System and method for detecting dc bus voltage while minimizing power loss in standby mode

Abstract

An LED power supply comprising: a power factor correction circuit configured to receive an input signal and provide a DC bus voltage across a DC bus; a converter configured to receive the DC bus voltage and output a DC output voltage for powering at least one LED, wherein the converter comprises a high side transistor, wherein the high side transistor is turned off when the LED power supply is in a standby state; a voltage sensor configured to output a voltage sensor output; and a controller configured to receive the voltage sensor output and output a control signal in dependence on the voltage sensor output, wherein the voltage sensor is positioned in series with an output of the high side transistor such that when the high side transistor is turned on, the voltage sensor output is proportional to the DC bus voltage, and when the high side transistor is turned off, the voltage sensor is disconnected from the DC bus.

Description

Technical Field

[0001] The following relates to systems and methods for determining the voltage of a DC bus in an LED power supply, and more specifically to systems and methods for determining the voltage of a DC bus in an LED power supply having a voltage sensor that does not consume power when the LED power supply is in standby mode. Background Technology

[0002] Figure 1 A block diagram of a typical LED power supply 100 is depicted, which includes an EMI filter 102, a power factor correction (PFC) circuit 104, a PFC controller 106, a converter 108, an output stage 110, a controller 112, a second converter 114, and a control interface 116.

[0003] When the LED power supply 100 is operating in standby mode, the converter 108 is turned off so that there is no output to the LED. The PFC circuit 104 is also turned off during standby to reduce power loss. However, the converter 114 is typically turned on to keep the control interface operational (e.g., to receive a turn-on command to bring the LED power supply 100 out of standby) and / or to power external control devices. Similarly, the controller 112 must remain operational; otherwise, the converter 108 may not restart.

[0004] Even when the LED power supply 100 is operating in standby mode, and therefore the PFC circuit 104 and converter 108 are off, the DC bus 118 connecting the PFC circuit 104 to the converter 108 is typically at the peak of the input line voltage. For example, when the input voltage is 277V, the DC bus 118 can be 392V DC. Voltage sensors 120 and 122 detect this peak voltage at the DC bus 118 and transmit proportional voltages to the PFC controller 106 and controller 112, respectively.

[0005] Because voltage sensors 120 and 122, which include resistors R1, R2 and R4, and R5 and R6 respectively, are drawing current to detect the DC bus 118 voltage, voltage sensors 120 and 122 will consume power during standby. For example, given an input voltage of 277V, voltage sensor 122 may draw 150μA, resulting in a power dissipation of 59mW. Considering a standby requirement of, for example, less than 250mW, the power consumed by voltage sensor 120 alone is quite significant. If the input voltage is 480V, the power loss in the resistors increases to 102mW. If additional resistors are used in voltage sensor 120, the power loss of voltage sensor 122 may increase. Additionally, if the power consumed by voltage sensor 122 is included, most of the power during standby is consumed solely by voltage sensors 120 and 122.

[0006] like Figure 2 As shown, when the LED power supply 100 is in standby mode, the high-voltage FET 123 can be positioned to make the voltage sensors 120 and 122 (in) Figure 2 In the process, they have been combined to form a single string (which is then disconnected). This arrangement prevents voltage sensors 120 and 122 from consuming power during standby, but it has several drawbacks. First, Figure 2 The arrangement requires an additional high-voltage FET 123, which is a relatively expensive component. Secondly, Figure 2 The arrangement requires additional signals to drive the high-voltage FET 123, which in turn requires additional outputs from the controller (e.g., controller 112), thus adding another layer of complexity.

[0007] Therefore, there is a need in this field to detect the voltage of the DC bus in an LED power supply while minimizing the power loss of the voltage sensor when the LED power supply is in standby mode. Summary of the Invention

[0008] The various examples disclosed herein describe a system and method for detecting the voltage of a DC bus while minimizing power loss of the voltage sensor when the LED power supply is in standby mode. In one example, the voltage sensor may be positioned in series with the output of the high-side transistor of a DC-DC converter, such that the voltage sensor outputs a voltage proportional to the DC bus voltage while the high-side transistor is on, and disconnects from the DC bus when the high-side transistor is off.

[0009] According to one aspect, an LED power supply includes a power factor correction circuit configured to receive an input signal and provide a DC bus voltage across a DC bus; a converter configured to receive the DC bus voltage and output a DC output voltage for powering at least one LED, wherein the converter includes a high-side transistor that is turned off when the LED power supply is in standby mode; a voltage sensor configured to output a voltage sensor output; and a controller configured to receive the voltage sensor output and output a control signal based on the voltage sensor output, wherein the voltage sensor is positioned in series with the output of the high-side transistor such that when the high-side transistor is on, the voltage sensor output is proportional to the DC bus voltage, and when the high-side transistor is off, the voltage sensor is disconnected from the DC bus.

[0010] In one example, the LED power supply also includes a peak detector configured to make the voltage sensor output proportional to the peak value of the DC bus voltage.

[0011] In one example, the peak detector is set at the output of the high-side transistor.

[0012] In one example, a peak detector is set at the output of the voltage sensor.

[0013] In one example, the controller is configured to average the voltage sensor output.

[0014] In one example, the controller is configured to sample the voltage sensor output only when the high-side transistor is on.

[0015] In one example, the controller is configured to output a control signal to the power factor correction circuit based on the voltage sensor output.

[0016] In one example, the controller is configured to output a control signal to the converter based on the voltage sensor output.

[0017] In one example, the converter is one of the following: a half-bridge converter, a full-bridge converter, a buck converter, a dual-switch flyback converter, or a dual-switch forward converter.

[0018] In one example, when the high-side transistor is turned on, the voltage sensor outputs a current proportional to the DC bus voltage, wherein the controller is configured to determine the DC bus voltage based on the current output by the voltage sensor.

[0019] In one example, when the high-side transistor is turned on, the voltage sensor outputs a voltage proportional to the DC bus voltage, wherein the controller 112 is configured to determine the DC bus voltage based on the voltage sensor output.

[0020] In one example, the voltage sensor is a voltage divider.

[0021] In one example, the LED power supply also includes a second voltage sensor configured to output a second voltage sensor output; and a second controller configured to receive the second voltage sensor output and output a second control signal based on the second voltage sensor output, wherein the second voltage sensor is positioned in series with the output of the high-side transistor such that when the high-side transistor is turned on, the second voltage sensor output is proportional to the DC bus voltage, and when the high-side transistor is turned off, the second voltage sensor is disconnected from the DC bus.

[0022] According to another aspect, a method for sensing a DC bus in an LED power supply includes the following steps: providing a power factor correction circuit, a converter, and a voltage sensor, the power factor correction circuit being configured to receive an input signal and provide a DC bus voltage across the DC bus, the converter being configured to receive the DC bus voltage and output a DC output voltage for powering at least one LED, wherein the converter includes a high-side transistor that is turned off when the LED power supply is in standby mode, and the voltage sensor being configured to output a voltage sensor output, wherein the voltage sensor is positioned in series with the output of the high-side transistor such that when the high-side transistor is on, the voltage sensor output is proportional to the DC bus voltage, and when the transistor is off, the voltage sensor is disconnected from the DC bus; detecting the voltage sensor output via a controller; and outputting a control signal via the controller based on the voltage sensor output.

[0023] In one example, the method further includes the step of providing a peak detector configured such that the voltage sensor output is proportional to the peak value of the DC bus voltage.

[0024] In one example, the controller is configured to detect the voltage sensor output only when the high-side transistor is on.

[0025] In one example, a control signal is output to a power factor correction circuit.

[0026] In one example, a control signal is output to the converter.

[0027] In one example, when the high-side transistor is turned on, the voltage sensor outputs a current proportional to the DC bus voltage, wherein the controller is configured to determine the DC bus voltage based on the current output by the voltage sensor.

[0028] In one example, when the high-side transistor is turned on, the voltage sensor outputs a voltage proportional to the DC bus voltage, wherein the controller 112 is configured to determine the DC bus voltage based on the voltage sensor output.

[0029] In one example, the voltage sensor is a voltage divider.

[0030] These and other aspects of the various embodiments will become apparent from one or more embodiments described below and will be illustrated with reference to the embodiments described below. Attached Figure Description

[0031] In accompanying drawings, the same reference numerals typically refer to the same parts in different views. Furthermore, the drawings are not necessarily drawn to scale; rather, the focus is usually on illustrating the principles governing the various aspects.

[0032] Figure 1 The LED power supply is described.

[0033] Figure 2 A partial schematic diagram of a voltage sensor according to an example and a high-voltage FET positioned to prevent the voltage sensor from consuming power is depicted.

[0034] Figure 3 An LED power supply employing a voltage sensor at the output of the high-side transistor of the converter is depicted according to an example.

[0035] Figure 4 An LED power supply with a voltage sensor and a peak detector at the output of the high-side transistor of the converter is depicted according to an example.

[0036] Figure 5 A partial schematic diagram depicts multiple voltage sensors and a peak detector connected at the output of the high-side transistor of the converter, according to an example. Detailed Implementation

[0037] The various examples described herein relate to an LED power supply with a voltage sensor that is advantageously connected in series with the high-side transistor of the converter to detect the DC bus voltage but does not consume power when the LED power supply is in standby mode.

[0038] Now, turn to Figure 3 The diagram illustrates an LED power supply 200, which includes an EMI filter 102, a PFC circuit 104, a PFC controller 106, a converter 108, an output stage 110, a controller 112, a second converter 114, and a control interface 116. The LED power supply typically receives an input as AC mains voltage. The LED power supply 200 can be configured to enter a standby mode, in which at least the PFC controller 106 and the converter 108 are turned off, and the LED power supply 200 stops outputting LED output.

[0039] Generally, EMI filter 102 filters noise from AC mains voltage. PFC circuit 104 is primarily used to convert the input voltage into a DC signal with low harmonic distortion. PFC circuit 104 can be any suitable circuit for performing power factor control, including, for example, buck or boost PFC circuits, although other PFC circuits are known and may be used herein. PFC circuit outputs the DC voltage across DC bus 118 to converter 108, where the DC voltage is down-converted to a lower DC voltage that can be used by output stage 110 to generate an output for driving LEDs. PFC controller 106 is typically used, for example, to drive the transistor-operated PFC circuit 104 located within PFC circuit 104 via an output signal. PFC controller 106 can also be powered, for example, by converter 114, which also supplies power to control interface 116 (which can receive control inputs) for LED power supply and to auxiliary power output (AUX Power) for powering external devices such as external controllers. The controller 112 can be configured to control the operation of the converter 108 (e.g., the operation of the high-side transistor 124 and the low-side transistor 126, as described below) by outputting control signals. The controller 112 can also be configured to receive input commands from the control interface 116 and sense the output stage 110 for generating LED output signals.

[0040] Both PFC controller 106 and controller 112 can be implemented as, for example, a microcontroller. However, in alternative examples, both PFC controller 106 and controller 112 can be implemented with any necessary hardware or firmware. In one example, both PFC controller 106 and controller 112 can be implemented by a single microcontroller or multiple microcontrollers. In fact, the individual functionality of PFC controller 106 or controller 112 can be implemented by one or more controllers working in concert.

[0041] As described below, voltage sensors 120 and 122 are positioned to sense the voltage of DC bus 118 and provide voltage sensor output signals proportional to the voltage of DC bus 118 to PFC controller 106 and controller 112. Therefore, voltage sensors 120 and 122 can be composed of resistors such as resistors R1 and R2 and resistors R4, R5, and R6, although it should be understood that other configurations of resistors and other types of voltage sensors can be used as alternative examples. The output of voltage sensor 120 is located at the output of R2, while the output of voltage sensor 122, acting as a voltage divider, will be the connection of resistors R5 and R6. The output of voltage sensor 120 is a current proportional to the DC bus voltage. PFC controller 106 detects the current output from voltage sensor 120 and can determine from it a value representing the DC bus voltage. The output of voltage sensor 122 is a voltage proportional to the DC bus voltage, which is detected at controller 112. Generally, the outputs of voltage sensors 120 and 122 form feedback signals provided to PFC controller 106 and controller 112.

[0042] PFC controller 106 can generate control signals for PFC circuit 104 based on feedback signals received from voltage sensor 120 to control the operation of PFC circuit 104 (e.g., the control signals can drive transistors disposed within PFC circuit 104). Similarly, controller 112 can control the operation of converter 108 based on voltage sensor output signals received from voltage sensor 122. For example, as mentioned above, controller 112 can be configured to generate control signals for controlling high-side transistor 124 or low-side transistor 126 based on voltage sensor output signals received from sensor 122. The values ​​of the resistors can be set such that the inputs to PFC controller 106 and controller 112 do not exceed the maximum permissible input of either controller.

[0043] Converter 108 can be any DC-DC converter, such as a half-bridge converter, full-bridge converter, buck converter, dual-switch flyback converter, or dual-switch forward converter, utilizing a high-side transistor. In such a converter, the high-side transistor is connected to the DC bus voltage and is typically used as part of the DC-DC conversion operation of converter 108 (that is, the high-side transistor is at least partially used to convert the DC input voltage to a lower DC output voltage). When the converter operates, the high-side transistor is turned on for at least a period of time such that its output is substantially similar to the voltage of the DC bus 118 to which it is connected (in this document, "substantially similar" takes into account the minimum losses inherent in the operation of the high-side transistor). Figure 3 and Figure 4In the example, converter 108 is a half-bridge converter, including a high-side transistor 124 and a low-side transistor 126. During operation of the half-bridge converter, the high-side transistor 124 typically operates to output a square wave with a 50% duty cycle. When the high-side transistor 124 is turned on, the voltage of the square wave is substantially similar to the voltage of the DC bus 118.

[0044] Therefore, voltage sensors 120 and 122 can be connected in series with the output of the high-side transistor 124 of converter 108. For example, as Figure 3 As shown, voltage sensors 120 and 122 are connected in series with the output of high-side transistor 124, such that when high-side transistor 124 is turned on, the outputs of voltage sensors 120 and 122 are proportional to the voltage of DC bus 118. Therefore, PFC controller 106 and controller 112 receive voltages proportional to the voltage of DC bus 118 from voltage sensors 120 and 122, respectively, while the high-side transistor is turned on. However, when LED power supply 200 is in standby mode, high-side transistor 124 is turned off, thus disconnecting voltage sensors 120 and 122 from DC bus 118 and stopping power consumption. Positioning voltage sensors 120 and 122 at the output of high-side transistor 124 advantageously utilizes the existing functionality and topology of converter 108 to disconnect voltage sensors 120 and 122 from DC bus 118 during standby.

[0045] While converter 108 is operating, high-side transistor 124 is turned on periodically. For example, as mentioned above, converter 108 can output a square wave with a 50% duty cycle. In this example, high-side transistor 124 will be on for 50% of the time during the operation of converter 108. Therefore, PFC controller 106 and controller 112 can be configured to average the outputs of voltage sensors 120, 122 to account for the off-time of high-side transistor 124. Because for a 50% duty cycle, the average value of the output of high-side transistor 124 will be proportionally half the value of the DC bus 118 voltage, voltage sensors 120, 122 can be configured to increase their outputs accordingly. For example, the resistance of resistor R6 can be doubled to double the amplitude of the output of voltage sensor 122.

[0046] Alternatively, controller 112 and PFC controller 106 can be configured to sample voltage sensors 120 and 122 only when high-side transistor 124 is turned on. For example, controller 112 and PFC controller 106 can be configured to sample voltage sensors 120 and 122 only when the output of voltage sensors 120 and 122 is non-zero.

[0047] Because most existing microcontrollers are configured to receive continuous inputs and do not necessarily include the ability to average the inputs or operate only when the inputs are non-zero, a peak detector 128 can be employed to maintain the output values ​​of voltage sensors 120, 122 proportional to the peak value of the DC bus 118 voltage while the converter 108 is operating. Figure 4 This example is shown. Figure 4 The LED power supply 300 is depicted. Components are combined except for the peak detector 128. Figure 3 Therefore, no further details will be provided.

[0048] As shown, peak detector 128 can be positioned in series with the output of high-side transistor 124 to maintain the inputs of voltage sensors 120, 122 at a value substantially equal to the peak value of the DC bus voltage (considering the losses of high-side transistor 124 and diode D1). Therefore, when high-side transistor 124 is on and converter 108 is operating, the outputs of voltage sensors 120, 122 will be proportional to the peak value of DC bus voltage 118. Alternatively, peak detector 128 can be located at one or both outputs of voltage sensors 120, 122 to maintain the outputs of voltage sensors 120, 122 (e.g., between the outputs of voltage sensors 120, 122 and the inputs of PFC controller 106 and controller 112, respectively) at a value proportional to the peak value of DC bus voltage 118. For example, peak detector 128 can be placed in parallel with resistor R6 of voltage sensor 122. As shown, peak detector 128 may include diode D1 and capacitor C1. However, other peak detectors are known in the art and can be substituted as needed.

[0049] As mentioned above, it should also be understood that LED power supplies 200 and 300 are provided only as examples, and the systems and methods described herein can be used in conjunction with any LED power supply that utilizes a converter with a high-side transistor to which a voltage sensor can be connected, such that the voltage sensor is disconnected from the DC bus when the LED power supply is in standby mode.

[0050] It should also be understood that, although Figure 2 and Figure 3Two voltage sensors 120 and 122 are shown, but in alternative examples, only one of voltage sensors, 120 or 122, can be implemented. For example, in one alternative example, only voltage sensor 120 is used. Furthermore, depending on the specific LED power supply requirements in which the voltage sensor is used, additional voltage sensors besides voltage sensor 120 or 122 can be implemented. For example, in an alternative embodiment, additional controllers requiring additional voltage inputs can be implemented, each controller receiving a separate voltage detection input from the corresponding additional voltage sensor. Additionally, each voltage sensor does not necessarily provide an output to only one controller. Indeed, as... Figure 2 As shown, voltage sensors 120 and 122 can be combined into a single string, which provides output to multiple controllers (e.g., PFC controller 106 and controller 112).

[0051] In addition, as Figure 2 and Figure 3 As shown, it is not necessary to configure each voltage sensor. For example, Figure 5 Alternative examples of voltage sensors 120 and 122 are shown. As illustrated, voltage sensors 120 and 122 each include six resistors instead of two. The number and value of the resistors used for the voltage sensors will depend on the magnitude of the voltage at the input of the voltage sensor (e.g., the value of Vbus) and the input parameters of the controller or other components in which the voltage sensor supplies the sensed voltage.

[0052] For example, resistors R7, R8, R9, and R10 can each have a value of 1 MOhm, while resistors R1 and R2 can have values ​​of 680 KΩ and 220 KΩ, respectively, to regulate the current 106 sensed at the PFC controller. The current sensed at the PFC controller 106 through the voltage sensor 120 is converted into a voltage to measure the VBUS voltage. Similarly, resistors R11, R12, R13, and R4 can each have a value of 1 MOhm, while resistors R5 and R6 can have values ​​of 10KΩ and 8KΩ, respectively, to adjust the voltage received at the controller 112 according to the VBUS voltage value and the input requirements of the controller 112.

[0053] As disclosed herein, the idea described in conjunction with the description of LED power supplies 200 and 300 advantageously positions the voltage sensor for detecting DC bus voltage, but without consuming power when the LED power supply is in standby mode. Additionally, no additional expensive components such as high-voltage FETs are required to achieve this low-power voltage sensing; instead, the voltage sensor is advantageously disconnected from the DC bus using the existing topology of the converter.

[0054] The functions or portions thereof described herein and their various modifications (hereinafter referred to as "functions") may be implemented, at least in part, by a computer program product (e.g., a computer program tangibly embodied in an information carrier such as one or more non-transitory machine-readable media or storage devices) for execution or control of their operation by one or more data processing devices (e.g., a programmable processor, a computer, multiple computers and / or programmable logic components).

[0055] Computer programs can be written in any programming language, including compiled or interpreted languages, and can be deployed in any form, including as standalone programs or as modules, components, subroutines, or other units suitable for a computing environment. Computer programs can be deployed to execute on one computer or multiple computers at one site, or distributed across multiple sites and interconnected via a network.

[0056] The actions associated with all or part of the functions implemented can be performed by one or more programmable processors, which execute one or more computer programs to perform the functions of the calibration process. All or part of the functions can be implemented as special-purpose logic circuits, such as FPGAs and / or ASICs (Application-Specific Integrated Circuits).

[0057] Processors suitable for executing computer programs include, for example, general-purpose microprocessors and special-purpose microprocessors, as well as one or more processors of any type of digital computer. Typically, the processor receives instructions and data from read-only memory or random access memory, or both. The components of a computer include a processor for executing instructions and one or more memory devices for storing instructions and data.

[0058] While several embodiments of the invention have been described and illustrated herein, those skilled in the art will readily conceive of various other means and / or structures for performing functions and / or obtaining results and / or one or more of the advantages described herein, and each such variation and / or modification is considered to be within the scope of the embodiments of the invention described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are intended to be exemplary, and actual parameters, dimensions, materials, and / or configurations will depend on one or more specific applications in which the teachings of the invention are used. Those skilled in the art will recognize or be able to confirm many equivalents of the particular embodiments of the invention described herein using only conventional experimentation. Therefore, it should be understood that the foregoing embodiments are presented as examples only, and that the embodiments of the invention may be implemented in ways different from the specific descriptions and claims within the scope of the appended claims and their equivalents. The embodiments of the invention disclosed herein relate to each individual feature, system, article of manufacture, material, and / or method described herein. Furthermore, if any combination of two or more such features, systems, articles, materials and / or methods is not contradictory, then such features, systems, articles, materials and / or methods are included within the scope of the invention.

Claims

1. An LED power supply (100), comprising: The power factor correction circuit (104) is configured to receive the input signal and provide the DC bus voltage across the DC bus (118); A converter (108) is configured to receive the DC bus voltage and output a DC output voltage for powering at least one LED, wherein the converter (108) includes a high-side transistor (124) which is turned off when the LED power supply (100) is in standby mode. Voltage sensors (120, 122) are configured to output voltage sensor outputs; as well as The controller (106, 112) is configured to receive the voltage sensor output and output a control signal to the power factor correction circuit (104) based on the voltage sensor output, wherein the voltage sensor is positioned in series with the output of the high-side transistor such that when the high-side transistor is turned on, the voltage sensor output is proportional to the DC bus voltage, and when the high-side transistor is turned off, the voltage sensor is disconnected from the DC bus. A peak detector (128) is configured such that the output of the voltage sensors (120, 122) is proportional to the peak value of the DC bus voltage; and wherein the peak detector (128) is disposed between the output of the high-side transistor (124) and the voltage sensor.

2. The LED power supply (100) according to claim 1, wherein the peak detector (128) comprises a diode and a capacitor.

3. The LED power supply (100) according to claim 1, wherein the controller (106, 112) is configured to average the output of the voltage sensor (120, 122).

4. The LED power supply (100) according to claim 1, wherein the controller (106, 112) is configured to sample the output of the voltage sensor (120, 122) only when the high-side transistor (124) is turned on.

5. The LED power supply (100) according to claim 1, wherein the controller (112) is configured to output the control signal to the converter (108) according to the output of the voltage sensor (122).

6. The LED power supply (100) according to claim 1, wherein the converter (108) is one of the following: a half-bridge converter, a full-bridge converter, a buck converter, a dual-switch flyback converter, or a dual-switch forward converter.

7. The LED power supply (100) according to claim 1, wherein when the high-side transistor (124) is turned on, the voltage sensor output of the voltage sensor (120) is a current proportional to the DC bus voltage, wherein the controller (106) is configured to determine the DC bus voltage based on the current output by the voltage sensor.

8. The LED power supply (100) according to claim 1, wherein when the high-side transistor (124) is turned on, the voltage sensor output (122) is a voltage proportional to the DC bus voltage, wherein the controller 112 is configured to determine the DC bus voltage based on the voltage sensor output.

9. The LED power supply (100) according to claim 8, wherein the voltage sensor is a voltage divider.

10. The LED power supply (100) according to claim 1, further comprising: The second voltage sensor (120, 122) is configured to output the second voltage sensor output; as well as The second controller (106, 112) is configured to receive the output of the second voltage sensor and output a second control signal based on the output of the second voltage sensor, wherein the second voltage sensor is positioned in series with the output of the high-side transistor such that when the high-side transistor (124) is turned on, the output of the second voltage sensor is proportional to the DC bus voltage, and when the high-side transistor is turned off, the second voltage sensor is disconnected from the DC bus (118).

11. A method for sensing a DC bus (118) in an LED power supply (100), comprising the steps of: A power factor correction circuit (104), a converter (108), and voltage sensors (120, 122) are provided. The power factor correction circuit (104) is configured to receive an input signal and provide a DC bus voltage across a DC bus (118). The converter (108) is configured to receive the DC bus voltage and output a DC output voltage for powering at least one LED. The converter includes a high-side transistor (124) which is turned off when the LED power supply (100) is in standby mode. The voltage sensors (120, 122) are configured to output a voltage sensor output, wherein the voltage sensor is positioned in series with the output of the high-side transistor such that when the high-side transistor is on, the voltage sensor output is proportional to the DC bus voltage, and when the transistor is off, the voltage sensor is disconnected from the DC bus. The voltage sensor output is detected by the controller (106, 112); as well as The controller outputs a control signal based on the output of the voltage sensor. A peak detector (128) is provided, which is disposed between the output of the high-side transistor and the voltage sensors (120, 122) such that the output of the voltage sensors (120, 122) is proportional to the peak value of the DC bus voltage; and wherein the controller (106, 112) is configured to detect the output of the voltage sensors (120, 122) only when the high-side transistor (124) is turned on; The control signal is output to the power factor correction circuit (104).

12. The method of claim 11, wherein the control signal is output to the converter (108).

13. The method of claim 11, wherein when the high-side transistor (124) is turned on, the voltage sensor output of the voltage sensor (120) is a current proportional to the DC bus voltage, wherein the controller (106) is configured to determine the DC bus voltage based on the current output by the voltage sensor.

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