaches for appropriately controlling a buck converter are also well established in the art.

The power drawn by the LED channel(s) 221, 222 is stored across the electrolytic capacitor CE. Thus, the two plates of the electrolytic capacitor effectively act as positive and negative terminals for the LED channel(s). The negative terminal of the electrolytic capacitor thereby acts as a ground FGND, which is floating compared to the true or real ground GND (which may be earthed). Thus, the ground FGND can be alternatively labelled a floating ground.

Thus, circuitry to one side of the buck converter is associated with a first reference voltage - the floating ground FGND, and circuitry to the other side is associated with a second reference voltage, the true ground GND.

Each channel switch is connected between the LED(s) of its respective LED channel and the floating ground FGND, rather than the real ground GND.

In particular, each channel switch may comprise a reference terminal electrically grounded to the first reference voltage, i.e., the floating ground FGND.

For improved efficiency of control of the channel switches, and to ensure appropriate bias voltages are provided, the switch controller 230 is also grounded to the first reference voltage, i.e., the floating ground FGND. Thus, the switch controller 230 may be electrically grounded to the first reference voltage FGND, such that the switch controller is able to directly drive each channel switch. Optionally, the switch controller is electrically connected to a control terminal of each channel switch, to provide direct driving of the channel switch(es) by the switch controller 230. Thus, there is hardly a need for a level shifting circuit or amplifying circuit between the switch controller 230 and the switches, and the present off-shelf SSW IC is applicable, i.e., can be used.

The power converter 210 and especially the power converter controller 245 may be both electrically connected to the second reference voltage, e.g., the real ground GND. This is advantageous for easy driving of the internal switch/transistor (e.g., MOSFET) of the power converter controller in operating the power converter 210.

The sensing circuit 240 may be adapted to sense a different value for the electrical parameter resulting from the switch controller differently controlling the operation of the one or more channel switches. In other words, the value of the sense signal Ss may change responsive to different operational control states of the one or more channel switches, such that the sense signal is able to indicate (with different values) the present operating/switched state of the LED channels.

In some examples, each channel switch is connected between a cathode of an LED of a respective channel and the first reference voltage; and the sensing circuit is electrically connected to each cathode to which each channel switch is connected. This provides a mechanism by which the sensing circuit is able to detect or monitor changes in the power flow through each channel, e.g., as it will be able to identify when no current or a floating voltage is present at the cathode of the LED (indicating no current flow and therefore no powering of the LED channel, or current or grounded voltage is present at the cathode of the LED (indicating the LED channel has been activated).

In preferred examples, the sensing circuit 240 comprises initial sensing circuitry 310. The initial sensing circuitry comprises, for each channel, a diode DI, D2 connecting the LED channel to a common node 311. The signal at the common node 311 acts as an initial sense signal Sis, in that it represents an initial form of the sense signal for controlling the power converter controller 245.

In the illustrated example, each diode connects a cathode of an LED in an LED channel (and therefore the collector of a channel switch) to the common node 311. However, this placement is not essential. By way of example, each diode may instead connect the emitter of a channel switch to the common node 311.

The common node 311 is here a central node of a voltage divider R3, R4. The voltage at the common node 311 will change responsive to the state of the LED channel(s). As the state of the LED channels will change responsive to which, if any, of the LED channels are permitted to drawn power from the driving signal D (as controlled via the switch(es) QI, Q2), the voltage at the common node 311 represents the lighting state of the LED lighting arrangement. More specifically, if all of the two channels are activated, two channel switches QI and Q2 are closed and the voltage at the node 311 is pulled low; if any of the two channels are deactivated, the voltage at the node 311 would be pulled high.

It will be appreciated that the configuration of the initial sensing circuitry 310 means that the value of the initial sense signal Sis is relative to the floating ground FGND, i.e., makes use of the floating ground as the reference point. This can cause problems with control performed by the power converter controller, as it (by design) is at the side of the buck converter associated with the true ground GND.

The present disclosure recognizes a desire to provide a mechanism for converting/shifting signals from the floating ground FGND reference point to the real ground GND reference point. In other words, there is a desire to decouple the power converter controller from the floating ground FGND reference point. Such decoupling will also decouple the power converter controller from the command signal. This advantageously means that the power converter controller reacts to the actual sensed state of the LED channel(s), e.g., the power demand, rather than a predicted power requirement noted by the command signal Sc or Sci and Sc2.

Even more, there is an advantage to delivering the sense signal Ss to the power converter controller while decoupling the power converter controller from the command signal Sc even in the absence of a floating ground (e.g., the invention is still applicable even if the power converter is instead a boost converter that does not provide a floating ground). However, it will be appreciated that embodiments are particularly advantageous to overcome any issues with floating grounds.

Two circuits are used together for level shifting and amplifying the sense signal to the power converter controller, and decoupling the power converter controller from the floating ground FGND and/or the command signal (Sc).

A first circuit for level shifting makes use of an isolation element 320. The isolation element 320 converts the initial sense signal Sis into a sense signal SDS, which uses the real ground GND as its reference point. The sense signal SDS may, in some embodiments, be treated also as the sense signal.

In the illustrated example, the isolation element 320 comprises an optocoupler. The optocoupler has a light emitting side electrically connected to the sensing circuit 240 and a light receiving side electrically connected to the power converter controller 245. In this way, the light emitting side of the optocoupler is electrically connected to the first reference potential; and the light receiving side of the optocoupler is electrically connected to the second reference potential.

The optocoupler is configured to receive the initial sense signal Sis (which uses the floating ground FGND as a reference point) and produce the sense signal SDS (which uses the real ground GND as its reference point). This is used for controlling the power converter controller 245.

Alternative forms of isolation elements 320 could be used according to other examples, e.g., a pair of magnetically coupled (but galvanically isolated) windings. An optocoupler is preferred for providing a more compact, materially efficient and low cost device.

A second circuit, switch component, 330 is used for amplifying or performing level shifting on the sense signal SDS. The switch component 330 can hereby act as a coupling buffer between the initial sense signal Sis and the power converter controller 245.

In the illustrated example, the switch component is configured to be driven by the sense signal SDS (here: via the isolation element 320) and to generate another sense signal Ss, e.g., a buffered sense signal. The power converter controller is electrically connected (e.g., at a sensing terminal CS) to the switch component 330 and configured to receive said sense signal. The power converter controller may regulate the output current as driving signal D (via the power controller 210) responsive to the switch signal.

The switch component 330 here comprises a buffer transistor Q3 that is controlled by the sense signal SDS (e.g., the initial sense signal Sis via the optocoupler). The buffer transistor Q3 is configured to provide a buffer between the isolation component 320 and/or the initial sensing circuitry 310 and the power converter controller 245. The switch component also comprises biasing resistors R5, R6, R7, R8, R9 that act to appropriately bias the buffer transistor and the signals to be provided to the power converter controller 245. Selection of appropriate values for these components will be apparent to the person skilled in the art. In some examples, these biasing resistors can be omitted, depending upon the requirements of the power converter controller.

In the illustrated example, the switch component is driven by the initial sense signal Sis via the optocoupler 320 or alternative isolation element. However, in other approaches, the isolation element 320 may be omitted, such that the switch component directly acts as an isolating element, e.g., in the form of a buffer transistor and/or level shifter. Thus, the isolation component 320 and optionally the switch component 330 provide approaches for level shifting and optional amplifying the sense signal from the LED channel to the power converter controller, and particularly decoupling the command signal SC, referencing the floating ground FGND, from the power converter controller.

Figure 4 illustrates a portion of a variant of the LED lighting arrangement 400 according to another embodiment. Unless otherwise identified, elements of the LED lighting arrangement 400 are similar or identical to previously described embodiments.

More particularly, figure 4 illustrates another approach for coupling the sense signal to the power converter controller, particularly effective for decoupling the command signal referencing the floating ground FGND from the power converter controller.

The initial sensing circuit 410 again comprises a diode DI, D2 connected between each LED channel and a common node 411. This drives an initial sense signal Sis, here: via a resistor R10.

The LED lighting arrangement comprise a switch component 420, which acts as a level shifter to effectively convert the initial sense signal Sis, which has a floating ground FGND reference point, to sense signal Ss that has a real/true ground GND reference point and is decoupled from the command signal.

In particular, the switch component 420 may comprise a low voltage transistor Q4 having a base connected to the sensing circuit 410, a collector connected to the driving signal D and an emitter connected to the first reference voltage FGND (e.g., the floating ground). In this configuration, the low voltage transistor is preferably a NPN transistor. However, the skilled person would be readily capable of modifying the switch component such that the low voltage transistor is a PNP transistor.

The switch component 420 may also comprise a high voltage transistor Q5 having a base connected to the collector of the low voltage transistor; an emitter connected to the driving signal D and a collector connected to the second reference voltage and the power converter controller, said high voltage transistor optionally being a PNP transistor.

The terms “low voltage transistor” and “high voltage transistor” have well established meanings in the art, as would be readily apparent to the skilled person. In particular, the maximum rating (e.g., for collector-base or collector-emitter voltage) for the low voltage transistor may be less than % of the same maximum rating for the high voltage transistor.

The precise values for the maximum ratings may be dependent upon the use case for the LED driving arrangement, e.g., the maximum expected voltage of the driving signal D. For instance, a low voltage transistor may have a maximum rating (e.g., for collector-base or collector-emitter voltage) of up to 25 V. A high voltage transistor may have a maximum rating (e.g., for collector-base or collector-emitter voltage) of over 25, e.g., over 50V, e.g., over 100V.

The high voltage transistor acts as the level shifter to effectively convert from the floating ground domain to the real ground domain. The high rating of the high voltage transistor provides robustness and reliability if the voltage difference between the floating ground and the real ground is high.

When only one of the two LED channels is activated, the voltage of the initial sense signal Sis is high, and turns on the transistor Q4. The transistor Q4 turns on the transistor Q5, and the transistor Q5 turns on the transistor Q6 to pull the signal Ss to the real ground GND. When both the two LED channels are activated, the voltage of the initial sense signal Sis is low, and turns off the transistor Q4. The transistor Q5 and the transistor Q6 are off, and the signal Ss is not pulled to the real ground GND.

Optionally, the transistor Q6 acts as a buffer transistor electrically connected between the collector of the high voltage transistor and the power converter controller 425. The buffer transistor Q6 may be omitted in some variations of the proposed approach.

Figure 5 illustrate an alternative configuration for the one or more LED channels 521, 522, corresponding one or more channel switches Q7, Q8 and corresponding initial sensing circuitry 510.

Rather than the LED channels being connected in parallel, the LED channels 521, 522 are connected in series. The channel switches Q7, Q8 are connected so as to selectively bypass the LED channels responsive to the control signals Sci, Sc2. Thus, when activated, a channel switch will bypass an LED channel to deactivate said LED channel. Approaches for modifying control procedures based on this understanding will be readily apparent to the skilled person.

The initial sensing circuitry 510 again comprises a diode D2 that connects to the cathode of the second LED channel LED2 to a node 511. It will be appreciated that, due to the inevitable voltage drops across the LED channels, the voltage at the common node 511 will change dependent upon which, if any, of the LED channels is/are conducting electricity. For example, if only one of the LED channels LED1 and LED2 is conducting, the voltage on the node 511 would be relatively high; if both LED channels are conducting, the voltage on the node 511 would relatively low. In this way, the voltage at the node 511 is able to act as an initial sense signal Sis that changes responsive to changes in which and/or how many of the LED channels 521, 522 are conducting electricity, i.e., are active. This provides useful information for controlling the output current as driving signal D provided to drive the active LED channels.

In the illustrated example, the initial sensing circuitry 510 comprises a voltage divider R3, R4, which acts in a similar manner to that previously described.

Optional resistor R14 help provide a non-zero value for the sense signal when no LED channel conducts electricity, for improved accuracy in sensing.

Figure 5 demonstrates how alternative LED channel arrangements and configurations can be used with the herein proposed approach, and that previously described LED channel arrangements and configurations are not essential to achieving the underlying inventive concept.

Applications of embodiments of the invention include indoor lighting, outdoor lighting as well as automotive lighting in which a head or tail light used in automotive is designed as such.

Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

If the term “adapted to” is used in the claims or description, it is noted the term “adapted to” is intended to be equivalent to the term “configured to”. If the term “arrangement” is used in the claims or description, it is noted the term “arrangement” is intended to be equivalent to the term “system”, and vice versa.

Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. An LED lighting arrangement comprising: a power converter configured to supply a driving signal; one or more LED channels configured to receive the driving signal, each LED channel comprising one or more LEDs configured to generate light; one or more channel switches each of which electrically connected with a respective one of the one or more LED channels; a command interface configured to receive a command signal for controlling the one or more LED channels; a switch controller electrically connected between the command interface and each channel switch, the switch controller being configured to control the operation of each channel switch so as to selectively activate the one or more LED channels responsive to the command signal; a sensing circuit electrically connected with the one or more LED channels, and configured to sense an electrical parameter of electricity drawn by the one or more LEDs channels resulting from the switch controller controlling the operation of the one or more channel switches and produce a sense signal based the sensed electrical parameter; and a power converter controller coupled to the sense signal and electrically connected to the power converter, configured to control the power converter to supply a variable driving signal to the LED channels responsive to the sense signal, wherein said power converter controller is electrically unconnected to the command signal and adapted to control the power converter to supply the driving signal being: a first current responsive to the sense signal indicating the switch controller permitting current flow through not all of the one or more LED channels; and a second, larger current responsive to the sense signal indicating the switch controller permitting current flow through all of the one or more LED channels.

2. The LED lighting arrangement of claim 1, wherein the power converter comprises any one or more of: a buck converter; a buck-boost converter; and/or an isolated converter formed of a transformer having a primary side galvanically connected to the power converter controller and a secondary side galvanically connected to the one or more LED channels.

3. The LED lighting arrangement of any of claims 1 to 2, further comprising a switch component connected between the sensing circuit and the power converter controller, wherein: the switch component is configured to be driven by said sense signal and to generate a switch signal; and the power converter controller is electrically connected to the switch component and configured to receive said switch signal and regulate the driving signal according to the switch signal.

4. The LED lighting arrangement of any of claims 1 to 3, wherein said sensing circuit is adapted to sense a different value for the electrical parameter resulting from the switch controller differently controlling the operation of the one or more channel switches; and each channel switch comprises a reference terminal electrically grounded to a first reference voltage; the switch controller is electrically grounded to the first reference voltage, such that the switch controller is able to directly drive each channel switch, optionally the switch controller is electrically connected to a control terminal of each channel switch; and the power converter and the power converter controller are both electrically connected to a second reference voltage, the second reference voltage being different to the first reference voltage.

5. The LED lighting arrangement of claim 4, wherein: each channel switch is connected between a cathode of an LED of a respective channel and the first reference voltage; and the sensing circuit is electrically connected to each cathode to which each channel switch is connected.

6. The LED lighting arrangement of any of claims 4 to 5, comprising an optocoupler having a light emitting side electrically connected to the sensing circuit and a light receiving side electrically connected to the power converter controller.

7. The LED lighting arrangement of claim 6, wherein: the light emitting side of the optocoupler is electrically connected to the first reference potential; and the light receiving side of the optocoupler is electrically connected to the second reference potential.

8. The LED lighting arrangement of any of claims 4 to 7, wherein the switch component comprises: a low voltage transistor having a base connected to the sensing circuit, a collector connected to the driving signal and an emitter connected to the first reference voltage, said low voltage transistor optionally being a NPN transistor; and a high voltage transistor having a base connected to the collector of the low voltage transistor; an emitter connected to the driving signal and a collector connected to the second reference voltage and the power converter controller, said high voltage transistor optionally being a PNP transistor.

9. The LED lighting arrangement of claim 8, wherein the switch component further comprises a buffer transistor electrically connected between the collector of the high voltage transistor and the power converter controller.

10. The LED lighting arrangement of any of claims 1 to 9, comprising an input configured to receive an input power signal, wherein: the power converter is electrically connected to the input and is configured to convert the input power signal to produce the driving signal.

11. The LED lighting arrangement of claim 10, further comprising a command signal generator electrically connected between the input and the command interface, the command signal generator being configured to generate the command signal responsive to any interruptions in the input power signal.

12. The LED lighting arrangement of any of claims 1 to 11, wherein: the switch controller is adapted to controllably permit or prevent current flow through each LED channel responsive to the command signal by closing the switch or deactivating the switch; the sensing circuit is configured to control the sense signal to have: a first magnitude responsive to the switch controller permitting current flow through not all of the at least one LED channel; and a second, different magnitude responsive to the switch controller permitting current flow through all of the at least one LED channel; and the power converter controller is adapted to regulate the output current as driving signal to have: a first level responsive to the sense signal having one of the first or second magnitude; and a second, different level responsive to the sense signal having the other of the first and second magnitudes.

13. The LED lighting arrangement of claim 12, wherein the power converter controller regulates the driving signal to have: a first current as the first level responsive to the switch controller permitting current flow through not all of at least one LED channel; and a second, larger current as the second level responsive to the switch controller permitting current flow through all of the one or more LED channels.

14. The LED lighting arrangement of any of claims 1 to 13, wherein the one or more LED channels comprises a plurality of LED channels connected in parallel.

15. The LED lighting arrangement of claim 14, wherein the one or more channels switch comprises a different channel switch for each LED channel, such that each channel switch controls the current flow through a respective LED channel, and wherein the sensing circuit comprises a common node to provide an initial of the sense signal and, for each channel switch, a respective diode coupled between a collector or emitter of the channel switch and the common node.