SMPS series regulators that recycle energy back into the source

Abstract

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

Description

[Technical Field]

[0001] The present invention relates to a driver.The present invention further relates to a lighting system comprising said driver. [Background technology]

[0002] In low-cost products, single-stage drivers with high power factors are often used. When such drivers are used in lighting systems, the lighting load connected to the driver may suffer from flicker and high SVM (Stroboscopic Visibility Measure). To solve this problem, another stage is introduced after the first stage in the driver. The first stage may be used to provide power factor correction (PFC). The output of the first stage, as described above, is not good for providing high-quality light output. The second stage receives the output of the first stage and adjusts the current through the lighting load. The second stage may be designed in the form of a linear circuit, which is compact and inexpensive. However, the linear circuit also generates additional losses because it dissipates ripple that would otherwise be present across the lighting load. It is desirable to provide a solution that provides good reduction in flicker and SVM in an inexpensive manner while also reducing energy losses in the driver. Summary of the Invention [Problem to be solved by the invention]

[0003] It is an object of the present invention to provide a driver that is more energy efficient while providing a well-regulated current to the load. [Means for solving the problem]

[0004] To solve this problem, in a first aspect of the present invention, there is provided a driver for powering a first load, comprising: a converter adapted to convert an alternating current (AC) voltage into a regulated voltage referenced to a reference at an output of said converter; a first load stage coupled to the output of the converter and adapted to receive the regulated voltage, a first node adapted to receive the regulated voltage and adapted to be couplable to the first load; - 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; a first capacitor coupled between the second node and the reference; and a first load stage including a first switched mode power supply having a first input coupled to the second node and having a first output coupled to a first output node, the first switched mode power supply adapted to regulate current through the first load;

[0005] The driver includes a converter that converts an input voltage into a regulated voltage. The input voltage may be a variable voltage, such as an alternating current (AC) mains voltage. Preferably, the regulated voltage is a bus voltage that can be used to supply further stages of the driver. The driver includes 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 the regulated voltage from the converter. The first 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. A first capacitor is coupled between the second node and a ground reference. Preferably, the ground reference is a reference used by the converter and the first load stage. By way of example, the reference may be considered as 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 includes a first switched 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 a first output node, and the SMPS is further adapted to regulate a current through the first load.

[0006] The driver enables the converter to achieve a good power factor. The converter supplies a voltage greater than the voltage required by the first load. The first capacitor is coupled in series with the first load, so the regulated voltage is equal to the voltage across the load and the first capacitor. It is desirable to maintain the voltage as constant as possible. For example, if an LED load is coupled to the first load stage, the voltage across the load does not fluctuate much. Therefore, in the case of an LED load, it is desirable to regulate the current through the LED load, since this has a direct relationship to light output. The input of the first SMPS may effectively be coupled in parallel with the first capacitor. Therefore, the voltage across the first capacitor is the voltage supplied to the first input of the first SMPS. The voltage across the first capacitor requires some voltage for the first SMPS to operate. If the voltage across the first capacitor is too low, the first SMPS may not operate properly, and the current through the first load may not be properly regulated. 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 of the first SMPS. The first capacitor voltage can be supplied to the converter so that the first SMPS can change the amplitude of the regulated voltage as needed using the measured capacitor voltage as a feedback signal. The voltage across the first capacitor can be regulated by the converter. The first SMPS is used to regulate the current through the first load. Energy extracted from the first capacitor is supplied to the first output of the first SMPS. Here, the power can be used in various ways, as will be shown later. Because 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 less expensive components. Because the energy output by the first SMPS can be at least partially reused, the driver becomes more energy efficient.

[0007] In a further example, the converter further comprises a rectifier circuit adapted to convert the AC voltage into a rectified voltage.

[0008] 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 makes it possible to rectify the AC voltage, preferably the mains voltage, in an efficient manner.

[0009] In a further example, the converter is any of a buck converter, a boost converter, a buck-boost converter, a flyback converter, or a resonant converter.

[0010] Preferably, the converter is one of a buck converter, a boost converter, a buck-boost converter, a flyback converter, or a resonant converter. These types of converters allow for a very energy-efficient conversion of the AC voltage to the regulated voltage. A rectifier circuit can also be easily integrated into any of these converters.

[0011] Preferably, the converter has power factor correction so that the input current waveform remains close to sinusoidal and in phase with the mains voltage.

[0012] In a further example, the driver a third node adapted to receive the regulated voltage and adapted to be couplable to the second load; a fourth node, the fourth node adapted to be couplable to the second load such that the second load is couplable between the third node and the fourth node; a second capacitor coupled between the fourth node and the reference; and a second load stage including a second switched mode power supply having a second input coupled to the fourth node and having a second output coupled to a second output node, the second switched mode power supply adapted to regulate current through the second load.

[0013] Introducing a second load stage with the same layout as the first load stage provides additional advantages. Multiple loads can be coupled to the regulated voltage. Preferably, the regulated voltage is supplied through a single wire, e.g., a voltage bus. This allows two loads to be powered in a more efficient manner. Another advantage is that load voltages can differ from each other without affecting overall efficiency. In situations where the first and second load stages are regulated by linear current regulators instead of using SMPSs, both linear current regulators dissipate excess power. Furthermore, for both linear current regulators to operate properly, the regulated voltage is equal to the maximum voltage of both loads and the headroom required to operate the linear current regulators. The linear current regulator regulating the current through the load with the lowest voltage has a higher headroom voltage and therefore incurs additional power losses. The use of an SMPS in the load stage makes differences in load voltages nearly insignificant. In the case of the SMPS regulating the current through the load with the lowest voltage, the input voltage for that SMPS is larger. Because the SMPS does not operate in a dissipative manner, the efficiency of the SMPS is largely unaffected by any changes in the input. The efficiency of the SMPS regulating current through the load with the highest voltage is slightly lower when the output node is coupled back to the first node than the SMPS regulating current through the load with the lowest voltage because the voltage conversion ratio between the SMPS's output and input is greater. Because the SMPS handles only a small fraction of the load power, overall efficiency remains high.

[0014] In a further example, the first output node is coupled to a further load.

[0015] The first output node can be coupled to a further load, which may require a small amount of energy, such as a sensor, a wireless module, or other circuit parts of the driver, such as the VCC supply voltage to the converter and / or the SMPS.

[0016] In a further example, the first output node is further coupled to a bleeder circuit.

[0017] 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 bleeder circuit may be used next to the further load to ensure that sufficient power is drawn at the first output node. Preferably, the bleeder circuit has a controllable bleeder, so that the power dissipated by the bleeder can be regulated.

[0018] In a further example, the first output node is coupled to the first node.

[0019] The first output node of the SMPS can be coupled to the first node, which allows the first SMPS to return energy to the load, i.e., to the regulated voltage, allowing the power provided by the first SMPS to the first output node to regulate the current through the first load to be returned and reused in an efficient manner.

[0020] In a further example, the first switched-mode power supply is a boost converter or a flyback converter, and / or the second switched-mode power supply is a boost converter or a flyback converter.

[0021] Preferably, the first SMPS and the second SMPS are boost converters or flyback converters, or any combination thereof. A boost converter topology allows for simple and efficient up-transformation of the voltage across a capacitor to a voltage at the first output node. The flyback converter may provide even more efficient up-conversion because the flyback is a transformer whose turns ratio can be adjusted to optimize conversion.

[0022] In a further example, the driver comprises a controller for controlling the first switched-mode power supply, the controller being configured to control the first switched-mode power supply to regulate a current through the first load.

[0023] Preferably, the driver includes a controller that may be used to control the first SMPS so that the current through the first load is regulated, that may also be used to control the second SMPS to regulate the current through the second load, and that may also be used to control the converter to control the regulated voltage.

[0024] In a further example, the controller is part of the further load.

[0025] The controller may be part of the further load, in which case the first SMPS not only regulates the current through the first load but also provides power to operate the controller.

[0026] In another example, a lighting system is provided, the lighting system comprising a driver according to any of the previous examples and the first load.

[0027] In another example, the first load is a solid-state lighting load.

[0028] Preferably, the first load is a solid-state lighting load. The solid-state lighting load may be any of a light-emitting diode (LED), a laser diode, or a laser load. Preferably, the second load is also a solid-state lighting load. The solid-state lighting load may also be any of a light-emitting diode (LED), a laser diode, or a laser load.

[0029] In another example, the lighting system comprises the second load.

[0030] In another example, the second load is a non-lighting load.

[0031] 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, for example, a lighting system with presence detection. A driver is used to power a lighting load, for example, an LED lighting load, and also to power a sensor, for example, a presence detector, for controlling the lighting load. This type of driver is also called a sensor-enabled driver.

[0032] In another example, the required operating voltage of the first load is different from the required operating voltage of the second load.

[0033] A lighting system with a driver according to the previous example allows various loads with different voltage requirements to be powered by a single converter in an energy-efficient manner. The voltage difference is compensated for by the first SMPS and the second SMPS. In a linear current regulator, this voltage is present across the linear current regulator, resulting in additional losses. [Brief explanation of the drawings]

[0034] Examples of the invention will now be described with reference to the accompanying drawings, in which: [Figure 1] An example of a state-of-the-art driver is shown. [Figure 2]1 illustrates an example of a driver for driving a load in an efficient manner. [Figure 3] 2 shows another example of a driver for driving a load in an efficient manner. [Figure 4a] An example of an SMPS is shown below. [Figure 4b] An example of an SMPS is shown below. [Figure 5a] An example of an SMPS is shown below. [Figure 5b] An example of an SMPS is shown below. [Figure 6] 2 shows another example of a driver for driving a load in an efficient manner. DETAILED DESCRIPTION OF THE INVENTION

[0035] The present invention will be described with reference to the drawings.

[0036] 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, appended claims, and accompanying drawings. It should also be understood that the figures are schematic only and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the figures to indicate the same or similar parts.

[0037] FIG. 1 shows an example of a state-of-the-art driver. Converter 1 is used to convert an alternating current (AC) voltage into a regulated voltage. The regulated voltage is supplied to a series circuit of a load LED and a linear current regulator 3. The regulated voltage is typically buffered by a buffer capacitor C. Controller 6 is used to sense the headroom across linear current regulator 3. Using resistor R, controller 6 senses the current flowing through linear current regulator 3, and therefore the load LED. The linear current regulator uses the sensed current to regulate the current through the load LED by controlling the gate of linear switch M. The sensed headroom voltage is supplied to converter 1 to match the regulated voltage amplitude to the headroom of linear current regulator 3 and the voltage required for the load. The headroom of linear current regulator 3 is understood to be the voltage across linear current regulator 3. This voltage cannot be too low, e.g., below 1 V, because this would cause linear switch M to be unable to operate in its linear operating region. The headroom voltage needs to be maintained within a bandwidth. If the headroom voltage is too low, the linear current regulator 3 will not operate properly. If the headroom voltage is too high, losses in the linear current regulator 3 will increase. Therefore, the controller 6 needs to provide a feedback signal to the converter 1 to enable it to adjust the regulated voltage and therefore the headroom voltage. Despite good headroom voltage control, the linear current regulator 3 is always relatively lossy. This is especially true when there are multiple LED channels in the linear current regulator, each coupled to the same regulated voltage. An LED load with a lower voltage will result in a higher voltage across the linear regulator and therefore more power dissipation. It is desirable to provide a solution that reduces power losses.

[0038] FIG. 2 shows an example of a driver that provides improved power efficiency.

[0039] The driver comprises a converter 1 which converts an AC voltage into a regulated voltage Vreg. The AC voltage may be any AC type voltage, preferably a mains voltage, of which mains voltages, 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 may be provided at the input of the converter 1.

[0040] Preferably, the regulated voltage Vreg is buffered by a buffer capacitor C5. This regulated voltage Vreg is supplied to a 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 a first load LED1. The first load stage 2 further includes 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.

[0041] A first capacitor C1 is placed between the second node Node2 and a reference, which is preferably a ground reference used for the direct current (DC) portion of the driver circuit.

[0042] The first load stage 2 includes a first switched-mode power supply (SMPS) 4. The second node Node2 is coupled to a first input In1 of the first SMPS 4. The first SMPS 4 has an output coupled to a first output node Out1. The first SMPS 4 is used to regulate the current through the first load LED 1. A first capacitor C1 is effectively coupled to the input of the first SMPS 4. The current through the first load LED 1 can be regulated by sensing the current through the first load LED 1. This can be done using a first current sensor RS1. The sensed current can be provided as a feedback signal to the first SMPS 4. By controlling the current through the first load LED 1, the voltage across the first capacitor C1 is automatically controlled. The voltage across the first capacitor C1 is effectively the regulated voltage Vreg minus the voltage required for the first load LED 1. This represents the headroom voltage in a linear current regulator topology. Because the first load stage 2 does not have a resistive path through which the load current flows, no additional power loss is introduced. In effect, an energy-efficient solution is provided instead of using capacitor C1 and the first SMPS 4. Furthermore, because the first SMPS 4 converts only a small fraction 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 shown, the first output node Out1 of the first SMPS 4 is coupled to the first node Node1, which effectively couples the first output node Out1 of the first SMPS 4 to the regulated voltage Vreg.

[0043] In the example shown, the second load stage 3 is also coupled to the regulated voltage Vreg. The regulated voltage Vreg is supplied 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 further 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.

[0044] A second capacitor C2 is placed between the fourth node Node4 and a reference, which is preferably a ground reference used for the direct current (DC) portion of the driver circuit, similar to that used in the first load stage 2.

[0045] The second load stage 3 includes a second switched-mode power supply (SMPS) 5. The fourth node Node4 is coupled to a second input In2 of the second SMPS 5. The second SMPS 5 has an output coupled to a second output node Out2. The second SMPS 5 is used to regulate the current through the second load LED 2. A second capacitor C2 is effectively coupled to the input of the second SMPS 5. The current through the second load LED 2 can be regulated by sensing the current through the second load LED 2. This can be done using a second current sensor RS2. The sensed current can be provided as a feedback signal to the second SMPS 5. By controlling the current through the second load LED 2, the voltage across the second capacitor C2 is automatically controlled. The voltage across the second capacitor C2 is effectively the regulated voltage Vreg minus the voltage required for the second load LED 2. Because the first load stage 2 does not have a resistive path through which the load current flows, no additional power loss is introduced.

[0046] In the example shown, the second output node Out2 of the second SMPS 5 is coupled to the third node Node3, effectively coupling the second output node Out2 of the second SMPS 5 to the regulated voltage Vreg.

[0047] It will become apparent from this description that the first load stage 2 and the second load stage 3 may be identical in design, however, it should be understood that their designs may differ from each other.

[0048] As explained in the examples, combining the first load stage 2 and the second load stage 3 allows the load voltages to be different from each other without introducing significant additional losses. Instead, the voltage across the first capacitor C1 and the voltage across the second capacitor C2 are regulated to different voltage levels by the first SMPS 4 and the second SMPS 5, respectively.

[0049] Because the voltages across the first capacitor C1 and the second capacitor C2 can be efficiently regulated independently, the regulated voltage Vreg can be regulated in a simpler manner. The regulated voltage Vreg can be set to a fixed voltage high enough to supply the load with the greatest voltage demand. Therefore, the converter 1 only needs to regulate the regulated voltage Vreg to a single level.

[0050] FIG. 3 shows another example of a driver. The driver may include a converter 1 according to the example shown in FIG. 2. The driver may also include a first load stage 2 and a second load stage 3 according to the example shown in FIG. 2. 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, they are both coupled to an additional load. The voltage at the first output node Out1 and the voltage at the second output node Out2 may be buffered by buffer capacitors C3 and C4, respectively, or may be buffered by the same capacitor. The additional load receives power from the first SMPS 4 via the first output node Out1 and from the second SMPS 5 via the second output node Out2. Power drawn from the inputs of the first SMPS 4 and the second SMPS 5 to regulate the current through the first load LED1 and the current through the second load LED2, respectively, may be supplied to the additional load. In situations where the additional load cannot consume all of the power provided by the SMPS, an additional bleeder may be introduced to dissipate the excess power. The further load may be, for example, a sensor or any type of load that requires a significantly smaller amount of power than the first load LED 1 and / or the second load LED 2. Preferably, the further load is a controller 6. The controller may 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 regarding the amount of current that should be supplied to any of the loads.

[0051] In the example shown, both SMPSs power an additional load. It should be understood that only one SMPS may be required to power the additional load, in which case the other SMPS may be coupled to the regulated voltage Vreg.

[0052] It should also be understood that the second load stage 3 and the second load LED 2 may be omitted, in which case the first SMPS 4 may be configured to power the additional load.

[0053] In the illustrated example, the first load LED1 and the second load LED2 are represented as light-emitting diodes. The loads may also be any other type of load requiring a regulated current or voltage. If the load is a lighting load, preferably a semiconductor lighting load, the load may be an LED, a laser diode, or a laser load. If the load is a non-lighting load, the load may be, for example, a sensor for detecting the presence or any environmental parameter, preferably a load requiring a constant current to operate.

[0054] FIG. 4a shows an example of a first SMPS4. In this example, the first SMPS4 is designed as a boost converter. The boost converter includes an inductor L1, a switch M1, and a diode D1 configured to provide a voltage at a first output node Out1 that is greater than the voltage at a first input In1. The switch M1 is preferably controlled by a controller 6 to regulate the input voltage of the first SMPS4. The switch M1 may be controlled by applying a pulse-width modulated signal to the gate of the switch M1. The use of a boost converter may be particularly beneficial when the first output node Out1 is always coupled to a regulated voltage Vreg that is greater than the voltage at the input of the first SMPS4.

[0055] FIG. 4b shows another example of the first SMPS4. In this example, the first SMPS4 is designed as a flyback converter. The flyback converter includes a transformer T2, whose primary winding is coupled to a switch M2. The switch M2 is further 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 be controlled, preferably by the controller 6, by applying a pulse-width modulated signal to the gate of the switch M2. The turns ratio between the primary and secondary windings of the transformer T2 can be used to optimize the conversion of the voltage at the first input In1 to the voltage at the first output node Out1. Therefore, a larger voltage difference between the voltage at the first input In1 and the voltage at the first output node Out1 can be converted in a more energy-efficient manner.

[0056] FIG. 5a shows an example of a second SMPS 5. In this example, the second SMPS 5 is designed as a boost converter. The boost converter includes an inductor L3, a switch M3, and a diode D3 configured to provide a voltage at a second output node Out2 that is greater than the voltage at the second input In2. The switch M3 is preferably controlled by a controller 6 to regulate the input voltage of the second SMPS 5. The switch M3 may be controlled by applying a pulse-width modulated signal to the gate of the switch M3. The use of a boost converter may be particularly beneficial when the second output node Out2 is always coupled to a regulated voltage Vreg that is greater than the voltage at the input of the second SMPS 5.

[0057] FIG. 5b shows another example of the second SMPS5. In this example, the second SMPS5 is designed as a flyback converter. The flyback converter includes a transformer T4, whose primary winding is coupled to a switch M4. The switch M4 is further 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 be controlled, preferably by the controller 6, by applying a pulse-width modulated signal to the gate of the switch M4. The turns ratio between the primary and secondary windings of the transformer T4 can be used to optimize the conversion of the voltage at the second input In2 to the voltage at the second output node Out2. Therefore, a larger voltage difference between the voltage at the second input In2 and the voltage at the second output node Out2 can be converted in a more energy-efficient manner.

[0058] FIG. 6 shows another driver example. In this example, similar to the examples shown in FIGS. 2 and 3, converter 1 is used to convert an AC voltage to a regulated voltage Vreg. In this example, first load stage 2 is similar to the first load stage 2 shown in FIG. 3. A first SMPS 4 can be used to supply power to controller 6. In another example, power can be supplied to the regulated voltage Vreg, i.e., first node Node1. Instead of using second load stage 5 as disclosed in the examples shown in FIGS. 2 and 3, a linear current regulator 7 can be used. In this example, to provide the most energy-efficient solution for at least linear current regulator 7, it is desirable that the voltage required for second load LED 2 be greater than the voltage required for first load LED 1. To further optimize efficiency, controller 6 can be used to control converter 1 to regulate regulated voltage Vreg to a voltage level close to the voltage required for second load LED 2 plus the headroom voltage required for linear current regulator 7.

[0059] In the example shown, the controller 6 may be used to control the first SMPS 4 and the second SMPS 5. Furthermore, the controller 6 may also be used to provide the converter 1 with control parameters or additional information.

[0060] Preferably, the driver is part of a lighting system. The lighting system may be a luminaire or a retrofittable lamp. The lighting system may also have a first load LED1 and / or a second load LED2. Preferably, at least one load 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, allowing the luminaire to perform more functions than just providing general lighting. Preferably, if more than one load is used, the required load voltage for each load may be different from the required load voltages for the others.

[0061] Those skilled in the art can understand and effect other variations to the disclosed embodiments in practicing the claimed invention, from a study of the drawings, the specification and the appended claims. In the claims, the word "comprises" does not exclude other elements or steps, and the singular 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 interpreted as limiting the scope.

Claims

1. a driver for powering a first load, a converter adapted to convert an AC voltage into a regulated voltage referenced to a reference at an output of the converter; a first load stage coupled to the output of the converter and adapted to receive the regulated voltage; a first node adapted to receive the regulated voltage and adapted to be couplable to the first load; 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; a first capacitor coupled between the second node and the reference; and a first load stage including a first switched mode power supply having a first input coupled to the second node and having a first output coupled to a first output node, the first switched mode power supply adapted to regulate a current through the first load, the first switched mode power supply being a flyback converter.

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

3. 3. A driver according to any one of claims 1 to 2, wherein the converter is one of a buck converter, a boost converter, a buck-boost converter, a flyback converter or a resonant converter.

4. a third node adapted to receive the regulated voltage and adapted to be couplable to the second load; a fourth node adapted to be couplable to the second load such that the second load is couplable between the third node and the fourth node; a second capacitor coupled between the fourth node and the reference; and 4. A driver as claimed in any one of claims 1 to 3, further comprising a second load stage comprising a second switched mode power supply having a second input coupled to the fourth node and having a second output coupled to a second output node, the second switched mode power supply adapted to regulate current through the second load.

5. 5. A driver as claimed in any preceding claim, wherein the first output node is coupled to a further load.

6. 6. The driver of claim 5, wherein the first output node is further coupled to a bleeder circuit.

7. 5. A driver as claimed in any preceding claim, wherein the first output node is coupled to the first node.

8. 8. The driver of claim 7, wherein the second switched mode power supply is a boost converter or a flyback converter.

9. 9. A driver according to any one of claims 1 to 8, further comprising a controller for controlling the first switched-mode power supply, the controller being configured to control the first switched-mode power supply to regulate a current through the first load.

10. 10. The driver of claim 9, wherein the controller is part of the further load.

11. A lighting system comprising a driver according to any one of claims 1 to 10 and the first load.

12. 12. The lighting system of claim 11, wherein the first load is a solid-state lighting load.

13. 13. A lighting system according to any one of claims 11 to 12, comprising a driver according to claim 5 and the second load.

14. 14. The lighting system of claim 13, wherein the second load is a non-lighting load.

15. 15. A lighting system according to claim 13 or 14, wherein the required operating voltage of the first load is different from the required operating voltage of the second load.

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