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

Abstract

The 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, the converter having a high-side transistor, the high-side transistor being off when the LED power supply is in standby; a voltage sensor configured to output a voltage sensor output, the voltage sensor being disposed in series with an 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; and a controller configured to receive the voltage sensor output and output a control signal according to the voltage sensor output.

Description

Technical Field

[0001] The following relates to a system and method for determining the voltage of a DC bus in an LED power supply, and more particularly to determining the voltage of the DC bus in an LED power supply with a voltage sensor that consumes no power while the LED power supply is in standby.

Background Art

[0002] FIG. 1 shows a block diagram of a typical LED power supply 100 having 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 off so that there is no output to the LEDs. During standby, the PFC circuit 104 is also off to reduce power consumption. However, the converter 114 is generally on to maintain the function of the control interface (e.g., to receive an on command to bring the LED power supply 100 out of standby) and / or to power an external control device. Similarly, the controller 112 must remain operational, or else the converter 108 may not restart.

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

[0005] The voltage sensors 120 and 122, each having resistors R1 and R2 and R4, R5, and R6, draw current to detect the voltage of the DC bus 118. Therefore, the voltage sensors 120 and 122 consume power during standby. For example, considering an input voltage of 277V, the voltage sensor 122 draws 150 μA and can result in a power waste of 59 mW. Considering a standby requirement of less than 250 mW, for example, the power consumed by the voltage sensor 120 alone is significant. When the input voltage is 480V, the power loss in the resistor increases to 102 mW. If an additional resistor is used in the voltage sensor 120, the power consumption by the voltage sensor 122 can increase. Furthermore, when the power wasted by the voltage sensor 122 is included, most of the power during standby is consumed only by the voltage sensors 120 and 122.

[0006] As shown in FIG. 2, a high-voltage FET 123 may be arranged to disconnect the voltage sensors 120 and 122 (coupled to a single string in FIG. 2) when the LED power supply 100 is in the standby mode. This configuration prevents the voltage sensors 120 and 122 from consuming power during standby, but has many disadvantages. First, the configuration of FIG. 2 requires an additional high-voltage FET 123, which is a relatively expensive component. Second, the configuration of FIG. 2 requires an additional signal to drive the high-voltage FET 123, which requires an additional output from a controller (e.g., controller 112) and adds another level of complexity.

SUMMARY OF THE INVENTION

PROBLEM TO BE SOLVED BY THE INVENTION

[0007] Therefore, there is a need in the art to detect the voltage of the DC bus in the LED power supply while minimizing the power consumption of the voltage sensor while the LED power supply is in standby.

MEANS FOR SOLVING THE PROBLEM

[0008] The various examples disclosed herein describe systems and methods for detecting the voltage of a DC bus while minimizing the power consumption of a voltage sensor while the LED power supply is in standby. In one example, the voltage sensor outputs a voltage proportional to the DC bus voltage while the high-side transistor is on, and is disconnected from the DC bus when the high-side transistor is off, and can be arranged in series with the output of the high-side transistor of the DC-DC converter.

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

[0010] In an example, the LED power supply further includes a peak detector arranged such that the voltage sensor output is proportional to the peak of the DC bus voltage.

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

[0012] In an example, the peak detector is arranged at the output of the voltage sensor.

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

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

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

[0016] In the example, the controller is configured to output the control signal to the converter according to the voltage sensor output.

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

[0018] In the example, the voltage sensor output of the voltage sensor is a current proportional to the DC bus voltage when the high-side transistor is on, and the controller is configured to determine the DC bus voltage according to the current of the voltage sensor output.

[0019] In the example, the voltage sensor output is a voltage proportional to the DC bus voltage when the high-side transistor is on, and the controller is configured to determine the DC bus voltage according to the voltage sensor output.

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

[0021] In the example, the LED power supply includes a second voltage sensor configured to output a second voltage sensor output. When the high-side transistor is on, the second voltage sensor output is proportional to the DC bus voltage. When the high-side transistor is off, the second voltage sensor is arranged in series with the output of the high-side transistor such that the second voltage sensor is disconnected from the DC bus. The LED power supply further includes a second controller configured to receive the second voltage sensor output and output a second control signal according to the second voltage sensor output.

[0022] According to another aspect, a method for detecting a DC bus in an LED power supply includes receiving an input signal, a power factor correction circuit configured to supply a DC bus voltage across the DC bus, a converter configured to receive the DC bus voltage and output a DC output voltage for powering at least one LED, the converter having a high-side transistor and the high-side transistor being off when the LED power supply is in standby, providing a voltage sensor configured to output a voltage sensor output, the voltage sensor being arranged 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, detecting, by a controller, the voltage sensor output, and outputting, by the controller, a control signal according to the voltage sensor output.

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

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

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

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

[0027] In the example, the voltage sensor output of the voltage sensor is a current proportional to the DC bus voltage when the high-side transistor is on, and the controller is configured to determine the DC bus voltage according to the current of the voltage sensor output.

[0028] In the example, the voltage sensor output is a voltage proportional to the DC bus voltage when the high-side transistor is on, and the controller is configured to determine the DC bus voltage according to the voltage sensor output.

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

[0030] With reference to the following embodiments, these and other aspects of various embodiments are described and clarified.

Brief Description of the Drawings

[0031] In the figures, like reference numerals generally refer to the same parts throughout the various figures. Also, the drawings are not necessarily to scale, but rather are generally weighted towards explaining the principles of the various aspects.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0032] The various examples described herein detects the DC bus voltage, are advantageously directed to an LED power supply having a voltage sensor arranged in series with the high-side transistor of the converter so as not to consume power when the LED power supply is in standby. is When the LED power supply is in standby.

[0033] Turning now to FIG. 3, there is shown an LED power supply 200 having 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 generally receives an input as an 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 switched off and the LED power supply 200 stops outputting an LED output.

[0034] Generally, the EMI filter 102 filters noise from the AC main power supply voltage. The PFC circuit 104 mainly functions to convert the input voltage into a DC signal with less harmonic distortion. The PFC circuit 104 may be any suitable circuit for implementing power factor control, including, for example, a buck or boost PFC circuit. However, other PFC circuits are known and may be used here. The PFC circuit outputs a DC voltage across the DC bus 118 to the converter 108, and the DC voltage is down-converted in the converter 108 to a lower DC voltage that can be used by the output stage 110 to generate an output for driving the LEDs. The PFC controller 106 generally functions to operate the PFC circuit 104 by outputting a signal for driving a transistor, for example, disposed within the PFC circuit 104. The PFC controller 106 may also be powered by a converter 114 that supplies power to, for example, a control interface 116 (the control interface 116 can receive control inputs) for the LED power supply and an auxiliary power output AUX Power for powering external devices such as an external controller. The controller 112 may 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 a control signal. The controller 112 may also be configured to receive an input command from the control interface 116 and sense the output stage 110 to generate an LED output signal.

[0035] The PFC controller 106 and the controller 112 may each be implemented, for example, as a microcontroller. However, in an alternative example, the PFC controller 106 and the controller 112 may each be implemented in combination with any necessary hardware or firmware. In an example, the PFC controller 106 and the controller 112 may each be implemented by a single or multiple microcontrollers. In practice, the individual functions of the PFC controller 106 or the controller 112 may be implemented by one or more controllers that function cooperatively.

[0036] Voltage sensors 120 and 122, as described below, sense the voltage of the DC bus 118 and are arranged to supply a voltage sensor output signal proportional to the voltage of the DC bus 118 to the PFC controller 106 and the controller 112. Accordingly, the voltage sensors 120 and 122 may be composed of resistors such as resistors R1 and R2, and resistors R4, R5, and R6. However, in an alternative example, it should be understood that other configurations of resistors and other types of voltage sensors may be used. The output of the voltage sensor 120 is at the output of R2, while the output of the voltage sensor 122, which is a voltage divider, is at the connection of resistors R5 and R6. The output of the voltage sensor 120 is a current proportional to the DC bus voltage. The PFC controller 106 can detect the current output from the voltage sensor 120 and determine a value representing the DC bus voltage from the said current. The output of the voltage sensor 122 is a voltage proportional to the DC bus voltage, and the said voltage is detected by the controller 112. Generally, the outputs of the voltage sensors 120 and 122 form a feedback signal supplied to the PFC controller 106 and the controller 112.

[0037] The PFC controller 106 may generate a control signal to the PFC circuit 104 according to the feedback signal received from the voltage sensor 120 to control the operation of the PFC circuit 104 (for example, the control signal may drive a transistor arranged within the PFC circuit 104). Similarly, the controller 112 may control the operation of the converter 108 according to the voltage sensor output signal received from the voltage sensor 122. For example, as described above, the controller 112 may be configured to generate a control signal for controlling the high-side transistor 124 or the low-side transistor 126 according to the voltage sensor output signal received from the sensor 122. The values of the resistors may be set so that the inputs to the PFC controller 106 and the controller 112 do not exceed the maximum allowable input of either controller.

[0038] Converter 108 can be any DC-DC converter that utilizes a high-side transistor, such as a half-bridge converter, a full-bridge converter, a buck converter, a two-switch flyback converter, or a two-switch forward converter. In such a converter, the high-side transistor is associated with the DC bus voltage and generally functions as part of the DC-DC conversion operation of converter 108 (i.e., the high-side transistor is used, at least in part, to convert the DC input voltage to a lower DC output voltage). When the converter is operating, the high-side transistor is on such that its output is substantially the same as the voltage of the DC bus 118 to which the high-side transistor is connected for at least some period (where "substantially the same" takes into account the minimum losses inherent in the operation of the high-side transistor). In the examples of FIGS. 3 and 4, converter 108 is a half-bridge converter that includes a high-side transistor 124 and a low-side transistor 126. During operation of the half-bridge converter, the high-side transistor 124 generally operates to output a rectangular wave having a duty cycle of 50%. The voltage of the rectangular wave when the high-side transistor 124 is on is substantially the same as the voltage of the DC bus 118.

[0039] Accordingly, the voltage sensors 120, 122 may be connected in series with the output of the high-side transistor 124 of the converter 108. For example, as shown in FIG. 3, the voltage sensors 120, 122 are in series with the output of the high-side transistor 124 such that the outputs of the voltage sensors 120, 122 are proportional to the voltage of the DC bus 118 when the high-side transistor 124 is on. Accordingly, the PFC controller 106 and the controller 112 each receive a voltage proportional to the voltage of the DC bus 118 from the voltage sensors 120, 122 while the high-side transistor is on. However, when the LED power supply 200 is in standby, the high-side transistor 124 is off, and accordingly, the voltage sensors 120, 122 are disconnected from the DC bus 118 and, in response, stop consuming power. Placing the voltage sensors 120, 122 at the output of the high-side transistor 124 advantageously uses the existing functions and topology of the converter 108 to disconnect the voltage sensors 120, 122 from the DC bus 118 during standby.

[0040] While the converter 108 is operating, the high-side transistor 124 is periodically on. For example, as described above, the converter 108 may output a rectangular wave having a 50% duty cycle. In that example, the high-side transistor 124 is on for 50% of the period during the operation of the converter 108. Accordingly, the PFC controller 106 and the controller 112 may be configured to average the outputs of the voltage sensors 120, 122 to account for the period during which the high-side transistor 124 is off. Since the average of the output of the high-side transistor 124 is proportionally half of the value of the voltage of the DC bus 118 in the case of a 50% duty cycle, the voltage sensors 120, 122 may be configured to increase their outputs accordingly. For example, the resistance value of the resistor R6 may be doubled to double the magnitude of the output of the voltage sensor 122.

[0041] In other examples, the controller 112 and the PFC controller 106 may be configured to sample the outputs of the voltage sensors 120, 122 only when the high-side transistor 124 is on. For example, the controller 112 and the PFC controller 106 may be configured to sample the outputs of the voltage sensors 120, 122 only when the outputs of the voltage sensors 120, 122 are non-zero values.

[0042] Most existing microcontrollers are configured to receive continuous inputs and do not necessarily include a function to average the inputs or a function that operates only when the input is non-zero. Therefore, while the converter 108 is operable, a peak detector 128 may be employed to maintain the outputs of the voltage sensors 120, 122 at values proportional to the peak of the voltage of the DC bus 118. Such an example is shown in FIG. 4 showing the LED power supply 300. The components other than the peak detector 128 have been described in connection with FIG. 3 and will not be described further herein.

[0043] As shown, peak detector 128 may be arranged in series with the output of high-side transistor 124 to maintain the inputs to voltage sensors 120, 122 at a value substantially equal to the peak value of the DC bus voltage (taking into account the losses of high-side transistor 124 and diode D1). Thus, the outputs of voltage sensors 120, 122 are proportional to the peak of the voltage on DC bus 118 when high-side transistor 124 is on and converter 108 is operating. In other examples, peak detector 128 may be arranged on one or both of the outputs of voltage sensors 120, 122 to maintain the outputs of voltage sensors 120, 122 (e.g., the outputs between the outputs of voltage sensors 120, 122 and the inputs to PFC controller 106 and controller 112, respectively) at a value proportional to the peak value of the voltage on DC bus 118. For example, peak detector 128 may be arranged in parallel with resistor R6 of voltage sensor 122. Peak detector 128 may have diode D1 and capacitor C1 as shown. However, other peak detectors are known in the art and may be substituted as appropriate.

[0044] As described above, LED power supplies 200, 300 are merely shown as examples, and it should also be understood that the systems and methods described herein can be used with any LED power supply that utilizes a converter having 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.

[0045] In FIGS. 2 and 3, two voltage sensors 120, 122 are shown, but it should be understood that in an alternative embodiment, only one of the voltage sensor 120 or the voltage sensor 112 may be implemented. For example, in an alternative embodiment, only the voltage sensor 120 is used. Further, additional voltage sensors other than the voltage sensor 120 or the voltage sensor 122 may be implemented depending on the requirements of a particular LED power supply where the voltage sensor is used. For example, in an alternative embodiment, an additional controller that requires an additional voltage input may be implemented, and each controller receives a separate voltage sense input from its respective additional voltage sensor. Further, it is not essential that each voltage sensor supplies only one output to one controller. In fact, as shown in FIG. 2, the voltage sensors 120, 122 may be integrated into a single string that supplies outputs to a plurality of controllers (e.g., the PFC controller 106 and the controller 112).

[0046] Further, each voltage sensor does not have to be configured exactly as shown in FIGS. 2 and 3. For example, an alternative example of the voltage sensors 120, 122 is shown in FIG. 5. As shown, the voltage sensors 120 and 122 each have six resistors instead of two. The number and value of the resistors used in the voltage sensor 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 component to which the voltage sensed by the voltage sensor is supplied.

[0047] For example, resistors R7, R8, R9, and R10 may each have a value of 1 MΩ, while resistors R1 and R2 have values of 680 kΩ and 220 kΩ, respectively, to adjust the current sensed in the PFC controller 106. The current passing through the voltage sensor 120 and sensed in the PFC controller 106 is converted to a voltage to measure the VBUS voltage. Similarly, resistors R11, R12, R13, and R4 may each have a value of 1 MΩ, while resistors R5 and R6 may have values of 10 kΩ and 8 kΩ, respectively, to adjust the value of the voltage received in the controller 112 according to the value of the Vbus voltage and the input requirements of the controller 112.

[0048] As disclosed herein, the concepts described in connection with the LED power supplies 200, 300 advantageously detects the DC bus voltage, when the LED power supply is in standby 、 arrange the voltage sensor so as not to consume power. Further, to implement such low-power voltage sensing, no additional expensive components such as high-voltage FETs are required. Rather, advantageously, the voltage sensor is disconnected from the DC bus using the existing topology of the converter.

[0049] The functions described herein, or parts thereof, and their various modifications (hereinafter, "functions") can be implemented, at least in part, via a computer program tangibly embodied in one or more non-transitory machine-readable media or storage devices, such as one or more data processing devices, such as programmable processors, computers, multiple computers, and / or programmable logic components, for execution or to control the operation of the one or more data processing devices.

[0050] A computer program can be described in any form of programming language, including a compiled language or an interpreted language, and can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit of construction suitable for use in a computing environment. The computer program can be deployed to be executed on one computer, or at one site, or distributed among multiple computers interconnected by a network and located at multiple sites.

[0051] Operations associated with performing all or part of the functions can be performed by one or more programmable processors executing one or more computer programs for performing the functions of the calibration process. All or part of the functions can be implemented as dedicated logic circuitry, such as FPGAs and / or ASICs (application specific integrated circuits).

[0052] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, as well as any one or more processors of any kind of digital computer. In general, a processor receives instructions and data from a read only memory or a 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.

[0053] Although several embodiments of the invention are described and illustrated in this specification, those skilled in the art can readily envision various other means and / or structures for obtaining one or more of the advantages described herein and / or for implementing the functions and / or results 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 understand that all parameters, dimensions, materials, and configurations described herein are intended to be exemplary, and that 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 ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Accordingly, the foregoing embodiments are presented by way of example only, and it is to be understood that embodiments of the invention may be practiced otherwise than as specifically described and claimed within the scope of the appended claims and equivalents thereof. Embodiments of the invention disclosed herein are directed to each individual feature, system, article, material, and / or method described herein. Further, any combination of two or more such features, systems, articles, materials, and / or methods is included within the scope of the invention disclosed herein if such features, systems, articles, materials, and / or methods do not mutually conflict.

Claims

1. An LED power supply, comprising: a power factor correction circuit configured to receive an input signal and supply a DC bus voltage across a DC bus; a converter configured to receive the DC bus voltage and output a DC output voltage for supplying power to at least one LED, the converter having a high-side transistor, the high-side transistor being off when the LED power supply is in standby; a voltage sensor configured to output a voltage sensor output, the voltage sensor output being proportional to the DC bus voltage when the high-side transistor is on, and the voltage sensor being arranged in series with the output of the high-side transistor such that the voltage sensor is disconnected from the DC bus when the high-side transistor is off; a controller configured to receive the voltage sensor output and output a control signal according to the voltage sensor output; a peak detector arranged such that the voltage sensor output is proportional to the peak of the DC bus voltage, the LED power supply having the peak detector arranged between the voltage sensor and the output of the high-side transistor.

2. The LED power supply according to claim 1, wherein the peak detector includes a diode and a capacitor.

3. The LED power supply according to claim 1, wherein the controller is configured to average the voltage sensor output.

4. The LED power supply according to claim 1, wherein the controller is configured to sample the voltage sensor output only when the high-side transistor is on.

5. The LED power supply according to claim 1, wherein the controller is configured to output the control signal to the power factor correction circuit according to the voltage sensor output.

6. The LED power supply according to claim 1, wherein the controller is configured to output the control signal to the power factor correction circuit according to the voltage sensor output.

7. The LED power supply according to claim 1, wherein the converter is one of a half-bridge converter, a full-bridge converter, a buck converter, a two-switch flyback converter, or a two-switch forward converter.

8. When the voltage sensor output of the voltage sensor is a current proportional to the DC bus voltage when the high-side transistor is on, and the controller is configured to determine the DC bus voltage according to the current of the voltage sensor output, the LED power supply according to claim 1.

9. When the voltage sensor output of the voltage sensor is a voltage proportional to the DC bus voltage when the high-side transistor is on, and the controller is configured to determine the DC bus voltage according to the voltage sensor output, the LED power supply according to claim 1.

10. The LED power supply according to claim 9, wherein the voltage sensor is a voltage divider.

11. A second voltage sensor configured to output a second voltage sensor output, wherein when the high-side transistor is on, the second voltage sensor output is proportional to the DC bus voltage, and when the high-side transistor is off, the second voltage sensor is arranged in series with the output of the high-side transistor so as to be disconnected from the DC bus. A second voltage sensor, The LED power supply according to claim 1, further comprising a second controller configured to receive the second voltage sensor output and output a second control signal according to the second voltage sensor output.

12. A method for detecting a DC bus in an LED power supply, Receiving an input signal, a power factor correction circuit configured to supply a DC bus voltage across the DC bus, and a converter configured to receive the DC bus voltage and output a DC output voltage for supplying power to at least one LED, wherein the converter has a high-side transistor, and the high-side transistor is off when the LED power supply is in standby. A step of providing a voltage sensor configured to output a voltage sensor output, wherein 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 arranged in series with the output of the high-side transistor so as to be disconnected from the DC bus. A step of detecting the voltage sensor output by a controller, A step of outputting a control signal by the controller according to the voltage sensor output, and A method having a step of providing a peak detector arranged between the voltage sensor and the output of the high-side transistor such that the voltage sensor output is proportional to the peak of the DC bus voltage, wherein the controller is configured to detect the voltage sensor output only when the high-side transistor is on.

13. The method according to claim 12, wherein the control signal is output to the power factor correction circuit.

14. The method according to claim 12, wherein the control signal is output to the converter.

15. The method according to claim 12, wherein the voltage sensor output of the voltage sensor is a current proportional to the DC bus voltage when the high-side transistor is on, and the controller is configured to determine the DC bus voltage according to the current of the voltage sensor output.

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