Power supply device and discharge method thereof

Abstract

The present application provides a power supply device and a discharging method thereof. A control unit detects a cross voltage across an AC safety capacitor to generate a detection voltage, compares the detection voltage with a threshold voltage, counts a number of cycles of the detection voltage during a period when the detection voltage does not cross the threshold voltage according to a comparison result of the detection voltage and the threshold voltage, and performs a discharging action when the number of cycles is greater than or equal to a default value to discharge the energy stored in the AC safety capacitor.

Description

TECHNICAL FIELD

[0001] The present invention relates to an electronic device, and more particularly, to a power supply device and a discharging method thereof. BACKGROUND

[0002] The main purpose of a power supply device is to convert the high-voltage and low-stability AC input power provided by a power company into low-voltage and high-stability DC output power suitable for various electronic devices, such as computers, office automation equipment, industrial control equipment, and communication equipment.

[0003] Most conventional power supply devices are provided with an electromagnetic interference filter (EMI filter) in a front-end stage, and an AC safety capacitor in the EMI filter can be used to filter out noise that may exist in an AC signal. In order to avoid the risk of electric shock, the stored energy of the AC safety capacitor needs to be discharged when the AC power supply of the power supply device is removed or abnormal. The conventional power supply device determines whether to discharge the stored energy of the AC safety capacitor according to whether a sine wave is detected at the input end. Although this method can determine whether the AC power supply is removed, it cannot perform the energy discharge action of the AC safety capacitor when the AC power supply is abnormal and a sine wave is still detected at the input end of the power supply device, thereby causing safety concerns for the power supply device. SUMMARY

[0004] The present invention provides a power supply device that can improve the safety of the power supply device.

[0005] The power supply device of the present invention includes a power conversion circuit, an AC safety capacitor, and a control unit. The power conversion circuit receives an AC input voltage at an input side and converts the AC input voltage into a DC output voltage. The AC safety capacitor is connected across the input side. The control unit is coupled to the power conversion circuit and the AC safety capacitor and controls the operation of the power conversion circuit. The control unit detects a voltage across the AC safety capacitor to generate a detection voltage, compares the detection voltage with a threshold voltage, counts the number of cycles of the detection voltage during a period when the detection voltage and the threshold voltage do not cross over based on the comparison result of the detection voltage and the threshold voltage, and performs a discharging action when the number of cycles is greater than or equal to a default value to discharge the stored energy of the AC safety capacitor.

[0006] In an embodiment of the present invention, the control unit sets the threshold voltage based on the peak voltage of the detection voltage.

[0007] In one embodiment of the present application, the peak voltage of the detection voltage has a default ratio with the threshold voltage, and the control unit sets the threshold voltage according to the peak voltage of the detection voltage and the default ratio.

[0008] In one embodiment of the present application, the control unit sets the threshold voltage of the (N+1)th cycle of the detection voltage according to the peak voltage of the Nth cycle of the detection voltage, where N is a positive integer.

[0009] In one embodiment of the present application, the control unit includes a rectifier circuit, a voltage dividing circuit, a comparator circuit, and a counter circuit. The rectifier circuit is coupled to the power conversion circuit and the AC safety capacitor, and rectifies the AC input voltage to generate a rectified voltage. The voltage dividing circuit is coupled to the rectifier circuit, and divides the rectified voltage to generate the detection voltage. The comparator circuit has positive and negative inputs to receive the threshold voltage and the detection voltage, respectively, and outputs a comparison voltage according to the detection voltage and the threshold voltage. The counter circuit is coupled to the output of the comparator circuit, and generates a count value according to the comparison voltage, the count of the number of cycles of the detection voltage that do not cross the threshold voltage, and outputs a discharge control signal according to the count value and a default value.

[0010] In one embodiment of the present application, the control unit includes a discharge circuit, which is controlled by the discharge control signal to provide a discharge path between the AC safety capacitor and the ground terminal, so as to discharge the electrical energy stored in the AC safety capacitor to the ground terminal.

[0011] In one embodiment of the present application, the discharge circuit includes a controllable load or a voltage-controlled current source.

[0012] In one embodiment of the present application, the power conversion circuit includes an inductor, a full-bridge rectifier circuit, a filter capacitor, and a voltage conversion circuit. The inductor is coupled to the AC safety capacitor, and receives the AC input voltage to filter the power noise in the AC input voltage. The full-bridge rectifier circuit is coupled to the inductor, and full-wave rectifies the AC input voltage filtered by the inductor to generate an input voltage. The filter capacitor is coupled to the full-bridge rectifier circuit, and filters the input voltage. The voltage conversion circuit is coupled to the full-bridge rectifier circuit and the filter capacitor, and is controlled by the control unit to perform voltage conversion on the received input voltage, so as to generate a DC output voltage.

[0013] The present application also provides a discharging method of a power supply device, wherein the power supply device comprises a power conversion circuit and an AC safety capacitor, the power conversion circuit receives an AC input voltage via an input side and converts the AC input voltage into a DC output voltage, the AC safety capacitor is connected across the input side of the power conversion circuit, and the discharging method of the power supply device comprises the following steps. A detection voltage is generated by detecting a voltage across the AC safety capacitor. The detection voltage is compared with a threshold voltage. The number of cycles of the detection voltage during which the detection voltage does not cross the threshold voltage is counted according to the comparison result of the detection voltage and the threshold voltage. When the number of cycles is greater than or equal to a default value, a discharging action is performed to discharge the energy stored in the AC safety capacitor.

[0014] In an embodiment of the present application, the threshold voltage is set according to the peak voltage of the detection voltage.

[0015] In an embodiment of the present application, the peak voltage of the detection voltage and the threshold voltage have a default ratio, and the discharging method of the power supply device comprises setting the threshold voltage according to the peak voltage of the detection voltage and the default ratio.

[0016] In an embodiment of the present application, the threshold voltage corresponding to the (N+1)th cycle of the detection voltage is set according to the peak voltage of the Nth cycle of the detection voltage, wherein N is a positive integer.

[0017] Based on the above, the control unit of the embodiment of the present application detects a voltage across the AC safety capacitor to generate a detection voltage, compares the detection voltage with a threshold voltage, counts the number of cycles of the detection voltage during which the detection voltage does not cross the threshold voltage according to the comparison result of the detection voltage and the threshold voltage, and performs a discharging action when the number of cycles is greater than or equal to a default value to discharge the energy stored in the AC safety capacitor. In this way, the discharging action of the AC safety capacitor can be performed when the AC input voltage is abnormal and a sine wave can still be detected at the input side of the power supply device, thereby improving the safety of the power supply device.

[0018] In order to make the above features and advantages of the present application more apparent, specific embodiments are described below in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A schematic diagram of a power supply device according to an embodiment of the present application;

[0020] Figure 2 A circuit diagram of a power supply device according to an embodiment of the present application;

[0021] Figure 3 A circuit diagram of a control unit according to an embodiment of the present application;

[0022] Figure 4is a timing diagram of the operation of a control unit according to an embodiment of the present application;

[0023] Figure 5 is a timing diagram of the operation of a control unit according to an embodiment of the present application;

[0024] Figure 6 is a flowchart of a discharging method of a power supply device according to an embodiment of the present application. DETAILED DESCRIPTION

[0025] In order that the present application can be more readily understood, the following specific embodiments are given, by way of example, in which like elements / structures / steps are referred to by like reference numerals. Where possible, the same reference numerals are used in the drawings and the specific embodiments to represent the same or similar components.

[0026] Figure 1 is a circuit schematic diagram of a power supply device according to an embodiment of the present application. Please refer to Figure 1 In this embodiment, the power supply device is an AC-DC power supply device, and it comprises a power conversion circuit 110, an AC safety capacitor C, and a control unit 120. The AC safety capacitor C is connected across the input side IS, and the control unit 120 is coupled to the power conversion circuit 110 and the AC safety capacitor C. The power conversion circuit 110 receives an AC input voltage AC IN (for example, mains power, i.e. a sinusoidal waveform with a frequency of 60 Hz, but this is not limiting) via the input side IS, and converts the AC input voltage AC IN to a DC output voltage DC OUT which is output to a load via the output side OS. In this embodiment, the power conversion circuit 110 can be a full bridge power converter, and can comprise a full-bridge rectifier for full-wave rectification, and a filter capacitor for filtering the output of the full-bridge rectifier. In other embodiments, other types of power converter can be used in the present application, for example a half bridge power converter, a Forward power converter, a Flyback power converter, or a Push-Pull power converter, and the embodiments of the present application are not limited in terms of the type of power conversion circuit.

[0027] The AC safety capacitor C is used to filter / suppress noise that may exist in the AC input voltage AC_IN. The control unit 120 is, for example, a pulse width modulation (PWM) control chip, which can be used to control the operation of the power conversion circuit 110. In this embodiment, the control unit 120 can detect the voltage across the AC safety capacitor C to generate a detection voltage, compare the detection voltage with a threshold voltage, and determine whether the detection voltage and the threshold voltage have crossed based on the comparison result. When the detection voltage and the threshold voltage have not crossed, the number of detection voltage cycles during the period when the detection voltage and the threshold voltage have not crossed is counted, and a discharge action is performed when the number of cycles is greater than or equal to a default value to release the electrical energy stored in the AC safety capacitor C. The control unit 120 can set a threshold voltage based on the peak voltage of the detected voltage. For example, there may be a default ratio between the peak voltage of the detected voltage and the threshold voltage. The control unit 120 can set the threshold voltage based on the peak voltage of the detected voltage and the default ratio. For example, the threshold voltage can be set to 20% of the peak voltage of the detected voltage when the AC input voltage AC_IN is operating normally. However, this is not a limitation. In other embodiments, the threshold voltage can be set to 30% of the peak voltage of the detected voltage or other ratios depending on the application. When the AC input voltage AC_IN is operating normally, the detected voltage will continuously cross the threshold voltage. When the AC input voltage AC_IN is removed or an abnormality occurs (e.g., one end of the input side IS becomes floating), the amplitude of the detected voltage will disappear or decrease, and the crossover between the detected voltage and the threshold voltage will disappear. Therefore, the control unit 120 determines whether to perform a discharge operation based on whether the detected voltage and the threshold voltage cross. Even if the AC input voltage AC_IN is abnormal but a sine wave can still be detected at the input of the power supply device, the control unit 120 will automatically perform a discharge operation, thus ensuring the safety of the power supply device.

[0028] Figure 2 This is a schematic diagram of a power supply device according to another embodiment of the present invention. Please refer to... Figure 2 The power supply device includes a power conversion circuit 210, an AC safety capacitor C, and a control unit 220. In this embodiment, the power conversion circuit 210 includes a choke coil L, a full-bridge rectifier circuit (e.g., composed of diodes D3 to D6), a filter capacitor C1, and a transformer conversion circuit (e.g., composed of a power switch Q, a transformer T, a diode D7, capacitors C2 and C3, and a resistor R4).

[0029] The anti-current coil L, for example, has two conjugate coils. The two conjugate coils are coupled across the AC safety capacitor C and receive the AC input voltage AC_IN, wherein the anti-current coil L can be used to filter power supply noise input to the power conversion circuit 210.

[0030] The full-bridge rectifier circuit composed of diodes D3-D6 is coupled to the choke L, wherein the cathode of diode D3 and the anode of diode D4 are coupled together to one of the conjugate coils of the choke L, and the cathode of diode D5 and the anode of diode D6 are coupled together to the other of the conjugate coils of the choke L. The full-bridge rectifier circuit is used to receive the noise-suppressed AC voltage AC_IN and to perform full-wave rectification thereon to generate the input voltage Vin. The first end of the filter capacitor Cl is coupled to the cathodes of diodes D4 and D6, and the second end of the filter capacitor Cl is coupled to the second ground terminal Vref2. The filter capacitor Cl is used to filter the input voltage Vin generated by the full-bridge rectifier circuit.

[0031] In the voltage conversion circuit, the transformer T has a primary side PS and a secondary side SS. The same terminal (the dot terminal) of the primary side PS of the transformer T is coupled to the first end of the filter capacitor Cl to receive the input voltage Vin. The power switch Q, for example, is an N-type transistor, and its first end (the drain terminal) is coupled to the different terminal (the non-dot terminal) of the primary side PS of the transformer T and is switched under the control of the driving signal Vpwm generated by the control unit 220. The anode of diode D7 is coupled to the different terminal of the secondary side SS of the transformer T. In addition, the first end of capacitor C2 is coupled to the cathode of diode D7, and the second end of capacitor C2 is coupled together with the same terminal of the secondary side SS of the transformer T to the first ground terminal Vrefl. The resistor R4 and the capacitor C3 are connected in series across the two ends of diode D7. Thus, the transformer T will react to the switching of the power switch Q and the turns ratio of the primary side PS and the secondary side SS coils to induce an induced voltage associated with the input voltage Vin at the secondary side SS. The induced voltage will then be converted into a DC output voltage DC_OUT through the actions of diode D7, resistor R4, and capacitors C2 and C3. In other words, the voltage conversion circuit can react to the driving signal Vpwm to convert the output of the filter capacitor Cl into the DC output voltage DC_OUT through voltage transformation.

[0032] As for the control unit 220, in the present embodiment, it can include a control chip 221 and a rectifier circuit 222. The rectifier circuit 222 is coupled to the power conversion circuit 210 and the AC safety capacitor C and performs rectification on the AC input voltage AC_IN to generate a rectified voltage Vrec. In the present embodiment, the rectifier circuit 222 can be a half- wave rectifier circuit composed of diodes Dl and D2, and the anodes of diodes Dl and D2 are used to receive the AC input voltage AC_IN, and the cathodes of diodes Dl and D2 are used to provide the rectified voltage Vrec.

[0033] The control chip 221 has a plurality of pins for receiving or outputting signals, such as a power pin VCC, a ground pin GND, a high voltage pin HV, an output pin DRV, a feedback pin VFB, a current sensing pin CS, an AC power detection pin AC_DET, and the like. The control chip 221 can receive an operating voltage required by the control chip 221 via the power pin VCC and be coupled to the second ground terminal Vref2 through the ground pin GND, so that the control chip 221 can normally operate and can adjust the received operating voltage to generate an operating voltage required by each functional circuit in the control chip 221. In the embodiment, the control chip 221 can receive a rectified voltage Vrec associated with the AC input voltage AC_IN via the high voltage pin HV and adjust the rectified voltage Vrec via an internal circuit of the control chip 221 to serve as an operating voltage thereof. In other embodiments, the control chip 221 can also receive an external DC input voltage as an operating voltage thereof. The bypass capacitor C4 is coupled between the power pin VCC and the second ground terminal Vref2 of the control chip 221 to reduce power noise input to the control chip 221, thereby stabilizing the operation of the control chip 221. The bypass capacitor C4 can be selected according to design requirements.

[0034] The control unit 220 can generate and output the above-mentioned drive signal Vpwm via the output pin DRV of the control chip 221 to control the switching of the power switch Q, so that the voltage conversion circuit 210 outputs the DC output voltage DC_OUT. The feedback pin VFB of the control chip 221 can be coupled to the secondary side SS of the transformer T via a feedback circuit (not shown), wherein the feedback circuit is used to receive the DC output voltage DC_OUT and provide a feedback signal Vfb associated with the state of the load terminal to the feedback pin VFB of the control chip 221. It is worth mentioning that any circuit type (such as a feedback circuit using a resistance voltage divider) that can output a feedback signal associated with the state of the load terminal can be used as the feedback circuit of the embodiment, and thus the embodiment does not limit the implementation of the feedback circuit.

[0035] As for the current sensing pin CS of the control chip 221, the current flowing through the power switch Q can be detected by using the resistor R3 coupled between the second terminal of the power switch Q and the second ground terminal Vref2. Based on actual design or application requirements, the control chip 221 can be additionally provided with other functional pins, such as an overvoltage detection pin, an overcurrent detection pin, and the like, or the existing functional pins of the control chip 221 can be deleted, and the present application does not limit this.

[0036] In the present embodiment, the control unit 200 further comprises a voltage dividing circuit composed of resistors Rl and R2. The voltage dividing circuit is coupled between the rectifier circuit 222 and the second ground terminal Vref2, and is used to divide the rectified voltage Vrec to generate a detection voltage VD and provide the detection voltage VD to the AC power detection pin AC_DET of the control chip 221. The control chip 221 can determine whether to perform the discharging action according to whether the detection voltage VD crosses the threshold voltage. Thus, even if the AC input voltage AC_IN is abnormal, the control chip 221 can automatically perform the discharging action when a sine wave is detected at the input terminal of the power supply device, thereby improving the safety of the power supply device.

[0037] In order to more clearly illustrate the specific architecture and operation of the control unit in the embodiments of the present application, the following examples are used to illustrate the specific architecture and operation of the control unit in the embodiments of the present application, wherein, Figures 3 to 5 Figure 3 is a circuit diagram of the control unit 220 according to an embodiment of the present application, and Figure 4 Figure 5 is a timing diagram of the control unit 220 according to an embodiment of the present application.

[0038] Please refer to Figure 3 , the control unit 220 can comprise a comparator circuit 302 and a counter circuit 304. The positive input terminal of the comparator circuit 302 receives a threshold voltage Vlow, and the negative input terminal of the comparator circuit 302 receives a detection voltage VD through the AC power detection pin AC_DET. The output terminal of the comparator circuit 302 is coupled to the counter circuit 304. The comparator circuit 302 can compare the detection voltage VD with the threshold voltage Vlow to generate a comparison voltage VC for the counter circuit 304. The counter circuit 304 can count the number of cycles of the detection voltage VD during which the detection voltage VD does not cross the threshold voltage Vlow according to the comparison voltage VC, and output a discharging control signal SD according to the count value and a default value.

[0039] For example, as shown in Figure 4 , the detection voltage VD has a peak voltage VP and a valley voltage VV. When the AC input voltage AC_IN is normal, the threshold voltage Vlow (which can be, for example, 20% of the peak voltage VP of the detection voltage VD when the AC input voltage AC_IN is normal, but is not limited thereto) periodically crosses the detection voltage VD. Correspondingly, the comparison voltage VC output by the comparator circuit 302 also periodically changes its voltage level. The counter circuit 304 can determine that no discharging action is needed at this time according to the comparison voltage VC, and thus the discharging control signal SD is maintained at a low voltage level.

[0040] In addition, as shown in Figure 5 ​​As shown, in the case of abnormal AC input voltage AC_IN, the detection voltage VD will react the case of amplitude reduction of the change of AC input voltage AC_IN, at this time the threshold voltage Vlow continuously lower than the detection voltage VD, thus the threshold voltage Vlow and the detection voltage VD no longer cross, the comparison voltage VC outputted by the comparator circuit 302 also continuously maintains at the low voltage level. The counter circuit 304 can start counting the detection voltage VD after the first cycle of the detection voltage VD ends. As shown, Figure 5 As shown, assuming the above-mentioned default value is 10, since the comparison voltage VC continuously maintains at the low voltage level, the counter circuit 304 continuously counts the number of cycles of the detection voltage VD, and outputs the discharge control signal SD at the high voltage level after counting 10 cycles of the detection voltage VD, to perform the discharge action.

[0041] It is worth noting that in some embodiments, the control unit 220 can also set the threshold voltage Vlow corresponding to the N+1 cycle of the detection voltage VD according to the peak voltage VP of the N cycle of the detection voltage VD, wherein N is a positive integer, for example, 20% of the peak voltage VP of the N cycle of the detection voltage VD can be set as the threshold voltage Vlow of the N+1 cycle of the detection voltage VD, but not limited thereto. That is, the threshold voltage Vlow can vary with the peak voltage VP of the last cycle of the detection voltage VD, and is not limited to 20% of the peak voltage VP under normal operation of the AC input voltage AC_IN.

[0042] For the description of the discharge circuit, please refer to Figure 2 The discharge circuit 229 can be enabled (for example, at the high voltage level) or disabled (for example, at the low voltage level) according to the discharge control signal SD, and correspondingly determine whether to conduct a discharge path between the AC safety capacitor C and the second ground terminal Vref2, thereby discharging the electrical energy stored in the AC safety capacitor C. The discharge path can be realized by a controllable load (for example, a combination circuit composed of a switch and a resistor connected in series) coupled between the high voltage pin HV and the second ground terminal Vref, but the present application is not limited thereto. In another embodiment, the discharge circuit 229 can also be realized by a voltage-controlled current source. The present application does not limit the controllable load and the circuit implementation of how to discharge the electrical energy stored in the AC safety capacitor C.

[0043] Figure 6A flowchart of a discharging method of a power supply device according to an embodiment of the present application. As can be seen from the above embodiment, the discharging method of the power supply device can include at least the following steps. First, a cross voltage across the AC safety capacitor is detected to generate a detection voltage (step S602). Then, the detection voltage is compared with a threshold voltage (step S604) to determine whether the detection voltage and the threshold voltage cross over according to a comparison result of the detection voltage and the threshold voltage, wherein the threshold voltage can be set according to a peak voltage of the detection voltage, for example, the peak voltage of the detection voltage and the threshold voltage can have a default ratio, the threshold voltage can be set according to the peak voltage of the detection voltage and the default ratio, for example, the threshold voltage is set as 20% of the peak voltage of the detection voltage, but not limited thereto. In some embodiments, the threshold voltage of an N+1 period of the detection voltage can be set according to a peak voltage of an N period of the detection voltage. Thereafter, the number of periods of the detection voltage during which the detection voltage and the threshold voltage do not cross over is counted according to the comparison result of the detection voltage and the threshold voltage (step S606), and when the number of periods is greater than or equal to a default value, a discharging action is performed to discharge the energy stored in the AC safety capacitor.

[0044] In summary, the control unit of the embodiment of the present application detects a cross voltage across the AC safety capacitor to generate a detection voltage, compares the detection voltage with a threshold voltage, counts the number of periods of the detection voltage during which the detection voltage and the threshold voltage do not cross over according to the comparison result of the detection voltage and the threshold voltage, and when the number of periods is greater than or equal to a default value, a discharging action is performed to discharge the energy stored in the AC safety capacitor. In this way, the discharging action of the AC safety capacitor can be performed when the AC input voltage is abnormal and a sine wave can still be detected at the input of the power supply device, thereby improving the use safety of the power supply device.

[0045] Although the present application has been disclosed with embodiments as above, it is not intended to limit the present application, and any person skilled in the art can make some changes and modifications without departing from the spirit and scope of the present application, therefore the protection scope of the present application shall be subject to the claims.

Claims

1. A power supply device, characterized in that, include: The power conversion circuit receives AC input voltage via the input side and converts the AC input voltage into DC output voltage; An AC safety capacitor is connected across the input side; as well as A control unit, coupled to the power conversion circuit and the AC safety capacitor, controls the operation of the power conversion circuit. The control unit detects the voltage across the AC safety capacitor to generate a detection voltage, compares the detection voltage with a threshold voltage, and counts the number of cycles of the detection voltage during the period when the detection voltage and the threshold voltage do not cross, based on the comparison result of the detection voltage and the threshold voltage, when the number of cycles is greater than or equal to a default value, performs a discharge action to release the electrical energy stored in the AC safety capacitor.

2. The power supply device according to claim 1, characterized in that, The control unit sets the threshold voltage based on the peak voltage of the detected voltage.

3. The power supply device according to claim 1, characterized in that, The peak voltage of the detection voltage has a default ratio with respect to the threshold voltage, and the control unit sets the threshold voltage based on the peak voltage of the detection voltage and the default ratio.

4. The power supply device according to claim 1, characterized in that, The control unit sets the threshold voltage for the (N+1)th cycle of the detection voltage based on the peak voltage of the Nth cycle of the detection voltage, where N is a positive integer.

5. The power supply device according to claim 1, characterized in that, The control unit includes: A rectifier circuit, coupled to the power conversion circuit and the AC safety capacitor, rectifies the AC input voltage to generate a rectified voltage. A voltage divider circuit is coupled to the rectifier circuit to divide the rectified voltage and generate the detection voltage. A comparator circuit receives the threshold voltage and the detection voltage at its positive and negative input terminals, respectively, and outputs a comparison voltage based on the detection voltage and the threshold voltage; and A counter circuit, coupled to the output of the comparator circuit, generates a count value by counting the number of cycles of the detection voltage that do not intersect with the threshold voltage based on the comparison voltage, and outputs a discharge control signal based on the count value and the default value.

6. The power supply device according to claim 1, characterized in that, The control unit includes: The discharge circuit, controlled by a discharge control signal, provides a discharge path between the AC safety capacitor and the ground terminal to discharge the electrical energy stored in the AC safety capacitor to the ground terminal.

7. The power supply device according to claim 6, characterized in that, The discharge circuit includes a controllable load or a voltage-controlled current source.

8. The power supply device according to claim 1, characterized in that, The power conversion circuit includes: An anti-current coil, coupled to the AC safety capacitor, receives the AC input voltage and is used to filter power supply noise in the AC input voltage; A full-bridge rectifier circuit, coupled to the anti-current coil, performs full-wave rectification on the AC input voltage filtered by the anti-current coil to generate an input voltage; A filter capacitor, coupled to the full-bridge rectifier circuit, is used to filter the input voltage; and The transformer circuit, coupled to the full-bridge rectifier circuit and the filter capacitor, is controlled by the control unit to transform the received input voltage to generate the DC output voltage.

9. A method for discharging a power supply device, characterized in that, The power supply device includes a power conversion circuit and an AC safety capacitor. The power conversion circuit receives an AC input voltage via its input side and converts the AC input voltage into a DC output voltage. The AC safety capacitor is connected across the input side of the power conversion circuit. The discharge method of the power supply device includes: The voltage across the AC safety capacitor is detected to generate a detection voltage; Compare the detected voltage with the threshold voltage; When the detected voltage is still a sine wave, the number of periods during which the detected voltage and the threshold voltage do not cross is counted based on the comparison result between the detected voltage and the threshold voltage; and When the number of cycles is greater than or equal to the default value, a discharge action is performed to release the electrical energy stored in the AC safety capacitor.

10. The discharge method of the power supply device according to claim 9, characterized in that, The threshold voltage is set based on the peak voltage of the detected voltage.

11. The discharge method of the power supply device according to claim 9, characterized in that, The peak voltage of the detected voltage has a default ratio with respect to the threshold voltage, and the discharge method of the power supply device includes: The threshold voltage is set based on the peak voltage of the detected voltage and the default ratio.

12. The discharge method of the power supply device according to claim 9, characterized in that, The threshold voltage corresponding to the (N+1)th cycle of the detection voltage is set based on the peak voltage of the Nth cycle of the detection voltage, where N is a positive integer.

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