Power demultiplexer for high-efficiency multi-channel LED drivers

Abstract

The present invention relates to a power stage for powering a first load, the first load being couplable between a first output and a second output, the power stage comprising: a first input for receiving a bus voltage; the first output coupled to the first input and configured to be couplable to the first load; a first capacitor coupled between the second output and a first further node and couplable in series with the first load; and a secondary power converter comprising: a controller for controlling the secondary power converter; a first inductive element and a first switching element coupled in series between the second input and a return node; a first unidirectional device coupled in series between the second output and the first further node, and a second inductive element inductively coupled to the first inductive element;

Description

[Technical Field]

[0001] The present invention relates to a power stage for supplying power to a load. The present invention further relates to a power supply system. [Background technology]

[0002] A power stage, often also called a driver, is used to regulate the power supplied to a load. A load may require a specific voltage to function properly. When a load or driver is replaced, it may be damaged or upgraded, and the load and driver may no longer be compatible with the supplied and required voltages. If the driver voltage is higher than the voltage required by the load, the voltage difference can result in additional losses. If the driver voltage is lower than the voltage required by the load, the load may not start or may not function properly.

[0003] In the field of lighting in particular, lighting loads can be replaced independently of their drivers. When a lighting load is replaced and a new combination of driver and lighting load is formed, the forward voltage of the lighting load may not exactly match the voltage supplied by the driver. This can lead to additional power loss in the driver or a malfunctioning combination of driver and lighting load. It is desirable that a greater degree of design freedom be provided by allowing a wider range of drivers to be combined with more types of lighting loads. [Overview of the project] [Problems that the invention aims to solve]

[0004] The object of the present invention is to provide a power-efficient device that enables, for example, the supply voltage from the driver to match the required voltage of the load. [Means for solving the problem]

[0005] To achieve this effect, a first embodiment of the present invention provides a power stage for supplying power to a first load, wherein the first load is coupled between a first output and a second output. - A first input for receiving the bus voltage, - The first output is coupled to the first input and configured to be coupled to the first load, - A first capacitor coupled between the second output and a further first node, and capable of being coupled in series with the first load, - It has a secondary power converter, and the secondary power converter is - A controller for controlling the secondary power converter, - A first inductive element and a first switching element are connected in series between the second input and the return node, - comprising a first unidirectional device coupled in series between the second output and the first further node, and a second inductive element inductively coupled to the first inductive element, The secondary power converter is configured to supply to the first capacitor a current that is of the opposite polarity to the current supplied to the first capacitor via the first load.

[0006] The power stage according to the present invention has a first input capable of receiving a bus voltage. The bus voltage can be any type of voltage, preferably a stable voltage. This voltage may have ripple such that the bus voltage is stable on average. A first output is provided, to which a first load can be connected. The first output is also coupled to the first input.

[0007] A first capacitor is provided between the second output and a first further node, and the first load can also be coupled to the second output. When the first load is coupled between the first output and the second output, the first load and the first capacitor are in series. A secondary power converter is provided. The secondary power converter has a controller used to control the secondary power converter. A first inductive element and a first switching element are coupled in series with each other and coupled between the second input and the return node. The first inductive element is inductively coupled to the second inductive element. A first unidirectional device is coupled in series between the second output and the first further node.

[0008] The secondary power converter is configured to supply to the first capacitor a current that is of the opposite polarity to the current supplied to the first capacitor via the first load.

[0009] The power stage according to the present invention makes it possible to match the voltage across the first load with the bus voltage. In this example, the sum of the voltages across the first load and the first capacitor is equal to the bus voltage. The voltage across the first load is not easily adjustable, but the voltage across the first capacitor can be adjusted by the secondary power converter. The secondary power converter uses the first switching element to allow current to flow through the first inductive element. The inductive coupling between the first inductive element and the second inductive element effectively causes the first and second inductive elements to form a flyback transformer. Therefore, the current flowing through the first inductive element is reflected in the second inductive element. The first unidirectional device is coupled to the second inductive element such that no current flows through the second inductive element when the first switching element is closed. Instead, when the first switching element is open, the current flowing through the first inductive element is reflected in the second inductive element, and therefore this current is used to supply the first capacitor with a current of opposite polarity to the current flowing through the first load. For example, the current flowing through the first load also flows through the first capacitor. This may be a current that discharges the first capacitor. The current supplied to the first capacitor through the second inductive element is of a polarity that charges the first capacitor. Balancing the charging and discharging of the first capacitor allows for adjustment of the voltage across the first capacitor, and therefore allows for adjustment of the current flowing through the first load. The duration of the on-time of the first switching element can be used to supply a controlled amount of energy to the first capacitor.

[0010] In a further example, the second input is directly coupled to the first input.

[0011] It is preferable to provide a direct coupling between the second input and the first input so that energy losses can be kept as low as possible. However, if necessary, electrical components may be placed between the second input and the first input, for example, to provide additional functionality.

[0012] In a further example, the first further node is connected to the return node.

[0013] Preferably, both the first capacitor and the series combination of the first inductive element and the first switching element are directly coupled to the return node. This allows for a simple and energy-efficient design of the power stage.

[0014] In a further example, the power stage further includes a linear current regulator in series between the first further node and the return node.

[0015] A linear current regulator may be provided between the first further node and the return node. In this case, the linear current regulator may be effectively connected in series with the first load and the first capacitor. The linear current regulator may be used to further reduce the current ripple of the current passing through the first load.

[0016] In a further example, the current supplied through the first load is configured to discharge the first capacitor.

[0017] In another example, the current supplied through the first load is configured to charge the first capacitor.

[0018] In a further example, the current supplied through the second inductive element is configured to charge the first capacitor.

[0019] In another example, the current supplied through the second inductive element is configured to discharge the first capacitor.

[0020] In a further example, the secondary power converter is a flyback converter.

[0021] Using a flyback converter for the secondary power converter enables an easy design of the inductive coupling between the first inductive element and the second inductive element.

[0022] In another example, a power supply system is provided. The power supply system includes - a power stage according to any of the previous examples, and - a third output coupled to the first input and configured to be coupled to a second load, wherein the second load is configurable to be coupled between the third output and a fourth output, - a second capacitor coupled between the fourth output and a second further node and configurable to be coupled in series with the second load, - and a tertiary power converter, wherein the tertiary power converter - includes a second unidirectional device, a third switching element, and a third inductive element inductively coupled to the first inductive element, which are serially coupled between the fourth output and the second further node, ? The secondary power converter further includes a second switching element in series with the first unidirectional device. The tertiary power converter is configured to supply a current to the second capacitor that has a reverse polarity to the current supplied to the second capacitor through the second load.

[0023] It should be noted that there may be an unclear part in the original text around line 21, marked with "?". Please check and correct if necessary.An additional second independent load may be powered by the same power supply system. The second load may be coupled in series with the second capacitor. A tertiary power supply may receive power from the first inductive element. The tertiary power supply has a second unidirectional device, a third switching element, and a third inductive element inductively coupled to the first inductive element, coupled in series between the fourth output and the second further node. The tertiary power supply may operate in the same way as the secondary power supply. The second unidirectional device allows the third inductive element to supply current to the second capacitor when the first switching element is open. Furthermore, the tertiary power converter is configured to supply a current to the second capacitor that is of the opposite polarity to the current supplied to the second capacitor through the second load. This means that if the current supplied through the load charges the capacitor, the current supplied by the third inductive element discharges the capacitor, and vice versa. The first inductive element supplies current to the second inductive element and the third inductive element. To determine the power distribution between the second inductive element and the third inductive element, the secondary power converter has a second switching element in series with the first unidirectional device, and the tertiary power converter has a third switching element in series with the second unidirectional device. Control of the second and third switches allows adjustment currents to flow to the first and second capacitors, respectively.

[0024] In another example, the power supply system includes a first load and a second load.

[0025] In another example, the first load and / or the second load are lighting loads.

[0026] Preferably, at least one of the loads is a lighting load. The other load may also be a lighting load, but it may also be another type of load, such as a sensor.

[0027] In another example, the lighting load is a semiconductor lighting load.

[0028] Examples of semiconductor lighting loads may include LEDs, laser diodes, or lasers such as vertical-cavity surface-emitting lasers (VCSELs).

[0029] In a further example, the forward voltage of the first load is different from the forward voltage of the second load.

[0030] The power supply system in the example makes it possible to compensate for the difference between the forward voltages of the load by supplying different voltages across the first capacitor and across the second capacitor.

[0031] In a further example, the power supply system further includes a mains power converter adapted to convert the mains power input voltage to the bus voltage.

[0032] The bus voltage may be an unregulated voltage, but preferably it is a regulated voltage. The main power converter can adjust an unregulated voltage, such as a rectified main power voltage, to a regulated bus voltage. [Brief explanation of the drawing]

[0033] Here, an example of the present invention will be described with reference to the attached drawings. [Figure 1] An example of a power stage circuit diagram is shown. [Figure 2] Here is another example of a power stage circuit diagram. [Figure 3] Here is another example of a power supply system circuit diagram. [Figure 4] Here is another example of a power supply system circuit diagram. [Figure 5] An example of a power supply system is shown. [Figure 6] Here is another example of a power supply system. [Modes for carrying out the invention]

[0034] The present invention will be described with reference to the figures.

[0035] The detailed descriptions and specific examples illustrate exemplary embodiments of the apparatus, systems, and methods, but are for illustrative purposes only and should not be understood as being intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems, and methods of the invention will be better understood from the following description, the appended claims, and the appended drawings. It should also be understood that the figures are for illustrative purposes only and are not drawn to scale. It should also be understood that throughout the figures, the same reference numerals are used to indicate the same or similar parts.

[0036] Figure 1 shows an example of a power stage. The power stage has a first input configured to receive a bus voltage. The power stage also has a ground node to provide a return path for the current supplied through the input. This node is shown as ground. In this example, it may also be called a return node or a first further node. In this example, a first inductive element L1 and a first switching element M1 are coupled in series between a second input 2, which is directly coupled to the first input 1, and the return node.

[0037] A first load LED1 and a first capacitor C1 are coupled in series between the first input and a first further node, which in this example is directly coupled to the return node. The first load LED1 may form part of the power stage. Thus, the power stage has a first output 1 and a second output 2 to which the first load LED1 is coupled. In this example, the first output 1 is directly coupled to the first input Input1. In this example, the second output 2 is directly coupled to the first capacitor C1 and the anode of the first unidirectional device D1. A first unidirectional device D1 and a second inductive element L2 are coupled in series between the second output 2 and a first further node. In this example, the secondary power converter has a first inductive element L1, a first switching element M1, a first unidirectional device D1, and a second inductive element L2. The first inductive element L1 and the second inductive element L2 are inductively coupled so that the secondary power converter forms a flyback converter. The secondary power converter may be controlled by a controller. The first capacitor C1 is considered a load for the secondary power converter. The secondary power converter supplies current to the first capacitor C1 in the positive polarity direction. The current flowing through the first load LED1 flows through the first capacitor C1 in the negative polarity direction. The insight of the present invention is that the voltage across the first load LED1 needs to be matched to the bus voltage so that the current through the first load LED1 can also be regulated. In this example, the bus voltage is lower than the voltage required by the first load LED1. The voltage across the first capacitor has a negative polarity compared to the voltage across the first load LED1, effectively "boosting" the bus voltage to the required load voltage. Therefore, the secondary power converter is used to raise the bus voltage level so that the voltage across the first load LED1 is large enough for the regulated desired current amplitude to flow through the first load LED1.

[0038] For example, the bus voltage may be 20V, and the voltage required for the first load LED1 may be 25V.

[0039] The bus voltage is equal to the sum of the voltage across the first load LED1 and the voltage across the first capacitor C1. In this case, the secondary power converter is controlled to generate a voltage across the first capacitor of -5V, and V bus =V load +V c This results in 20V = 25V - 5V.

[0040] To provide a more stable bus voltage, this bus voltage can be buffered by buffer capacitor C10. The bus voltage can have a fairly large double-line-frequency voltage ripple because the secondary power converter compensates for the ripple and keeps the load voltage constant.

[0041] Figure 2 shows an improved example of the power stage shown in Figure 1. The power stage has a first input Input1 configured to receive a bus voltage. The power stage also has a ground node to provide a return path for the current supplied through the input. This node is shown as ground. In this example, it may also be called a return node. In this example, a first inductive element L1 and a first switching element M1 are coupled in series between the second input Input2, which is directly coupled to the first input Input1, and the return node. A first load LED1 and a first capacitor C1 are coupled in series between the first input Input1 and a first further node. The first load LED1 may form part of the power stage. Thus, the power stage has a first output 1 and a second output 2, to which the first load LED1 is coupled. In this example, the first output 1 is directly coupled to the first input Input1. In this example, the second output 2 is directly coupled to the anode of the first capacitor C1 and the first unidirectional device D1. A first unidirectional device D1 and a second inductive element L2 are coupled in series between the second output 2 and the first further node. In this example, the secondary power converter has a first inductive element L1, a first switching element M1, a first unidirectional device D1, and a second inductive element L2. The first inductive element L1 and the second inductive element L2 are inductively coupled so that the secondary power converter forms a flyback converter. The secondary power converter can be controlled by a controller. A first capacitor C1 is considered a load for the secondary power converter. The secondary power converter supplies current to the first capacitor C1 in the positive polarity direction of the first capacitor C1. The current flowing through the first load LED1 flows through the first capacitor C1 in the negative polarity direction of the first capacitor C1. The insight of the present invention is that the voltage of the first load LED1 needs to be matched to the bus voltage so that the current through the first load LED1 can also be regulated. In this example, the bus voltage is lower than the voltage required by the first load LED1. The voltage across the first capacitor has a negative polarity compared to the voltage across the first load LED1, effectively "increasing" the bus voltage relative to the required load voltage.Therefore, the secondary power converter is used to increase the bus voltage level so that the voltage across the first load LED1 becomes large enough for the adjusted desired current amplitude to flow through the first load LED1.

[0042] For example, the bus voltage may be 20V, and the voltage required for the first load LED1 may be 25V.

[0043] The bus voltage is equal to the sum of the voltage across the first load LED1 and the voltage across the first capacitor C1. In this case, the secondary power converter is controlled to generate a voltage across the first capacitor of -5V, and V bus =V load +V c This results in 20V = 25V - 5V.

[0044] To provide a more stable bus voltage, this bus voltage can be buffered by a buffer capacitor C10. Additional circuitry is provided to reduce the ripple of the current flowing through the first load LED1. This is a linear current regulator. Transistor Q1 may be provided in series between the first further node and the return node, with a current sensing circuit R1. Feedback circuit 5 may receive a signal from the current sensing circuit R1 representing the current flowing through transistor Q1. In this example, the current sensing circuit R1 is a resistor. Feedback circuit 5 uses this signal to control the base of transistor Q1 so that a desired current flows through it. Feedback circuit 5 may also receive an additional signal to set a desired current amplitude. This may be a dimming signal, such as a PWM dimming signal, which may be supplied by a controller controlled by an external device such as a remote control device.

[0045] Note that the linear current regulator can be implemented not only in the example shown in Figure 2, but in any of the examples presented. Each capacitor in series with the corresponding load can also be coupled in series with the corresponding linear current regulator. In such cases, because the linear current regulator is placed in between, further nodes are not directly coupled to the return node.

[0046] Figure 3 shows an example of a power supply system. The power supply system may have a power stage according to an example of the present invention. The power supply system has a first input Input1 configured to receive a bus voltage. The power supply system also has a ground node to provide a return path for the current supplied through the input. This node is shown as ground. In this example, it may also be called a return node or a first further node. In this example, a first inductive element L1 and a first switching element M1 are coupled in series between a second input Input2, which is directly coupled to the first input Input1, and the return node. A first load LED1 and a first capacitor C1 are coupled in series between the first input Input1 and a first further node, which is directly coupled to the return node in this example. The first load LED1 may form part of the power supply system. Thus, the power supply system has a first output 1 and a second output 2, to which the first load LED1 is coupled. In this example, the first output 1 is directly coupled to the first input Input1. In this example, the second output 2 is directly coupled to the anode of the first capacitor C1 and the first unidirectional device D1. The first unidirectional device D1, the second switching element M2, and the second inductive element L2 are coupled in series between the second output 2 and the first further node. In this example, the secondary power converter has the first inductive element L1, the first switching element M1, the first unidirectional device D1, the second switching element M2, and the second inductive element L2.

[0047] A second load LED2 and a second capacitor C2 are connected in series between the first input Input1 and a second further node, which in this example is directly connected to the return node. The second load LED2 may form part of the power supply system. Thus, the power supply system has a third output 3 and a fourth output 4 to which the second load LED2 is connected. In this example, the third output 3 is directly connected to the first input Input1. In this example, the fourth output 4 is directly connected to the second capacitor C2 and the anode of the second unidirectional device D2. A second unidirectional device D2, a third switching element M3, and a third inductive element L3 are connected in series between the fourth output 4 and the second further node. In this example, the tertiary power converter has the second unidirectional device D2, the third switching element M3, and the third inductive element L3. A controller may also be used to control the tertiary power converter. This means that the controller may be used, for example, to control the third switching element M3. The first inductive element L1, the second inductive element L2, and the third inductive element are inductively coupled so that the secondary power converter forms a flyback converter. The main difference from a normal flyback converter is that switching elements are placed on the secondary and tertiary sides, i.e., on the sides of the second inductive element L2 and the third inductive element L3, to allow or prevent current from flowing to the corresponding first capacitor C1 or second capacitor C2. The current through the first inductive element L1 is reflected in the second inductive element L2 and the third inductive element L3. The second switching element M2 and the third switching element M3 can be controlled to control the current flowing from the second inductive element L2 and the third inductive element L3 to the first capacitor C1 and the second capacitor C2, respectively.

[0048] Similar to the examples shown in Figures 1 and 2, the current flowing through the load discharges the series capacitor, and the current supplied by the inductive element charges the capacitor. In this example, the current flowing through the first load LED1 discharges the first capacitor C1, and the current supplied by the second inductive element L2 charges the first capacitor C1. The current flowing through the second load LED2 discharges the second capacitor C2, and the current supplied by the third inductive element L3 charges the second capacitor C2. Similar to the examples in Figures 1 and 2, the voltages across the first capacitor C1 and the second capacitor C2 are negative, and the voltages required by the first load LED1 and the second load LED2 are greater than the bus voltage. By controlling the switching elements M1, M2, and M3, the voltages across the first capacitor C1 and the second capacitor C2 can also be controlled independently of each other. This makes it possible for the voltage required by the first load LED1 to be different from the voltage required by the second load LED2. The advantage in this situation is that a single bus voltage can supply multiple loads, even if the bus voltage does not match the load voltage.

[0049] Preferably, the first switching element M1, the second switching element M2, and the third switching element M3 are controlled by a single controller. To provide a more stable bus voltage, this bus voltage can be buffered by a buffer capacitor C10.

[0050] Figure 4 shows another example of a power supply system. This power supply system is substantially the same as the power supply system of Figure 3. The main difference is that the polarities of the first capacitor C1 and the second capacitor C2 are reversed. This means that the currents supplied by the second inductive element L2 and the third inductive element discharge the first capacitor C1 and the second capacitor C2, respectively. The currents flowing through the first load LED1 and the second load LED2 charge the first capacitor C1 and the second capacitor C2, respectively. In this example, the capacitor voltage can be positive. In that case, the bus voltage may be greater than the required load voltage.

[0051] As an example, considering only the first load LED1 for clarity, the bus voltage may be 25V, and the voltage required for the first load LED1 may be 20V.

[0052] The bus voltage is equal to the sum of the voltage of the first load LED1 and the voltage of the first capacitor C1. In that case, the secondary power converter is controlled to generate a voltage across the 5V first capacitor, and V bus =V load +V c results in 25V = 20V + 5V.

[0053] To provide a more stable bus voltage, this bus voltage can be buffered by a buffer capacitor C10.

[0054] Figure 5 shows another example of a power supply system. The power supply system has a first input Input1 configured to receive a bus voltage. The power supply system also has a ground node for providing a return path for the current supplied through the input Input. This node is shown as ground. In this example, it may also be called a return node or a first additional node.

[0055] In this example, the bus voltage is supplied by a mains power converter. The mains power converter may be configured to rectify the mains power input voltage. Typical mains power voltages are 230V at 50Hz or 120V at 60Hz. This rectified mains power voltage is converted to a bus voltage by the mains power converter. In this example, the mains power converter has an inductor L10, a switching element M10, and a unidirectional device D10, and is configured to operate as a boost converter. The mains power converter may be configured as any other type of switch-mode power converter, such as a boost converter, buck converter, buck boost converter, flyback converter, or LLC converter. The main purpose of the mains power converter is to convert the input voltage, in this case the mains power voltage, into a regulated bus voltage at input Input1.

[0056] In this example, a first inductive element L1 and a first switching element M1 are connected in series between the second input Input2, which is directly coupled to the first input Input1, and the return node. A first load LED1 and a first capacitor C1 are connected in series between the first input Input1 and a first further node, which is directly coupled to the return node in this example. The first load LED1 may form part of a power supply system. Therefore, the power supply system has a first output 1 and a second output 2 to which the first load LED1 is coupled. In this example, the first output 1 is directly coupled to the first input Input1. In this example, the second output 2 is directly coupled to the first capacitor C1 and the anode of the first unidirectional device D1. A first unidirectional device D1, a second switching element M2, and a second inductive element L2 are connected in series between the second output 2 and a first further node. In this example, the secondary power converter includes a first inductive element L1, a first switching element M1, a first unidirectional device D1, a second switching element M2, and a second inductive element L2.

[0057] A second load LED2 and a second capacitor C2 are connected in series between the first input Input1 and a second further node, which in this example is directly connected to the return node. The second load LED2 may form part of the power supply system. Thus, the power supply system has a third output 3 and a fourth output 4 to which the second load LED2 is connected. In this example, the third output 3 is directly connected to the first input Input1. In this example, the fourth output 4 is directly connected to the second capacitor C2 and the anode of the second unidirectional device D2. A second unidirectional device D2, a third switching element M3, and a third inductive element L3 are connected in series between the fourth output 4 and the second further node. In this example, the tertiary power converter has the second unidirectional device D2, the third switching element M3, and the third inductive element L3. A controller may also be used to control the tertiary power converter. This means that the controller may be used, for example, to control the third switching element M3. The first inductive element L1, the second inductive element L2, and the third inductive element are inductively coupled so that the secondary power converter forms a flyback converter. The main difference from a normal flyback converter is that switching elements are placed on the secondary and tertiary sides, i.e., on the sides of the second inductive element L2 and the third inductive element L3, to allow or prevent current from flowing to the corresponding first capacitor C1 or second capacitor C2. The current flowing through the first inductive element L1 is reflected in the second inductive element L2 and the third inductive element L3. The second switching element M2 and the third switching element M3 can be controlled to independently control the current flowing from the second inductive element L2 and the third inductive element L3 to the first capacitor C1 and the second capacitor C2, respectively.

[0058] Since a regulated bus voltage can be supplied by coupling a series combination of a first inductive element L1 and a first switching element M1 between the first input and the return node, the control of the first switching element M1 can be simplified. If the bus voltage is lower than the voltage supplied to the mains power converter, the components may have lower voltage requirements, allowing for the selection of smaller and / or less expensive components.

[0059] In this example, the mains power converter is paired with two loads. It should be understood that the mains power converter can be paired with any number of loads. For example, a power supply system for supplying power to a single load using the power stage shown in Figure 1 or 2 can also benefit from a mains power converter.

[0060] Figure 6 shows an example of another power supply system. This power supply system is almost identical to the power supply system in Figure 5. The same configuration is used to control the voltage across the first capacitor C1 and the voltage across the second capacitor C2. This power supply system differs from the power supply system in Figure 5 in that the series combination of the first inductive element L1 and the first switching element M1 is located at the second input Input2 and the return node. In the previous example, the second input Input2 was directly coupled to the first input Input1. In this example, the second input Input2 is coupled to the outputs of rectifiers D11, D12, D13 and D14. Therefore, the mains power converter does not need to provide the power conversion required by the second power converter, or the second power converter and the tertiary power converter. Instead, power can be taken directly from the mains power supply. This can result in more power-efficient power conversion for the power supply system.

[0061] The terms positive voltage and negative voltage are relative to ground, i.e., the return node. This means that the voltage across a capacitor can be considered positive or negative relative to ground.

[0062] In the examples shown, charging and discharging a capacitor can also be understood as supplying a positive or negative voltage to the capacitor. For example, if the average current supplied by the load is greater than the current supplied by the inductive element, the capacitor will effectively charge over time, and the voltage across the capacitor will increase and become positive. For example, if the average current supplied by the load is less than the current supplied by the inductive element, the capacitor will effectively discharge over time, and the voltage across the capacitor will decrease, and may even become negative.

[0063] In the example shown, one load may require a voltage higher than the bus voltage, while another load may require a voltage lower than the bus voltage. The polarity of the corresponding capacitors can be adjusted so that the higher and lower voltages can be matched to the bus voltage.

[0064] In the example shown, the switching element may be any type of semiconductor switch, such as a transistor and a MOSFET.

[0065] In the example shown, the inductive element may be a coil of a transformer. In a preferred example, a single transformer is used such that all the inductive elements for the secondary power converter, or for both the secondary and tertiary power converters, form a single inductor and are therefore all inductively coupled to one another.

[0066] In the examples shown, the unidirectional device may be, for example, a diode. A transistor can also be used, which is controlled to allow conduction in one direction and block conduction in the other direction.

[0067] A person skilled in the art will be able to understand and achieve, in carrying out the claimed invention, other variations of the disclosed embodiments by studying the drawings, specification and appended claims. In the claims, the word “has” does not exclude other elements or steps, and singular notation does not exclude plurality. The mere fact that certain means are listed in different dependent claims does not mean that combinations of these means cannot be used favorably. No reference numeral in the claims should be construed as limiting the scope.

Claims

1. A power stage for supplying power to a first load, wherein the first load can be coupled between a first output and a second output, and the power stage is The second output, the first further node, the second input, and the return node, A first input for receiving the bus voltage, The first output is coupled to the first input and configured to be coupled to the first load, A first capacitor coupled between the second output and the first further node, and capable of being coupled in series with the first load, It has a secondary power converter, and the secondary power converter is A controller for controlling the aforementioned secondary power converter, A first inductive element and a first switching element are coupled in series between the second input and the return node, The device comprises a first unidirectional device coupled in series between the second output and the first further node, and a second inductive element inductively coupled to the first inductive element, The secondary power converter is configured to supply to the first capacitor a current that is of the opposite polarity to the current supplied to the first capacitor via the first load.

2. The power stage according to claim 1, wherein the second input is directly coupled to the first input.

3. The power stage according to claim 1 or 2, wherein the first further node is coupled to the return node.

4. The power stage according to claim 1 or 2, further comprising a linear current regulator in series between the first further node and the return node.

5. The power stage according to claim 1 or 2, configured such that the current supplied via the first load discharges the first capacitor.

6. The power stage according to claim 1 or 2, configured such that the current supplied through the first load charges the first capacitor.

7. The power stage according to claim 1 or 2, configured such that the current supplied through the second inductive element charges the first capacitor.

8. The power stage according to claim 1 or 2, wherein the current supplied through the second inductive element is configured to discharge the first capacitor.

9. The power stage according to claim 1 or 2, wherein the secondary power converter is a flyback converter.

10. A power stage according to claim 1 or 2, A third output coupled to the first input and configured to be coupled to a second load, wherein the second load is coupled to a third output between the third output and a fourth output, A second capacitor is coupled between the fourth output and a second further node and can be coupled in series with the second load, A power supply system having a tertiary power converter, wherein the tertiary power converter is The fourth output and the second further node are coupled in series with a second unidirectional device, a third switching element, and a third inductive element inductively coupled to the first inductive element, The secondary power converter further comprises a second switching element in series with the first unidirectional device, A power supply system in which the tertiary power converter is configured to supply to the second capacitor a current that is of the opposite polarity to the current supplied to the second capacitor via the second load.

11. The power supply system according to claim 10, further comprising the first load and the second load.

12. The power supply system according to claim 10, wherein the first load and / or the second load is a lighting load.

13. The power supply system according to claim 12, wherein the lighting load is a semiconductor lighting load.

14. The power supply system according to claim 13, wherein the forward voltage of the first load is different from the forward voltage of the second load.

15. The power supply system according to claim 10, further comprising a main power converter adapted to convert a main power input voltage to the bus voltage.

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