LED drive configuration

Abstract

In an LED lighting circuit, a conversion circuit is connected between a first LED load and a second LED load, converting power flowing through the first LED load and applying the converted power to the second LED load to control power flowing through the second LED load. The first LED load and the second LED load are connected in parallel, and a bus voltage is greater than a forward voltage of the first LED load but less than a forward voltage of the second LED load.

Description

[Technical Field]

[0001] The present invention relates to the field of lighting, and in particular to a drive arrangement for use in a luminaire. [Background technology]

[0002] With the increasing use of artificial light, there is an increasing demand for lamps, such as lamps or light bulbs. In particular, there is an increasing demand for compact, power-efficient lamps that can be mass-produced using reduced material resources. Lamps typically include a plurality of light-emitting diodes (LEDs) and an LED driving arrangement for driving or powering the LEDs.

[0003] Due to their relatively high efficiency, such LED driving configurations typically include switched-mode power supplies (SMPSs). However, while SMPSs have extremely high efficiency, they come at a relatively large size and cost. There are many applications where a more compact LED driving configuration would be advantageous (e.g., for use in small lamps, such as those used in automotive interiors or to illuminate the inside of home appliances). The size and cost of a switched-mode power supply are usually positively correlated with the power of the switched-mode power supply (the higher the power, the greater the size and cost).

[0004] One alternative to SMPSs for use in LED driving configurations is a linear circuit or linear power supply. Linear circuits have the advantage of simple circuit design (no switches required) and relatively small size and / or material cost, which increases ease of manufacturing. However, a disadvantage of existing linear circuits is that they typically have relatively low efficiency. Summary of the Invention [Problem to be solved by the invention]

[0005] It is therefore desirable to provide an LED driving arrangement that has increased efficiency while maintaining a compact size.

[0006] EP3099139A1 is a device that LED20 is connected to when the bus voltage V R 10. The topology disclosed includes a switching converter circuit 44 between the LEDs 22 and 23, and a separate LED 22 is powered by the switching converter circuit. [Means for solving the problem]

[0007] The invention is defined by the claims.

[0008] The proposed invention solves the above-mentioned problems by providing an LED lighting circuit that can adapt to different power requirements. In particular, today's LED lighting circuits often include two or more LED loads to achieve multiple color temperatures or multiple color light mixtures. Due to variances among the LED loads or different driving schemes for the LED loads, the LED loads are not driven identically, resulting in some degree of variation in the power to the LED loads. The present application proposes that the headroom when driving one LED load can be at least partially converted and used to drive or as headroom when driving another LED load. In this way, the headroom of one LED load is actively utilized rather than being fully dissipated in a passive and power-lossy manner. To achieve this, the present application proposes that a conversion circuit connected between the two LED loads is used to control the power flowing through one LED load using the power supplied to the other LED load.

[0009] In particular, it has been recognized that a large voltage gap between the output voltage of the primary power supply (for the LED load) and the forward voltage of the LED load will result in large losses in the overall LED lighting circuit if such a voltage gap is handled by a linear circuit.

[0010] The proposed system uses this significant voltage gap (much larger than the forward voltage of a single LED load) in an actively switched manner to supply energy to other nearby LED strings without dissipating a significant voltage tap with a linear switch. Thus, previously wasted energy is repurposed to power at least some of the other LED loads.

[0011] The described system thereby increases the efficiency of the LED lighting circuit while at the same time increasing the conduction time of the additionally powered LED load, thereby increasing LED utilization.

[0012] The above principle is particularly applicable to parallel LED strings, and more particularly to bus voltages that are above the forward voltage of one LED string but below the forward voltage of another LED string, thus reducing power loss when driving parallel LED strings.

[0013] According to an example according to an aspect of the present invention, there is provided an LED lighting circuit including: a primary power supply configured to output a primary output power to a bus such that the bus carries a bus voltage; a first LED load connected to the bus, the first LED load having a forward voltage lower than the bus voltage; and a second LED load connected to the bus, the second LED load having a forward voltage higher than the bus voltage; and an LED driving arrangement. an input, where a first LED load and the input are connected in series to a bus; an output, where a second LED load and the output are connected in series to the bus, the series connection of the second LED load and the output being in parallel with the series connection of the first LED load and the input; and a power conversion circuit connected between the input and the output, the power conversion circuit adapted to receive power flowing through the first LED load at the input, convert the power, and route the converted power to the second LED load via the output to control the power flowing through the second LED load.

[0014] The proposed approach allows for the control of power delivered through a second LED load using power previously passed through a first LED load, thus allowing for the reallocation of power to drive the second LED load in order to improve efficiency, consistency, and LED load utilization.

[0015] The power conversion circuit may be adapted to convert an input voltage received at the input into an output voltage at the output and to control the output voltage at the output, the output voltage being superimposed with power supplied to the second LED load by the bus and applied in a forward bias direction of the second LED load to regulate the power flowing through the second LED load.

[0016] This embodiment is suitable for injecting an extra voltage into the second LED load to drive the second LED load, which can relax the requirements on the amplitude of the bus voltage so that the bus voltage does not need to be too high (which may cause more power loss in the first LED load).

[0017] The power conversion circuit may be adapted to control an input voltage at an input of the power conversion circuit, the input voltage being adapted to be applied in a reverse bias direction of the first LED load to regulate power flowing through the first LED load and to offset power supplied to the first LED load by the bus.

[0018] This approach allows for control of the voltage across the first LED load to regulate the power flow through the first LED load, which can ensure more consistent and uniform operation of the LED lighting circuit (e.g., more consistent light output by the first LED load). It also provides headroom for driving the first LED load.

[0019] The power conversion circuit may be adapted, via the input, to control a voltage drop across the first LED load, which is the difference between the bus voltage and the input voltage, allowing regulation of power flow through the first LED load to improve consistency of light output by the first LED load.

[0020] The power conversion circuit may be adapted to control, via the input, a first residual voltage, which is the difference between the bus voltage and the voltage at the input, to approach a forward voltage of a first LED load, and to control, via the output, a second residual voltage, which includes the voltage at the output, to approach a forward voltage of a second LED load.

[0021] The residual voltage actively regulated by the power conversion circuit approaches the forward voltage of the LED load, thereby reducing the power loss for driving the LED load.

[0022] In some examples, the LED lighting circuit further includes a first linear current source connected between the first LED load, the input, and the bus, the first linear current source having a first minimum voltage headroom, and a second linear current source connected between the second LED load, the output, and the bus, the second linear current source having a second minimum voltage headroom.

[0023] In this example, the power conversion circuit can be implemented as a voltage regulator, and the current can be controlled relatively easily using a linear current source. Alternatively, the power conversion circuit can be implemented as a current regulator, and the extra current source can be omitted.

[0024] The power conversion circuit may be configured to control the voltage at the input such that a first voltage difference between the first residual voltage and the forward voltage of the first LED load is applied to a first linear current source and is greater than or equal to a first minimum voltage headroom but as close as possible to the first minimum voltage headroom, and to control the voltage at the output such that a second voltage difference between the second residual voltage and the forward voltage of the second LED load is applied to a second linear current source and is greater than or equal to the first minimum voltage headroom but as close as possible to the first minimum voltage headroom.

[0025] By providing a voltage difference higher than the minimum headroom across the linear current source, it is possible to ensure that the linear current source operates stably in linear mode and regulates the desired current.

[0026] The converter circuit may include an inverter circuit adapted to invert the polarity of power received at an input of the converter circuit to provide an inverted signal and to apply the inverted signal via the output to the second LED load in a forward bias direction to increase the voltage difference across the second LED load. This technique allows the voltage across the second LED load to be increased, for example, to exceed the forward voltage of the second LED load. This means that the second LED load can be driven to output light even when the bus voltage is not high enough to drive the second LED load by itself. Headroom for the second LED load is also provided.

[0027] In a further embodiment, the power supplied by the first LED load preferably balances with the power required by the second LED load.

[0028] In this embodiment, the power loss of the power conversion circuit is optimized. Alternatively, if the power supplied by the first LED load is significantly greater than the power required by the second LED load, the power conversion circuit may need to dissipate the excess power. This can be done by a power switch in the power conversion circuit or an extra linear switch in the power conversion circuit. In either case, since the second LED load is powered, the efficiency is improved compared to the prior art in which the second LED load is not powered at all.

[0029] In some examples, both the first LED load and the second LED load receive the same bus voltage.

[0030] This embodiment uses a single bus voltage to power both LED loads, which avoids using separate bus voltages and separate primary power converters for each LED load, reducing the complexity and cost of the lighting circuit.

[0031] The inverting circuit may be configured to apply an inverted signal via the output to the second LED load to control a voltage drop across the second LED load that is the sum of the output voltage and the bus voltage.

[0032] In some examples, the primary power supply is adapted to adjust the magnitude of the bus voltage so that it is higher than the forward voltage of the first LED load but lower than the forward voltage of the second LED load. The advantages of the proposed technique are particularly apparent when the bus voltage is insufficient to drive the second LED load by itself.

[0033] In this embodiment, the bus voltage can be selected as the midpoint between the two LED loads, allowing both LED loads to be driven reliably while reducing power loss.

[0034] The power conversion circuit may be configured to control the voltages across the first and second LED loads so that the voltage across the first LED load, which is the difference between the bus voltage and the input voltage, approaches the forward voltage of the first LED load, and / or so that the voltage across the second LED load, which is the sum of the bus voltage and the output voltage, approaches the forward voltage of the second LED load.

[0035] In this way, the headroom of both LED loads is reduced and power dissipation is also reduced.

[0036] In an alternative embodiment, the first LED load and the second LED load may be connected in series to the bus.

[0037] The primary power supply may be configured to supply a rectified version of the AC mains voltage as a bus voltage to first and second series-connected LED loads in a forward bias direction. The first and second LED loads may be driven by the rectified version of the AC mains voltage progressively and cumulatively, starting with the first LED load, as the rectified version of the AC mains voltage increases. This provides a technique for controlling the operation of the LED loads when driven by the AC mains voltage that can take into account fluctuations in the AC mains voltage. This is effectively a known tapped linear driving scheme in which the driven LED load depends on the amplitude of the AC mains supply, with the first LED load being driven directly by the AC mains supply in a first phase when the amplitude of the AC mains supply is only higher than the forward voltage of the first LED load, but the second LED load not being driven directly by the AC mains supply, and the series connection of the first and second LED loads being driven in a second phase when the amplitude of the AC mains supply is higher than the sum of the forward voltages of both the first and second LED loads. The forward voltage of the actually driven LED load closely matches the instantaneous amplitude of the AC mains supply so that headroom is regulated constantly low.

[0038] In some examples, the input of the conversion circuit is coupled to the cathode terminal of the first LED load and the output of the conversion circuit is coupled to the cathode terminal of the second LED load, and the power conversion circuit is configured to operate in an active mode when the bus voltage is greater than the forward voltage of the first LED load and less than the sum of the forward voltages of the first LED load and the second LED load, and when operating in the active mode, the inversion circuit is configured to apply an inverted signal to the second LED load via the output in a forward bias direction so as to increase the voltage across the second LED load to exceed the forward voltage of the second LED load.

[0039] This embodiment effectively utilizes the difference between the bus voltage and the forward voltage of the first LED load during the first phase to drive the second LED load. In comparison, in known tapped linear drivers, this difference during the first phase is dissipated by the linear switch, resulting in high power loss. Thus, the efficiency of this embodiment is high, the second LED load is driven for a longer duration, and the off-interval and flicker of the second LED load are reduced.

[0040] The power conversion circuit may be configured to operate in an inactive mode when the bus voltage is greater than the sum of the forward voltages of the first LED load and the second LED load, and when operating in the inactive mode, the power conversion circuit may be configured to disable power conversion. In this embodiment, once the AC mains power supply is able to directly drive both the first LED load and the second LED load, it should do so without the need to use the power conversion circuit. In this way, the switching losses of the power conversion circuit, which are already smaller than the power losses of a linear switch, can be prevented.

[0041] In a tapped linear driver, there may be three or more taps, and thus the concept of the above embodiment is not limited to only between the first and second LED loads, but can also be applied to the second tap / tap after the second LED load. More specifically, in some examples, the LED lighting circuit further includes: a third LED load connected in series with the first LED load and the second LED load, wherein the first LED load, the second LED load, and the third LED load are driven by the voltage bus progressively and cumulatively, starting with the first LED load, as the voltage of the voltage bus increases; a second conversion circuit, having a second input connected to the series connection of the first LED load and the second LED load without passing through the third LED load; a second output connected to the series connection of the first LED load, the second LED load, and the third LED load; and a second power conversion circuit connected between the second input and the second output, adapted to receive power flowing through the first LED load and the second LED load at the second input, convert the power, and send the converted power to the third LED load via the output to control the power flowing through the third LED load.

[0042] In this embodiment, when the voltage of the AC mains power supply is between the sum of the forward voltages of the first LED load and the second LED load and the sum of the forward voltages of the first LED load, the second LED load, and the third LED load, the voltage difference that would be dissipated in a known tapped linear driver is actively used / converted to drive the third LED load, thereby reducing power loss and reducing the non-operating interval and flicker of the third LED load.

[0043] The second power conversion circuit may be configured to operate in an active mode when the bus voltage is greater than the sum of the forward voltages of the first LED load and the second LED load and less than the sum of the forward voltages of the first LED load, the second LED load, and the third LED load, and the second power conversion circuit may include a second inverting circuit configured, when the second power conversion circuit operates in the active mode, to invert the polarity of power received at the second input to provide a second inverted signal, and to apply the second inverted signal in a forward bias direction to the third LED load via the second output so as to increase the voltage difference across the third LED load to exceed the forward voltage of the third LED load.

[0044] Preferably, the second inverter circuit is configured to operate in the inactive mode when the bus voltage is less than the sum of the forward voltages of the first LED load and the second LED load, and may be configured to operate in the inactive mode when the bus voltage is greater than the sum of the forward voltages of the first LED load, the second LED load, and the third LED load.

[0045] The second inverting circuit may disable application of the second inverted signal to the second output when operating in the inactive mode.

[0046] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. [Brief explanation of the drawings]

[0047] For a better understanding of the present invention, and to show more clearly how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: [Figure 1] 1 shows a schematic diagram of an LED lighting circuit according to a first embodiment; [Figure 2] 1 shows an example of an LED lighting circuit according to a first embodiment. [Figure 3]1 shows a switch mode power supply used in an embodiment. [Figure 4] 2 shows an LED lighting circuit according to a second embodiment. [Figure 5] 1 shows a conversion circuit used in an embodiment. [Figure 6] 10 shows a modified example of the LED lighting circuit according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0048] The present invention will now be described with reference to the drawings.

[0049] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the devices, systems, and methods, are 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 devices, systems, and methods of the present invention will become better understood from the following description, the appended claims, and the accompanying drawings. It should be understood that the drawings are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used to denote the same or similar parts throughout the drawings.

[0050] The present invention provides an LED lighting circuit, wherein a conversion circuit is connected between a first LED load and a second LED load, and controls power flowing through the second LED load by converting power flowing through the first LED load and applying the converted power to the second LED load.

[0051] In the context of this disclosure, when a voltage is applied to a (light-emitting) diode in a forward bias direction, the applied voltage is the voltage at the anode end of the diode (V AE ) and the voltage at the cathode end (V CE ) and the difference V DIF where V DF is V AE -V CE This increases the voltage difference in the forward bias direction.

[0052] Similarly, when a voltage is applied to a diode in the reverse bias direction, the applied voltage is equal to the voltage at the anode end of the diode (V AE ) and the voltage at the cathode end (V CE ) and the difference V DIF where V DF is V AE -V CE This reduces the voltage difference in the forward bias direction.

[0053] 1 is a schematic diagram of an LED lighting circuit 100 according to a first embodiment. The LED lighting circuit 100 includes a primary power source 110, a first LED load LED1, a second LED load LED2, and a conversion circuit 120.

[0054] Primary power supply 110 is configured to output primary output power on bus 115. This causes bus 115 to have a bus voltage V b The primary power source 110 may be formed from any suitable power circuitry, such as a rectifier, a PFC converter (including, for example, a rectifier, a buck converter, a boost converter, a buck-boost converter, etc.) for converting the main power source to a bus voltage, and / or a DC power supply system, including, for example, one or more batteries or cells.

[0055] Preferably, the LED lighting circuit 100 includes linear power supplies / current sources I1 and I2 for the first and second LED loads, respectively. This helps regulate the current through each LED load while maintaining a relatively small size and / or material cost. The linear current sources I1 and I2 can be realized by transistors, such as BJTs or MOSFETs, as are well known in the art.

[0056] A first LED load LED1 and a second LED load LED2 are both connected to a bus 115. In the illustrated example, the two LED loads LED1 and LED2 are connected in parallel to the bus, for example, both are directly connected to the bus. More specifically, for each LED load, the anode end of each LED load is connected to the bus such that primary output power can flow through the LED load when the voltage across the LED load exceeds the forward voltage of the LED load.

[0057] The conversion circuit 120 includes an input 121. The input 121 and the first LED load LED1 are connected in series to the bus 115. In the illustrated example, the input 121 is coupled to the cathode end of the first LED load LED1.

[0058] Conversion circuit 120 also includes output 122. The output and second LED load LED2 are connected in series to bus 115. In the illustrated example, output 122 is similarly coupled to the cathode end of second LED load LED2. It should also be noted that input 121 and output 122 could alternatively be located at the high / anode ends of the respective LED loads.

[0059] The conversion circuit 120 also includes a power conversion circuit 125 coupled between an input 121 and an output 122. The power conversion circuit is configured to receive power flowing through a first LED load LED1 via the input 121. The power conversion circuit 125 converts the received power and provides the converted power to a second LED load LED2 via the output 122. In this manner, the conversion circuit is configured to use the power flowing through the first LED load to control the flow of power through the second LED load.

[0060] In a simple example, power conversion circuit 125 may include or be an inverting circuit, such as an inverting switched-mode power supply, configured to invert the polarity of the voltage of the power received at input 121 and provide the inverted power at output 122. The inverted voltage may be provided to the cathode terminal of second LED load LED2 via output 122. This increases the voltage across second LED load LED2 to facilitate driving second LED load LED2, especially if the bus voltage is insufficient.

[0061] If the power conversion circuit does not have a step-down or step-up function, but only an inverting function, the voltage V at the output 122 of the power conversion circuit (and therefore at the cathode terminal of the first LED load LED1) o is the bus voltage Vb minus the forward voltage V of the first LED load LED1. F1 Thus, in this simple example, assuming no / negligible additional losses during inversion, V across the second LED load LED2 is approximately equal to LED2 teeth, TIFF2026504573000002.tif2245(1) can be estimated by

[0062] Therefore, the use of an inverting circuit reduces the bus voltage V b It is intuitively clear that this encourages driving the second LED load LED2, which has a larger forward voltage than

[0063] In this manner, the power conversion circuit 125 converts the input voltage (V B -V F1 ) at output 122 (V F1 -V B ) and the output 122 is adapted to convert the output voltage to bus V bThe output 122 is positioned / positioned to be effectively superimposed with the power supplied to the second LED load LED2 by the output 122. In particular, the output 122 is electrically coupled to the cathode terminal of the second LED load LED2, i.e., electrically downstream of the second LED load LED2. In this manner, the output 122 is connected such that the voltage supplied at the output 122 is applied in a forward bias direction to the second LED load LED2.

[0064] This allows the power conversion circuit 125 to adjust the power through the second LED load, for example using an inverting circuit. Preferably, the residual voltage (which is the sum of the bus voltage and the output voltage) should be close to the forward voltage of the second LED load so that power losses are low.

[0065] Furthermore, an optional linear current source I2 serves to regulate the current through the second LED load LED2. In instances where a linear current source is present, it is preferable that the voltage drop across the linear current source I2, which is the difference between the residual voltage and the forward voltage of the second LED load, exceeds the minimum headroom of the linear current source I2 and is as close as possible to the minimum headroom. In this way, the linear current source I2 can operate stably with as little power loss as possible. Here, "as close as possible" means that the residual voltage is no greater than the minimum headroom by more than a second safety margin value, such as less than 1 V.

[0066] Thus, the output voltage may be configured such that the voltage drop across the linear current source I2 is greater than the minimum headroom of the linear current source by a second safety margin, for example, 1V or less.

[0067] A similar principle can be applied to the first LED load: in this case, the residual voltage (which is the difference between the bus voltage and the input voltage) should be close to the forward voltage of the first LED load so that power losses are low.

[0068] In a variant, an optional linear current source I1 can be included to help regulate the current. Preferably, the voltage drop across the linear current source I1, which is the difference between the residual voltage and the forward voltage of the first LED load, exceeds the minimum headroom of the linear current source I1 and is as close as possible to the minimum headroom. In this way, the linear current source I1 can operate stably with as little power loss as possible. In this context, "as close as possible" means that the residual voltage is no greater than the minimum headroom by more than a first safety margin value, such as less than 1 V.

[0069] Thus, the input voltage may be controlled such that the voltage drop across the linear current source I2 is greater than the minimum headroom of the linear current source by a second safety margin, for example, 1V or less.

[0070] In one example, the power conversion circuit 125 may be adapted to control an input voltage at the input of the power conversion circuit. As shown in FIG. 1, this input voltage is applied in a reverse bias direction of the first LED load (i.e., controlling the input voltage reduces the voltage across the first LED load LED1 in a forward bias direction), thereby offsetting the power supplied to the first LED load by the bus. This facilitates regulating the power through the first LED load.

[0071] The same thing happens to the optional linear current source I1 in the first LED load. The voltage drop across the linear current source, which is the sum of the bus voltage minus the input voltage and the forward voltage of the first LED load, is as low as possible, close to the minimum headroom of the linear current source. Thus, the linear current source can operate with as little power loss as possible.

[0072] Therefore, the power conversion circuit may be adapted to control, via the input, a voltage drop across the first LED load and the linear current source (if present), which is the difference between the bus voltage and the input voltage.

[0073] Approaches to actively control the input voltage at the input are known to those skilled in the art, and typically involve controlling the effective impedance of the switching circuit, for example by modifying the duty cycle of the switching circuit.

[0074] In a plausible alternative to the LED lighting circuit 100 according to the first embodiment, the polarity of each LED load is reversed. The applied bus voltage may be negative to encourage current through each LED load. In this scenario, the input of the power conversion circuit may be connected to the cathode terminal of the first LED load, and the output may be connected to the anode terminal of the first LED load. Otherwise, operation may be similar / identical.

[0075] FIG. 2 shows an LED lighting circuit 100 according to a first embodiment with a more complex example of the conversion circuit 120 .

[0076] The conversion circuit 120 includes a switched-mode power supply 210. The switched-mode power supply is configured to convert power at the input 121 into converted power. Preferably, the switched-mode power supply includes a step-up or step-down transformer or converter. Examples of such circuits are well known in the art and include buck converters, boost converters, and / or buck-boost converters.

[0077] The conversion circuit 120 also includes an inverting circuit 220. The inverting circuit serves to invert the converted power provided by the power conversion circuit 210 and provide inverted power (in the form of an inverted signal) at the output 122.

[0078] In this manner, the inverting circuit 220 is adapted to invert the polarity of the power received (converted) at the input of the conversion circuit to provide an inverted signal, and to apply the inverted signal via the output to the second LED load in a forward bias direction so as to increase the voltage difference across the second LED load.

[0079] The illustrated inverting circuit 220 operates using switch-based logic to perform the inversion. As such, the inverting circuit 220 includes a number of switches S1, S2, S3, S4 and a number of capacitors that are operated / controlled to perform the inversion.

[0080] A first switch S1 controllably couples the input to the inverting circuit to a first plate of a first capacitor C1. A second switch S2 controllably couples the first plate of the first capacitor C1 to a reference voltage GND. A third switch S3 controllably couples a second plate (opposite the first plate) of the first capacitor C1 to the reference voltage GND. A fourth switch S4 controllably couples the second plate of the first capacitor C1 to an output node 122. The second capacitor couples the output node 122 to the reference voltage GND to smooth the voltage at the output node.

[0081] In general, a switch is switchable between an ON or "conducting state" (which allows current / power to flow) and an OFF or "blocking mode" (which allows no current / power to flow / negligible current / power to flow). Examples of suitable switches are well known to those skilled in the art and include FETs such as MOSFETs or other transistors.

[0082] To achieve inversion, the inversion circuit operates in alternating phases, i.e., sequentially alternating first and second phases (preferably of equal or approximately equal length). During the first phase, the first switch S1 and the third switch S3 are controlled to be in a conducting mode, and the second switch S2 and the fourth switch S4 are controlled to be in a blocking mode. During the second phase, the second switch S2 and the fourth switch S4 are controlled to be in a conducting mode, and the first switch S1 and the third switch S3 are controlled to be in a blocking mode.

[0083] Since inverter circuits are well known to those skilled in the art, the detailed control logic of inverter circuit 220 is not shown for clarity, but is easily understood and implemented by those skilled in the art.

[0084] In this way, the inverter circuit is controlled so that the voltage at the output of the inverter circuit is of opposite polarity (but equal magnitude) to the voltage at the input of the inverter circuit.

[0085] Other suitable examples of inverting circuits will be readily apparent to those skilled in the art.

[0086] For improved efficiency, the converter circuit 120 may further include a bypass switch SB, which can controllably bypass the connection between the second LED load LED2 and the output of the inverter circuit. This allows the bus voltage V b is advantageous to avoid the need to use the inverting circuit 220 (and / or the preceding elements of the conversion circuit) when the forward voltage of the second LED load exceeds the forward voltage of the second LED load.

[0087] In this manner, the conversion circuit 120 can be controlled to operate in an active mode, in which the inverting circuit provides an inverted signal to the output node (i.e., the conversion circuit provides negative voltage compensation), and in an inactive mode, in which the output of the inverting circuit is bypassed so that the second LED load LED2 is driven solely by power on the bus 115.

[0088] The conversion circuit 120 converts the voltage V b is the forward voltage V of the second LED load LED2 F2 If the voltage is less than V b <V F2 The conversion circuit 120 may be configured to operate in an active mode when the voltage at the voltage bus is equal to the forward voltage V of the second LED load LED2. F2 In or above V F2 ≦V b, it may be configured to operate in an inactive mode, which is useful when the primary power converter is a PFC converter whose output voltage is not 100% constant, but is a constant value component plus ripple / AC value component.

[0089] Further optional features of the conversion circuit 120 include a low dropout regulator (LDO) 230 (which regulates the voltage supplied to the inverter circuit 220), a third capacitor C3 (which smooths and stores the voltage output by the switched mode power supply 210), a diode D1, and a fourth capacitor C4 (which smooths and stores the voltage passed through the first LED load LED1).

[0090] It should be noted that the inverting circuit 220 shown in Figure 2 may be adapted for use as the power conversion circuit in the LED lighting circuit of Figure 1. Thus, the switched mode power supply 210 shown in Figure 2 may be omitted in some instances (with the inverting circuit acting as the power conversion circuit).

[0091] 2 is an auxiliary component 290. The auxiliary component may be any component of the LED lighting circuit (or nearby circuitry) that needs to be powered, such as a controller for the LED lighting circuit, e.g., an MCU, or a sensing component.

[0092] The conversion circuit 120 may be configured to generate power for the auxiliary component 290. In the illustrated example, this is accomplished by the auxiliary component drawing power from a switched-mode power supply 210 of the conversion circuit 120. In particular, the switched-mode power supply 210 includes a storage capacitor C that stores the power drawn by the auxiliary component. S This provides a complementary function to the conversion circuit 120.

[0093] Figure 3 shows an example of a switched mode power supply 210 for use in the conversion circuit described above. For better context, some of the peripheral circuitry is also shown.

[0094] The switched mode power supply includes a number of switches S5, S6, S7, S8 and capacitors C5, C6 for performing power conversion of a received signal (e.g., at input 121). In particular, the illustrated switched mode power supply is configured to perform step-up conversion such that the voltage at the output 212 of the switched mode power supply is greater (e.g., twice as great) than the voltage at the input of the switched mode power supply.

[0095] In some examples, capacitor C6 can be omitted and capacitor C3 may form part of switched mode power supply 210.

[0096] A fifth switch S5 controllably couples the input 211 to the switched-mode power supply to a first plate of a fifth capacitor C5. A sixth switch S6 controllably couples the input 211 to the switched-mode power supply to a second plate (opposite the first plate) of the fifth capacitor. A seventh switch S7 controllably couples the second plate of the fifth capacitor C5 to ground / reference voltage GND. An eighth switch S8 controllably couples the first plate of the fifth capacitor C5 to the output 212 of the switched-mode power supply.

[0097] The control of the switches S5, S6, S7, S8 of the switched mode power supply is carried out in the same phase as the control of the switches of the inverting circuit.

[0098] In particular, during the first phase, the fifth switch S5 and the seventh switch S7 are controlled to be in a conducting mode, and the sixth switch S6 and the eighth switch S8 are controlled to be in a blocking mode, and during the second phase, the sixth switch S6 and the eighth switch S8 are controlled to be in a conducting mode, and the fifth switch S5 and the seventh switch S7 are controlled to be in a blocking mode.

[0099] Thus, during the first phase, the fifth capacitor C5 is connected in parallel with the input 211 and is charged to the voltage at the input: V(C5) = V(211). During the second phase, the fifth capacitor is connected in series with the input 211 so that the voltage at the output 211 of the switched-mode power supply is the sum of the voltage at the input and the voltage across the fifth capacitor: V(212) = V(C5) + V(211). Because the voltage across the fifth capacitor is charged to equal the voltage at the input, this effectively charges the voltage at the output to twice the voltage at the input: V(212) = 2 * V(211). The sixth capacitor C6 provides a smoothing action to smooth out the effects of switching.

[0100] Although not required, in some examples, when the conversion circuit 120 is controlled to operate in an inactive mode, the switched-mode power supply is controlled such that the sixth switch and the seventh switch are controlled to be in a conducting mode (i.e., bypassing the rest of the conversion switched-mode power supply), which increases the efficiency of the overall LED lighting circuit.

[0101] It will be appreciated that the power conversion circuit of the first embodiment may be adapted to control the input voltage at the input of the power conversion circuit.

[0102] 3 illustrates a switched-mode power supply 210 that uses a switched capacitor converter. The advantage is its small / compact size. Alternatively, the switched-mode power supply 210 can be implemented with an inductor-based switched converter, such as a boost converter.

[0103] In the above embodiment, the first LED load and the second LED load are connected in parallel. This is not the only possible implementation.

[0104] 4 schematically illustrates an LED lighting circuit 400 according to a second embodiment. The LED lighting circuit 400 includes a primary power source 110, a first LED load LED1, a second LED load LED2, and a conversion circuit 420. The primary power source 110 may be a rectifier that rectifies an AC input voltage.

[0105] The main difference between the present LED lighting circuit 400 and the previously described LED lighting circuits is that the first LED load LED1 and the second LED load LED2 are connected in series (rather than in parallel). In this way, the first LED load LED1 and the second LED load LED2 are configured such that as the magnitude of the voltage bus increases, the number of LED loads driven by the voltage of the voltage bus increases progressively and cumulatively, starting with the first LED load LED1.

[0106] The conversion circuit includes an input 421 connected to the cathode terminal of the first LED load LED1 and ground, and an output connected to the cathode terminal of the second LED load LED2 and ground. Thus, the input is connected between the first LED load LED1 and the bus 115, and the output is connected between the second LED load LED2 and the bus 115.

[0107] The conversion circuit 420 also includes a power conversion circuit 425 coupled between an input 421 and an output 422. The power conversion circuit 425 is configured to receive power flowing through the first LED load LED1 via the input 421. The power conversion circuit 425 can convert the received power and provide the converted power to the second LED load LED2 via the output 422. In this manner, the conversion circuit is configured to use the power flowing through the first LED load to control the flow of power through the second LED load.

[0108] As with the first embodiment, in a simple example, the power conversion circuit 425 may include or be an inverting circuit, such as an inverting switched mode power supply, configured to invert the polarity of the voltage of the power received at input 421 and provide the inverted power at output 422. The inverted voltage may be provided to the cathode terminal of the second LED load LED2 via output 422. This increases the voltage across the second LED load LED2.

[0109] The voltage V at the input 421 of the power conversion circuit i is the bus voltage V b - forward voltage V of the first LED load LED1 F1 is approximately equal to:V i =V B -V F1 The voltage at the output, V o is the input voltage V i (i.e., reverse polarity), i.e., V o =-V i Thus, equation (1) can be applied to the simple example of the power conversion circuit of the second embodiment. In comparison, in a conventional tapped linear driver, the bus voltage V b and the forward voltage V of the first LED load LED1 F1 The difference is usually dissipated in a linear current source, causing power loss.

[0110] The power conversion circuit 425 may be deactivated in response to the bus voltage Vb exceeding the sum of the forward voltages of the first and second LED loads. Deactivating the power conversion circuit 425 may prevent the power conversion circuit 425 from converting and / or providing power at the input 421 to the output 422.

[0111] This can be achieved using an isolation switch SI connected in series with the power conversion circuit 425. The isolation switch may form part of the conversion circuit 420.

[0112] When the bus voltage Vb is large enough to be equal to or greater than the sum of the forward voltages of the first and second LED loads (i.e., V b ≧V F1 +V F2 If , the isolation switch can be controlled to be in a blocking mode that disconnects the power conversion circuit from input 421. Also, capacitor C7 can be bypassed by a switch (not shown). In this way, the primary output power (i.e., bus voltage) drives the first and second LED loads by itself, like a conventional tapped linear driver.

[0113] If the bus voltage Vb is not large enough to be less than the sum of the forward voltages of the first and second LED loads (i.e., V b <V F1 +V F2 , the isolation switch can be controlled to be in a conducting mode. In this way, the power conversion circuit is activated to provide converted power to the output 422 as described above (when current flows through the first LED load LED1).

[0114] In some cases, the bus voltage V b is the minimum voltage V min , the power conversion circuit 425 outputs at output 422 a voltage across the second LED load LED2 that is less than the forward voltage V of the second LED load LED2. F2 The output voltage V o For improved efficiency, the power conversion circuit 425 may be isolated in this scenario and / or may be bypassed (e.g., using a separate bypass switch (not shown)), or alternatively, the power conversion circuit 425 may even operate in a fully pass-through mode, connecting the first LED load LED1 to ground without conversion. min can be defined using the following formula: TIFF2026504573000003.tif1235(2).

[0115] Thus, in some examples, the power conversion circuitry may be configured to convert the bus voltage V b is the minimum voltage V min and the sum of the forward voltages of the first and second LED loads (i.e., V min ≦V b ≦V F1 +V F2 ) only when the output voltage V o is activated to provide

[0116] Suitable mechanisms for monitoring the voltage of a voltage bus and controlling the operation of the switches accordingly are well known in the art.

[0117] 5 shows an alternative conversion circuit 400 for use in the second embodiment. The conversion circuit 400 includes a switched mode power supply 510 (specifically, a buck converter) and an inverting circuit 520.

[0118] Generally, a switched mode power supply controls the magnitude of the voltage provided to output 422 , and an inverter circuit reverses or changes the polarity of the voltage to be opposite to the voltage at input 421 .

[0119] The switched-mode power supply includes input and output capacitors C8 and C9, a MOSFET M1, an inductor L, a freewheeling diode D2, and a resistor R1 (which may be omitted in some embodiments). Approaches to operating and controlling such switched-mode power supplies are well established in the art and will not be repeated for the sake of brevity. The switched-mode power supply is not limited to the structure shown, and any suitable configuration may be used instead. For example, a boost converter could be used instead.

[0120] In some examples, the switched-mode power supply is operated as an input constant current, output constant voltage converter. Resistor R1 may function as a sensing resistor. The input current is sensed using the sensing resistor and compared with a reference voltage. Based on the comparison result, the operation of MOSFET M1 may be controlled to perform input current constant control. Therefore, CCM control is adopted, and the average current can be determined by a given input current value.

[0121] By adjusting the switching duty cycle of M1, the effective input impedance of the switched mode power supply can be changed, and thus the voltage at the input, which is in series with the first LED load and the bus voltage, can be effectively adjusted to bring the residual voltage closer to the forward voltage of the first LED load, as described above.

[0122] The switching duty cycle of M1 also determines the desired voltage V at the output of the switched mode power supply. 510 These techniques are well known to those skilled in the art. 510 is the sum of the bus voltage and the output voltage, the residual voltage may be selected to be close to the forward voltage of the second LED load so that power loss is reduced.

[0123] Thus, in some instances, the voltage V 510 may be selected based on the following formula: TIFF2026504573000004.tif743(3).

[0124] Then, the voltage V 510 outputs an inverted signal V INV The voltage of the inverted signal is selected so that the voltage across the first and second LED loads is equal to or greater than the forward voltage of the first and second LED loads. 510If is chosen as defined in equation (3), the headroom is reduced.

[0125] In some examples, a linear current source I2 is connected in series with the second LED load (e.g., to control current flow as described above, e.g., to facilitate constant current drive). In this scenario, the headroom (e.g., voltage across) of the linear current source I2 is preferably greater than, but as close as possible to, the minimum headroom of the linear current source to maintain stable operation with minimal power loss. This improves the efficiency of the LED lighting circuit. As in the previous embodiment, a linear current source I1 is also provided to the first LED load LED1.

[0126] The voltage across the linear current source is the difference between the residual voltage and the forward voltage of the second LED load (i.e., V b +V o -V F1 ) In the example where a linear current source is present to facilitate constant current drive, the voltage V 510 may be selected based on the following formula: TIFF2026504573000005.tif854(4) where V minh is greater than, but as close as possible to, the minimum headroom of this linear current source to maintain stable operation with minimal power dissipation, where V minh The value of may be equal to the minimum headroom plus a safety margin value (e.g., minimum headroom + 1V).

[0127] Inverting circuit 520 includes a plurality of switches S9, S10, S11, S12 and capacitors C7, C10. The structure and operation of the inverting circuit may be identical to the inverting circuit described with reference to Figure 2 and will not be repeated for the sake of brevity.

[0128] It will be apparent that switched mode power supply 510 receives an input voltage at input 421 and performs a step-down function (e.g., a buck function) (such that it operates as a buck converter). The stepped-down voltage is inverted by inverting circuit 520 to produce an inverted signal at output 422.

[0129] With reference to Figure 4, we described how a conversion circuit can include an isolation switch. In the conversion circuit 400 shown in Figure 5, MOSFET M1 of the switched-mode power supply 510 may perform the function of the isolation switch (e.g., be held permanently in blocking mode when it is desired to isolate the conversion circuit). It will be appreciated that when the conversion circuit is in active mode, the control of MOSFET M1 follows a standard buck converter function (e.g., turning on and off according to a desired pattern to obtain a desired voltage output).

[0130] FIG. 6 shows a modified version of the LED lighting circuit 600 according to the second embodiment (described with reference to FIG. 4).

[0131] The LED lighting circuit 600 differs from the previously described LED lighting circuits in that it further includes a third LED load LED3, which is connected in series with the first LED load LED1 and the second LED load LED2.

[0132] The LED lighting circuit 600 also includes a second conversion circuit 620 .

[0133] The second conversion circuit 620 includes a second input 621 that is connected to the series connection of the first LED load LED1 and the second LED load LED2 without passing through the third LED load (i.e., not electrically downstream of the third LED load). Thus, the second input is connected at a point between the cathode terminal of the second LED load and the anode terminal of the third LED node, for example, connected to the cathode terminal of the second LED load.

[0134] The second conversion circuit 620 also includes a second output capacitor 622 connected to the series connection of the first, second, and third LED loads. Thus, the second output is connected electrically downstream of the third LED load LED3, for example, to the cathode terminal of the third LED load LED3.

[0135] The second conversion circuit 620 also includes a second power conversion circuit 625 connected between a second input 621 and a second output 623. The operation and structure of the second power conversion circuit 625 is similar to the operation of the power conversion circuit 425 and will not be repeated in detail for the sake of brevity.

[0136] Generally, the second power conversion circuit 625 is configured to receive power flowing through the first LED load and the second LED load at a second input, convert the power, and send the converted power to the third LED load via a second output to control the power flowing through the third LED load.

[0137] The second power conversion circuit 625 is preferably operable in an active mode and an inactive mode. When operating in the active mode, the power conversion circuit 625 provides converted power to the second output. When operating in the inactive mode, the power conversion circuit 625 does not provide converted power to the second output (e.g., the power conversion circuit is isolated and / or bypassed, for example, using the second isolation switch SI2).

[0138] Preferably, the second power conversion circuit includes a second inverting circuit configured to invert the polarity of the power received at the second input to provide a second inverted signal provided at the second output to increase the voltage difference across a third LED load (e.g., to drive the third LED load).

[0139] Thus, in a preferred example, the second power conversion circuit is configured to convert the bus voltage to a value greater than the sum of the forward voltages of the first and second LED loads, i.e., V b >V F1 +VF2 In some further examples, the second power conversion circuit operates in the active mode only when the bus voltage is greater than the sum of the forward voltages of the first LED load and the second LED load and less than the sum of the forward voltages of the first LED load, the second LED load, and the third LED load, i.e., V F1 +V F2 <V b ≦V F1 +V F2 +V F3 It operates in active mode only when

[0140] Otherwise, the second power conversion circuit may operate in an inactive mode, e.g., (preferably V b <V F1 +V F2 (preferably, V b >V F1 +V F2 +V F3 (In this case) it may be insulated.

[0141] Bus voltage V b is large enough so that it is equal to or greater than the sum of the forward voltages of the first, second, and third LED loads (i.e., V b ≧V F1 +V F2 +V F3 , the second isolation switch SI2 can be controlled to be in a blocking mode that disconnects the power conversion circuit from the second input 621. In this way, the primary output power (i.e., the bus voltage) drives the first, second, and third LED loads by itself.

[0142] Bus voltage V b is not large enough so that it is greater than the sum of the forward voltages of the first and second LED loads but less than the sum of the forward voltages of the first, second, and third LED loads (i.e., V F1 +V F2 <V b <V F1 +V F2 +V F3, the second isolation switch SI2 can be controlled to be in a conducting mode. In this way, the second power conversion circuit is activated to provide converted power to the second output 622 (when current flows through the first LED load LED1). A linear current source I3 is provided in series with the third LED load to regulate the current from the voltage provided by the second power conversion circuit.

[0143] In some cases, the bus voltage V b is the second minimum voltage V min2 If the voltage across the third LED load LED3 at the second output 622 is less than the forward voltage V of the third LED load LED3, the second power conversion circuit 625 F3 , the second power conversion circuit 625 may be isolated and / or bypassed (e.g., using a separate bypass switch (not shown)) to improve efficiency. min2 can be defined using the following formula: TIFF2026504573000006.tif1242(5).

[0144] Thus, in some examples, the second power conversion circuit may be configured to convert the bus voltage V b is the second minimum voltage V min2 and the sum of the forward voltages of the first, second, and third LED loads (i.e., V min2 ≦V b ≦V F1 +V F2 +V F3 ) only when the second output voltage V o is activated to provide

[0145] 6 illustrates further optional features of the LED lighting circuit 600. Among other things, the LED lighting circuit 600 may include further power conversion circuitry 675 and auxiliary components 680. The further power conversion circuitry may include power converters for driving or powering the auxiliary components, thereby allowing the further power conversion circuitry to use power carried by the bus 115 that would otherwise be unused by the LED load. This increases the efficiency of the overall LED lighting circuit 600 in that power wastage is reduced.

[0146] For example, the further power conversion circuit 675 may be a linear current source or a conventional SMPS converter (such as a buck) so that the further power conversion circuit supplies energy to the auxiliary components.

[0147] For example, auxiliary component 680 may be a controller or processor for an LED lighting circuit (eg, a component that controls the operation of a switch in the LED lighting circuit).

[0148] 4 and 6 show scenarios where different numbers of LED loads are connected in series and different numbers of converter circuits are used to control the flow of power through the different LED loads. More LED loads and corresponding converter circuits can be added. This can be generalized such that the concept of an LED lighting circuit is proposed that includes N LED loads (connected in series to a bus) and N-1 converter circuits.

[0149] Each ith converter is connected in parallel with the (i+1)th LED load. Each converter is connected to the voltage bus V b is the i-th minimum voltage V min(i) and the i-th maximum voltage V max(i) otherwise, the i-th conversion circuit may be configured to be activated (e.g., to provide an inverted signal at the corresponding output) only when the voltage V b is below the i-th minimum voltage) or (preferably, voltage Vb is greater than the i-th maximum voltage) may be isolated. min(i) and the i-th maximum voltage V max(i) The value of may be defined by the following formula: TIFF2026504573000007.tif1447(6) TIFF2026504573000008.tif1434(7) where V F(j) is the forward voltage of the jth LED load, and V F(i+1) is the forward voltage of the (i+1)th LED load.

[0150] This provides a fully controllable and configurable LED lighting circuit.

[0151] Variations to the disclosed embodiments can be understood by those skilled in the art, from a study of the drawings, the disclosure, and the appended claims, and can be implemented in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. The innovation can be used in interior and exterior lighting, as well as automotive lighting.

[0152] 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.

[0153] It should be noted that when the term "adapted to" is used in the claims or the specification, it is intended to be equivalent to the term "configured to." It should be noted that when the term "arrangement" is used in the claims or the specification, it is intended to be equivalent to the term "system," and vice versa.

[0154] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. a primary power source configured to output a primary output power to the bus such that the bus carries a bus voltage; a first LED load connected to the bus, the first LED load having a forward voltage lower than the bus voltage; a second LED load connected to the bus, the second LED load having a forward voltage higher than the bus voltage; An LED lighting circuit comprising: The LED driving arrangement includes a conversion circuit, the conversion circuit comprising: an input, wherein the first LED load and the input are connected in series to the bus; and an output, wherein the second LED load and the output are connected in series to the bus, the series connection of the second LED load and the output being in parallel with the series connection of the first LED load and the input; a power conversion circuit connected between the input and the output, receiving power at the input through the first LED load; converting the power; and sending the converted power to the second LED load via the output to control power through the second LED load; a power conversion circuit adapted to 1. An LED lighting circuit comprising:

2. The power conversion circuit includes: converting an input voltage received at the input to an output voltage at the output; and controlling an output voltage at the output, the output voltage being superimposed with power supplied by the bus to the second LED load and applied in a forward bias direction of the second LED load to regulate the power flowing through the second LED load; 10. The LED lighting circuit of claim 1, adapted to:

3. 3. The LED lighting circuit of claim 2, wherein the power conversion circuit is adapted to control an input voltage at the input, the input voltage being applied in a reverse bias direction of the first LED load to adjust power flowing through the first LED load and adapted to offset power supplied to the first LED load by the bus.

4. The power conversion circuit includes: controlling, via the input, a first residual voltage, which is the difference between the bus voltage and the voltage at the input, to approach the forward voltage of the first LED load; and controlling, via the output, a second residual voltage comprising a voltage at the output to approach a forward voltage of the second LED load; 10. The LED lighting circuit of claim 1, adapted to:

5. The LED lighting circuit is a first linear current source connected between the first LED load, the input, and the bus, the first linear current source having a first minimum voltage headroom; a second linear current source connected between the second LED load, the output, and the bus, the second linear current source having a second minimum voltage headroom; Including, The power conversion circuit includes: a first voltage difference between the first residual voltage and the forward voltage of the first LED load is applied to the first linear current source to control the voltage at the input to be equal to or greater than the first minimum voltage headroom, but as close as possible to the first minimum voltage headroom; and a second voltage difference between the second residual voltage and the forward voltage of the second LED load is applied to the second linear current source to control the voltage at the output to be equal to or greater than the first minimum voltage headroom but as close as possible to the first minimum voltage headroom; 5. The LED lighting circuit of claim 4, configured as follows:

6. The conversion circuit includes an inversion circuit, inverting the polarity of the power received at the input of the converter circuit to provide an inverted signal; and applying the inverted signal to the second LED load via the output in a forward bias direction so as to increase a voltage difference across the second LED load; It is adapted to 5. The LED lighting circuit of claim 4, wherein the power supplied by the first LED load is preferably balanced with the power required by the second LED load.

7. 5. The LED lighting circuit of claim 4, wherein the conversion circuit comprises a switched mode power supply connected between the input and an inverting circuit, the switched mode power supply adapted to step up or step down the voltage of power received at the input.

8. 10. The LED lighting circuit of claim 1, wherein both the first LED load and the second LED load are adapted to be powered by substantially the same bus voltage.

9. 9. The LED lighting circuit of claim 8, wherein an inverting circuit is configured to apply an inverted signal to the second LED load via the output to control a second residual voltage across the second LED load, the second residual voltage being the sum of the output voltage and the bus voltage.

10. 10. The LED lighting circuit of claim 8 or 9, wherein the primary power supply is adapted to adjust the magnitude of the bus voltage to be higher than a forward voltage of the first LED load but lower than a forward voltage of the second LED load.

11. A lighting fixture comprising an LED lighting circuit according to any one of claims 1 to 10.

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