SMPS series regulator for energy recirculation back to source

Abstract

The invention relates to a driver for supplying power to a first load. The driver comprises: a converter adapted to convert an alternating current (AC) voltage into a regulated voltage at an output of the converter, the regulated voltage referencing a reference; and a first load stage coupled to the output of the converter and adapted to receive the regulated voltage. The first load stage comprises: a first node adapted to receive the regulated voltage and adapted to be coupleable to a first load; a second node adapted to be coupleable to a first load such that the first load is coupleable between the first node and the second node; a first capacitor coupled between the second node and a reference; a first switched-mode power supply having a first input coupled to the second node and having a first output coupled to the first output node, where the first switched-mode power supply is adapted to regulate current through the first load.

Description

Technical Field

[0001] The present invention relates to a driver and also to a lighting system comprising the driver. Background Art

[0002] High power factor single stage drivers are commonly used in low cost products. When such drivers are used in lighting systems, the lighting loads connected to the driver may suffer from flicker and high frequency flicker visibility measurement SVM. To overcome this problem, another stage is introduced in the driver after the first stage. The first stage can be used to provide power factor correction PFC. As mentioned above, the output of the first stage is not conducive to providing high quality light output. The second stage receives the output of the first stage and regulates the current through the lighting load. The second stage can be designed in the form of a compact and inexpensive linear circuit. However, the linear circuit also introduces additional losses because the linear circuit dissipates the ripple that would otherwise exist across the lighting load. It is desirable to provide a technical solution that provides good reduction of flicker and SVM in an inexpensive manner while also reducing energy losses in the driver. Summary of the invention

[0003] It is an object of the present invention to provide a driver which is more energy efficient while still providing a well regulated current to the load.

[0004] In order to overcome this concern, in a first aspect of the present invention, a driver for supplying power to a first load is provided, the driver comprising:

[0005] a converter adapted to convert an alternating AC voltage into a regulated voltage at an output of the converter, the regulated voltage being referenced to a reference;

[0006] A first load stage, coupled to the output of the converter and adapted to receive the regulated voltage, the first load stage comprising:

[0007] a first node adapted to receive a regulated voltage and adapted to be coupleable to a first load;

[0008] a second node adapted to be couplable to the first load, such that the first load is couplable between the first node and the second node,

[0009] a first capacitor coupled between the second node and a reference;

[0010] A first switch mode power supply has a first input coupled to the second node and has a first output coupled to the first output node, wherein the first switch mode power supply is adapted to regulate current through a first load.

[0011] The driver has a converter that converts an input voltage into a regulated voltage. The input voltage may be a fluctuating voltage, such as an alternating AC mains voltage. Preferably, the regulated voltage is preferably a bus voltage that can be used to power another stage of the driver. The driver has a first load stage coupled to the output of the converter. The first load stage is therefore coupled to the bus voltage and therefore receives a regulated voltage from the converter. The load stage has a first node that receives the regulated voltage. A second node is provided. The first load to be powered by the driver is coupled between the first node and the second node. The first capacitor is coupled between the second node and the ground reference. The ground reference is preferably a reference used by the converter and the first load stage. As an example, the reference can be considered to be a ground reference. The first load and the first capacitor are coupled in series between the regulated voltage and the reference. The first load stage has a first switch mode power supply SMPS. The SMPS has a first input and a first output. The input is coupled to the second node. The first output is coupled to the first output node. The SMPS is also suitable for regulating the current through the first load.

[0012] The driver allows a good power factor to be achieved with the converter. The voltage provided by the converter is greater than the voltage required by the first load. The first capacitor is coupled in series with the first load, and therefore the regulated voltage is equal to the voltage across the load and the first capacitor. It is desirable to maintain the voltage constant as much as possible. For example, when the LED load is coupled to the first load stage, the voltage across the load will not fluctuate greatly. Therefore, for the LED load, it is desirable to regulate the current flowing through the LED load because this is directly related to the light output. The input terminal of the first SMPS can be effectively coupled in parallel with the first capacitor. Therefore, the voltage across the first capacitor is the voltage provided to the first input terminal of the first SMPS. The voltage across the first capacitor requires a certain voltage required for the operation of the first SMPS. If the voltage across the first capacitor is too low, the first SMPS cannot operate properly and cannot properly regulate the current through the first load. Therefore, the regulated voltage needs to be greater than the required first load voltage and the minimum required headroom voltage across the first capacitor (i.e., the first input terminal of the first SMPS). The first capacitor voltage can be provided to the converter so that the first SMPS can use the measured capacitor voltage as a feedback signal to change the amplitude of the regulated voltage if necessary. The voltage across the first capacitor can be regulated by a converter. The first SMPS is used to regulate the current through the first load. The energy obtained from the first capacitor is provided to the first output of the first SMPS. Here, the power can be used in different ways, as will be shown later. Since the first SMPS only needs to convert the voltage across the first capacitor (which is a relatively low voltage), the first SMPS can use smaller and cheaper components. Since the energy output by the first SMPS can be at least partially reused, the drive becomes more energy efficient.

[0013] In another example, the converter further includes a rectifier circuit adapted to convert the AC voltage into a rectified voltage.

[0014] Preferably, a rectifier circuit is provided between the AC voltage and the converter. Preferably, the rectifier circuit is a full bridge rectifier. The rectifier circuit allows the AC voltage, preferably the mains, to be rectified in an efficient manner.

[0015] In another example, the converter is any of a buck converter, a boost converter, a buck-boost converter, a flyback converter, or a resonant converter.

[0016] Preferably, the converter is any of a buck converter, a boost converter, a buck-boost converter, a flyback converter or a resonant converter. These types of converters allow very energy efficient conversion of an AC voltage to a regulated voltage. The rectifier circuit can also be easily integrated in any of these converters.

[0017] Preferably, the converter has a power factor correction function so that the input current waveform remains close to sinusoidal and in phase with the mains voltage.

[0018] In another example, the driver further includes a second load stage, the second load stage including:

[0019] a third node adapted to receive the regulated voltage and adapted to be coupleable to a second load;

[0020] a fourth node adapted to be couplable to a second load such that the second load is couplable between the third node and the fourth node,

[0021] a second capacitor coupled between the fourth node and a reference;

[0022] A second switched mode power supply has a second input coupled to the fourth node and has a second output coupled to the second output node, wherein the second switched mode power supply is adapted to regulate current through a second load.

[0023] Introducing a second load stage with the same layout as the first load stage will provide additional advantages. Multiple loads can be coupled to the regulated voltage. Preferably, the regulated voltage is provided on a single line such as a voltage bus. Now it is possible to power two loads in a more efficient manner. Another advantage is that the load voltages can be different from each other without affecting the overall efficiency. In the case where the first load stage and the second load stage are regulated by linear current regulators instead of using SMPS, both linear current regulators will dissipate too much power. In addition, in order for both linear current regulators to operate properly, the regulated voltage is equal to the maximum voltage of the two loads and the clearance required to operate the linear current regulator. The linear current regulator that regulates the current through the load with the lowest voltage has a higher clearance voltage and therefore has additional power losses. Using SMPS in the load stage makes the difference in load voltage almost insignificant. For the SMPS that regulates the current through the load with the lowest voltage, the input voltage of the SMPS will be larger. Since the SMPS does not operate in a dissipative manner, the efficiency of the SMPS is hardly affected by any changes on the input. When the output node is coupled back to the first node, the efficiency of the SMPS regulating the current through the load with the largest voltage will have slightly lower efficiency due to the larger voltage conversion ratio between the output and input of the SMPS than the SMPS regulating the current through the load with the lowest voltage. Since the throughput of the SMPS is only a fraction of the load power, the overall efficiency remains high.

[0024] In another example, the first output node is coupled to another load.

[0025] The first output load may be coupled to a further load. The load may be a load requiring a small amount of energy, such as a sensor, a wireless module or other circuit part of a driver, such as a VCC supply voltage to a converter and / or SMPS.

[0026] In another example, the first output node is further coupled to a voltage divider circuit.

[0027] It may be that the further load is not able to draw enough power to allow the current through the first load to be properly regulated. Therefore, a voltage divider circuit may be used alongside the further load so as to ensure that sufficient power is drawn at the first output node. Preferably, the voltage divider circuit has a controllable voltage divider so that the power dissipated by the voltage divider can be adjusted.

[0028] In another example, the first output node is coupled to the first node.

[0029] The first output node of the SMPS may be coupled to the first node. This allows the first SMPS to provide energy back to the load, i.e., to provide a regulated voltage back. This allows the power provided by the first SMPS to the first output node for regulating the current through the first load to be recycled back in an efficient manner.

[0030] In another example, the first switch mode power supply is a boost converter or a flyback converter, and / or wherein the second switch mode power supply is a boost converter or a flyback converter.

[0031] Preferably, the first SMPS and the second SMPS are boost converters or flyback converters or any combination thereof. The boost converter topology allows a simple and efficient up-conversion of the voltage across the capacitor to the voltage at the first output node. A flyback converter may provide an even more efficient up-conversion because the flyback has a transformer whose turns ratio may be adjusted to optimize the conversion.

[0032] In another example, a driver comprises a controller for controlling a first switched mode power supply, wherein the controller is arranged to control the switched mode power supply to regulate a current through a first load.

[0033] Preferably, the driver has a controller. The controller can be used to control the first SMPS so that the current through the first load is regulated. The controller can also be used to control the second SMPS to regulate the current through the second load. The controller can also be used to control the converter to control the regulated voltage.

[0034] In another example, the controller is part of the additional load.

[0035] The controller may be part of the further load.The first SMPS then not only regulates the current through the first load but also provides power for operating the controller.

[0036] In another example, a lighting system is provided, which has a driver according to any one of the above examples and a first load.

[0037] In another example, the first load is a semiconductor lighting load.

[0038] Preferably, the first load is a semiconductor lighting load. The semiconductor lighting load may be any one of a light emitting diode (LED), a laser diode or a laser load. Preferably, the second load is also a semiconductor lighting load. The semiconductor lighting load may also be any one of a LED, a laser diode or a laser load.

[0039] In another example, the lighting system includes a second load.

[0040] In another example, the second load is a non-lighting load.

[0041] The second load may be a non-lighting load, such as a sensor for detecting presence. A typical application of a lighting system in which the first load is a lighting load and the second load is a non-lighting load is a lighting system with, for example, presence detection. The driver is used to provide power to the lighting load, such as an LED lighting load, and also to provide power to a sensor for controlling the lighting load, such as a presence detector. This type of driver is also called a sensor-ready driver.

[0042] In another example, a required operating voltage of the first load is different from a required operating voltage of the second load.

[0043] A lighting system with a driver according to the foregoing example allows powering different loads with different required voltages from a single converter in an energy efficient manner. The voltage difference is compensated by the first SMPS and the second SMPS. With a linear current regulator, a voltage will exist across the linear current regulator, resulting in additional losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Examples of the present invention will now be described with reference to the accompanying drawings, in which:

[0045] Figure 1 An example of a driver according to the prior art is shown.

[0046] Figure 2 One example of a driver for driving a load in an efficient manner is shown.

[0047] Figure 3 Another example of a driver for driving a load in an efficient manner is shown.

[0048] Figure 4a and Figure 4b An example of a SMPS is shown.

[0049] Figure 5a and Figure 5b An example of a SMPS is shown.

[0050] Figure 6 Another example of a driver for driving a load in an efficient manner is shown. DETAILED DESCRIPTION

[0051] The present invention will be described with reference to the accompanying drawings.

[0052] It should be understood that the detailed description and specific examples, although indicating exemplary embodiments of the apparatus, system and method, are intended only for illustrative purposes and are not intended to limit the scope of the invention. These and other features, aspects and advantages of the apparatus, system and method of the present invention will become better understood from the following description, the appended claims and the accompanying drawings. It should also 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 throughout the drawings to indicate the same or similar parts.

[0053] Figure 1 An example of a driver according to the prior art is shown. Converter 1 is used to convert an alternating AC voltage into a regulated voltage. The regulated voltage is provided to a series circuit of a load LED and a linear current regulator 3. The regulated voltage is usually buffered by a buffer capacitor C. Controller 6 is used to sense the headroom across the linear current regulator 3. Controller 6 also uses a resistor R to sense the current flowing through the linear current regulator 3, and therefore also senses the current flowing through the load LED. The linear current regulator uses the sensed current to regulate the current through the load LED by controlling the gate of the linear switch M. The sensed headroom voltage is provided to converter 1 so that the regulated voltage amplitude matches the voltage required by the load and the headroom of the linear current regulator 3. For the headroom of the linear current regulator 3, it is understood as the voltage across the linear current regulator 3. This voltage cannot be too low, for example, it cannot be lower than 1V, because this causes the linear switch M to be unable to operate in its linear operating state. The headroom voltage needs to be maintained within the bandwidth. If the headroom voltage is too low, the linear current regulator 3 does not operate properly. If the headroom voltage is too high, the losses in the linear current regulator 3 will increase. Therefore, the controller 6 needs to provide a feedback signal to the converter 1 to allow the regulated voltage, and therefore the headroom voltage, to be regulated. Regardless of good headroom voltage control, the linear current regulator 3 will always be relatively lossy. This is especially true when there are multiple LED channels coupled to the same regulated voltage (each LED channel has a linear regulator). LED loads with lower voltages will result in a higher voltage across the linear regulator, and therefore more power dissipation. It is desirable to provide a technical solution that reduces power losses.

[0054] Figure 2 One example of a driver providing improved power efficiency is shown.

[0055] The driver has a converter 1 that converts an AC voltage into a regulated voltage Vreg. The AC voltage can be any AC type voltage and is preferably a mains voltage, where for example 230V at 50Hz and 120V at 60Hz are commonly used voltages. Preferably, the converter 1 performs power factor correction PFC on the AC voltage. An electromagnetic interference EMI filter 7 can be provided at the input of the converter 1.

[0056] Preferably, the regulated voltage Vreg is buffered by a buffer capacitor C5. The regulated voltage Vreg is provided to the first node Node1 of the first load stage 2. Therefore, the first node Node1 receives the regulated voltage Vreg. The first node Node1 is also coupled to the first load LED1. The first load stage 2 also has a second node Node2. The first load LED1 is also coupled to the second node Node2. Therefore, the first load LED1 is effectively coupled between the first node Node1 and the second node Node2.

[0057] Between the second node Node2 and a reference, a first capacitor C1 is placed. The reference is preferably a ground reference for the direct current DC part of the driver circuit.

[0058] The first load stage 2 has a first switch mode power supply SMPS 4. The second node Node2 is coupled to the first input terminal In1 of the first SMPS 4. The first SMPS 4 has an output terminal coupled to the first output node Out1. The first SMPS 4 is used to regulate the current through the first load LED1. The first capacitor C1 is effectively coupled at the input terminal of the first SMPS 4. The current through the first load LED1 can be regulated by sensing the current flowing through the first load LED1. This can be done by using a first current sensor RS1. The sensed current can be provided to the first SMPS 4 as a feedback signal. By controlling the current through the first load LED1, the voltage across the first capacitor C1 is automatically controlled. The voltage across the first capacitor C1 is actually the regulated voltage Vreg minus the voltage required by the first load LED1. This will represent the headroom voltage in the linear current regulator topology. Since there is no resistive path through which the load current will flow in the first load stage 2, no additional power loss is introduced. In fact, the capacitor C1 and the first SMPS 4 are used instead, providing an energy-efficient technical solution. In addition, since the first SMPS 4 converts only a portion of the total power represented by the voltage across the first capacitor C1, the first SMPS 4 can be designed as a very small SMPS. In the example provided, the first output node Out1 of the first SMPS 4 is coupled to the first node Node1, thereby effectively coupling the first output node Out1 of the first SMPS 4 to the regulated voltage Vreg.

[0059] In the example provided, the second load stage 3 is also coupled to a regulated voltage Vreg. The regulated voltage Vreg is provided to a third node Node3 of the second load stage 3. The third node Node3 is also coupled to the second load LED2. The second load stage 3 also has a fourth node Node4. The second load LED2 is also coupled to the fourth node Node4. Therefore, the second load LED2 is effectively coupled between the third node Node3 and the fourth node Node4.

[0060] Between the fourth node Node4 and a reference, a second capacitor C2 is placed. The reference is preferably a ground reference for the direct current DC part of the driver circuit, similar to the ground reference used with respect to the first load stage 2.

[0061] The second load stage 3 has a second switch mode power supply SMPS 5. The fourth node Node4 is coupled to the second input terminal In2 of the second SMPS 5. The second SMPS 5 has an output terminal coupled to the second output node Out2. The second SMPS 5 is used to regulate the current through the second load LED2. The second capacitor C2 is effectively coupled at the input terminal of the second SMPS 5. The current through the second load LED2 can be regulated by sensing the current flowing through the second load LED2. This can be done by using a second current sensor RS2. The sensed current can be provided to the second SMPS 5 as a feedback signal. By controlling the current through the second load LED2, the voltage across the second capacitor C2 is automatically controlled. The voltage across the second capacitor C2 is actually the regulated voltage Vreg minus the voltage required by the second load LED2. Since there is no resistive path through which the load current will flow in the first load stage 2, no additional power loss is introduced.

[0062] In the example provided, the second output node Out2 of the second SMPS 5 is coupled to the first third node Node3 , thereby effectively coupling the second output node Out2 of the second SMPS 5 to the regulated voltage Vreg.

[0063] It becomes clear from the description that the first load stage 2 and the second load stage 3 may be identical in design. However, it should be understood that these designs may differ from each other.

[0064] Combining the first load stage 2 with the second load stage 3 as described in the example allows the load voltages to be different from each other without seriously providing additional losses. Instead, the voltage across the first capacitor C1 and the voltage across the second capacitor C2 will be regulated to different voltage levels by the first SMPS 4 and the second SMPS 5, respectively.

[0065] Since the voltage across the first capacitor C1 and the voltage across the second capacitor C2 can be regulated independently and efficiently, the regulated voltage Vreg can be regulated in a simpler manner. The regulated voltage Vreg can be set at a fixed voltage high enough to provide voltage to the load requiring the maximum voltage. Therefore, the converter 1 only needs to regulate the regulated voltage Vreg to a single level.

[0066] Figure 3 Another example of a driver is shown. The driver may have Figure 2 The example converter 1 provided in the embodiment. The driver may also have Figure 2 . The first load stage 2 and the second load stage 3 of the example provided in FIG. The first output node Out1 of the first SMPS 4 and the second output node Out2 of the second SMPS 5 are not coupled to the regulated voltage Vreg. Instead, both of them are coupled to another load. The voltage at the first output node Node1 and the voltage at the second output node Node2 can be buffered by buffer capacitors C3 and C4, respectively, or by the same capacitor. The other load receives power from the first SMPS 4 via the first output node Out1 and receives power from the second SMPS 5 via the second output node Out2. The power drawn from the input terminals of the first SMPS 4 and the second SMPS 5 for regulating the current through the first load LED1 and the second load LED2, respectively, can be provided to the other load. In the case where the other load cannot consume all the power provided by the SMPS, an additional voltage divider can be introduced to dissipate the excess amount of power. The other load can be, for example, a sensor or any type of load that requires a significantly lower amount of power than the first load LED1 and / or the second load LED2. Preferably, the other load is a controller 6. The controller can be used to control the driver. The controller 6 may be used to control the first SMPS 4, the second SMPS 5 and the converter 1 or any combination thereof. The further load may also have a wireless communication module. The wireless communication module may provide the controller 6 with information about the amount of current to be provided to any of the loads.

[0067] In the example provided, both SMPSs provide power to the further load. It will be appreciated that only one SMPS may be required to provide power to the further load. The other SMPS may then be coupled to the regulated voltage Vreg.

[0068] It will also be appreciated that the second load stage 3 and the second load LED 2 are omitted. The first SMPS 4 may then be configured to provide power to the further load.

[0069] In the example provided, the first load LED1 and the second load LED2 are represented as light emitting diodes. The load may also be any other type of load requiring a regulated current or voltage. When the load is a lighting load, preferably a semiconductor lighting load, the load may be an LED, a laser diode or a laser load. When the load is a non-lighting load, the load may be, for example, a sensor for sensing presence or any environmental parameter, preferably a load requiring a constant current to operate.

[0070] Figure 4a An example of a first SMPS 4 is shown. In this example, the first SMPS 4 is designed as a boost converter. The boost converter has an inductor L1, a switch M1 and a diode D1, which are configured to provide a voltage greater than the voltage at the first input terminal In1 at the first output node Out1. The switch M1 is preferably controlled by a controller 6 to regulate the input voltage of the first SMPS 4. The switch M1 can be controlled by applying a pulse width modulated signal at the gate of the switch ML. The use of a boost converter can be particularly beneficial when the first output node Out1 is coupled to a regulated voltage Vreg that is always greater than the voltage at the input terminal of the first SMPS 4.

[0071] Figure 4b Another example of a first SMPS 4 is shown. In this example, the first SMPS 4 is designed as a flyback converter. The flyback converter has a transformer T2, wherein the primary winding of the transformer T2 is coupled to a switch M2. The switch M2 is also coupled to a ground reference. The transformer T2 has a secondary winding coupled to a first output node Out1 via a diode D2. The switch M2 can preferably be controlled by a controller 6 by applying a pulse width modulation signal at the gate of the switch M2. The turns ratio between the primary winding and the secondary winding of the transformer T2 can be used to optimize the transformation of the voltage at the first input terminal In1 to the voltage at the first output node Out1. Therefore, a larger voltage difference between the voltage at the first input terminal In1 and the voltage at the first output node Out1 can be transformed in a more energy efficient manner.

[0072] Figure 5aAn example of a second SMPS 5 is shown. In this example, the second SMPS 5 is designed as a boost converter. The boost converter has an inductor L3, a switch M3 and a diode D3, which are configured to provide a voltage greater than the voltage at the second input terminal In2 at the second output node Out2. The switch M3 is preferably controlled by a controller 6 to regulate the input voltage of the second SMPS 5. The switch M3 can be controlled by applying a pulse width modulated signal at the gate of the switch M3. The use of a boost converter can be particularly beneficial when the second output node Out2 is coupled to a regulated voltage Vreg that is always greater than the voltage at the input terminal of the second SMPS 5.

[0073] Figure 5b Another example of a second SMPS 5 is shown. In this example, the second SMPS 5 is designed as a flyback converter. The flyback converter has a transformer T4, wherein the primary winding of the transformer T4 is coupled to a switch M4. The switch M4 is also coupled to a ground reference. The transformer T4 has a secondary winding coupled to a second output node Out2 via a diode D4. The switch M4 can preferably be controlled by the controller 6 by applying a pulse width modulation signal at the gate of the switch M4. The turns ratio between the primary winding and the secondary winding of the transformer T4 can be used to optimize the transformation of the voltage at the second input terminal In2 to the voltage at the second output node Out2. Therefore, the larger voltage difference between the voltage at the second input terminal In2 and the voltage at the second output node Out2 can be transformed in a more energy efficient manner.

[0074] Figure 6 An example of another driver is shown. In this example, Figure 2 and Figure 3 Similar to the example provided in FIG. 1 , the converter 1 is used to convert the AC voltage into a regulated voltage Vreg. In this example, the first load stage 2 is similar to the example provided in FIG. Figure 3 The first load stage 2 is shown in FIG. The first SMPS 4 can be used to provide power to the controller 6. Alternatively, power can also be provided to the regulated voltage Vreg, i.e. the first node Node1. A linear current regulator 7 can be used instead of using a Figure 2 and Figure 3 The second load stage 5 is disclosed in the example shown in . In this example, it is expected that the voltage required by the second load LED2 is greater than the voltage required by the first load LED1 to provide the most energy efficient technical solution to at least the linear current regulator 7. In order to further optimize the efficiency, the controller 6 can be used to control the converter 1 to adjust the regulated voltage Vreg to a voltage level close to the voltage required by the second load LED2 plus the headroom voltage required by the linear current regulator 7.

[0075] In the example provided, the controller 6 may be used to control the first SMPS 4, the second SMPS 5. Furthermore, the controller 6 may also be used to provide control parameters or additional information to the converter 1.

[0076] Preferably, the driver is part of a lighting system. The lighting system may be a lamp or a retrofittable lamp. The lighting system may also have a first load LED1 and / or a second load LED2. Preferably, at least one of the loads is a lighting load, such as an LED load, a laser diode load or a laser load. One of the loads may also be a non-lighting load, thereby allowing the lamp to perform more functions than just providing general lighting. Preferably, if two or more loads are used, the load voltage required for each load may be different from the other required load voltages.

[0077] Other variations of the disclosed embodiments may be understood and effected by those skilled in the art in practicing the claimed invention by studying the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A driver for supplying power to a first load, the driver comprising: A converter (1) adapted to convert an alternating AC voltage into a regulated voltage (Vreg) at the output of said converter, said regulated voltage (Vreg) being referenced to a reference; a first load stage (2), coupled to the output of the converter and adapted to receive the regulated voltage (Vreg), the first load stage (2) comprising: a first node (Node1) adapted to receive said regulated voltage (Vreg) and adapted to be coupleable to said first load (LED1); a second node (Node2) adapted to be coupled to the first load (LED1), such that the first load (LED1) can be coupled between the first node (Node1) and the second node (Node2), a first capacitor (C1) coupled between the second node (Node2) and the reference; a first switched mode power supply (4) having a first input terminal (In1) coupled to the second node (Node2) and having a first output terminal coupled to a first output node (Out1), wherein the first switched mode power supply (4) is adapted to regulate a current through the first load (LED1), The first switch mode power supply (4) is a flyback converter.

2. The driver according to claim 1, wherein the converter (1) further comprises a rectifier circuit adapted to convert the AC voltage into a rectified voltage.

3. The driver according to any of the preceding claims, wherein the converter (1) is any of a buck converter, a boost converter, a buck-boost converter, a flyback converter or a resonant converter.

4. The driver according to any of the preceding claims, further comprising a second load stage (3), said second load stage comprising: a third node (Node3) adapted to receive the regulated voltage (Vreg) and adapted to be coupleable to a second load (LED2); a fourth node (Node4) adapted to be coupled to the second load (LED2), so that the second load (LED2) can be coupled between the third node (Node3) and the fourth node (Node4), a second capacitor (C2) coupled between the fourth node (Node4) and the reference; A second switched mode power supply (5) having a second input terminal (In2) coupled to the fourth node (Node4) and having a second output terminal coupled to a second output node (Out2), wherein the second switched mode power supply (5) is adapted to regulate a current through the second load (LED2).

5. Driver according to any of the preceding claims, wherein the first output node (Out1) is coupled to a further load.

6. The driver of claim 5, wherein the first output node (Out1) is further coupled to a voltage divider circuit.

7. The driver according to any one of claims 1 to 4, wherein the first output node (Out1) is coupled to the first node (Node1).

8. The driver according to claim 7, wherein the second switched mode power supply (5) is a boost converter or a flyback converter.

9. The driver according to any of the preceding claims, further comprising a controller (6) for controlling the first switched mode power supply (4), wherein the controller (6) is arranged to control the first switched mode power supply (4) to regulate a current through the first load (LED1).

10. A drive according to claim 9 when dependent on claim 5, wherein the controller (6) is part of the further load.

11. A lighting system comprising a driver according to any one of the preceding claims and comprising the first load (LED1).

12. The lighting system according to claim 11, wherein the first load (LED1) is a semiconductor lighting load.

13. The lighting system according to any one of claims 11 to 12, comprising the driver according to claim 5, and comprising the second load (LED2).

14. The lighting system according to claim 13, wherein the second load (LED2) is a non-lighting load.

15. The lighting system according to any one of claims 13 or 14, wherein a required operating voltage of the first load (LED1) is different from a required operating voltage of the second load (LED2).

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