Power conversion device and control circuit

Abstract

The present application provides a power conversion device and a control circuit. The power conversion device includes a power conversion circuit and a control circuit. The control circuit includes a first controller and a second controller. The power conversion circuit includes an input capacitor, a rectification circuit and a power switch. The input capacitor is coupled to an input terminal of the power conversion device. The rectification circuit converts an input AC power into a rectified power. The first controller operates the power switch so that the power conversion circuit converts the rectified power into an output power. The second controller detects a signal waveform at the input terminal and controls the first controller in response to the signal waveform at the input terminal so that the power switch discharges a charge stored in the input capacitor.

Description

Technical Field

[0001] This invention relates to a power conversion device and a control circuit, and more particularly to a power conversion device and a control circuit capable of discharging the charge stored in an input capacitor. Background Technology

[0002] Modern power converters are trending towards miniaturization. They typically have only two input pins. An input capacitor (or safety capacitor) is positioned between these two input pins. Due to the demands of high-voltage applications, the input capacitor's discharge capability is essential.

[0003] To enable the power converter to discharge its input capacitor, the power converter includes a discharge resistor. This discharge resistor is connected in parallel with the input capacitor. The discharge resistor is used to release the charge stored in the input capacitor. Therefore, when the power converter is disconnected from the input power supply, the discharge resistor reduces the risk of electric shock to the user from touching the input terminal of the power converter.

[0004] However, the configuration of the discharge resistor will cause the power conversion device to generate a predetermined power consumption. This power consumption will inevitably affect the efficiency and power factor of the power conversion device. Therefore, providing an input capacitor discharge function that differs from that of a discharge resistor is one of the research focuses of those skilled in the art. Summary of the Invention

[0005] The present invention provides a power conversion device and a control circuit capable of discharging the charge stored in the input capacitor.

[0006] The power conversion device of the present invention includes a power conversion circuit and a control circuit. The control circuit includes a first controller and a second controller. The power conversion circuit includes an input capacitor, a rectifier circuit, and a power switch. The input capacitor is coupled to the input terminal of the power conversion device. The rectifier circuit is coupled to the input terminal. The rectifier circuit converts the input AC power into rectified power. A first terminal of the power switch is coupled to the rectifier circuit. The first controller is coupled to the control terminal of the power switch. The first controller operates the power switch, thereby causing the power conversion circuit to convert the rectified power into output power. The second controller is coupled to the input terminal and the first controller. The second controller detects the signal waveform at the input terminal and controls the first controller based on the signal waveform at the input terminal, thereby using the power switch to discharge the charge stored in the input capacitor.

[0007] The control circuit of this invention is used to control a power conversion circuit. The power conversion circuit includes an input capacitor, a rectifier circuit, and a power switch. The input capacitor is coupled to the input terminal of the power conversion device. The rectifier circuit converts the input AC power into rectified power. A first terminal of the power switch is coupled to the rectifier circuit. The control circuit includes a first controller and a second controller. The first controller is coupled to the control terminal of the power switch. The first controller operates the power switch, thereby causing the power conversion circuit to convert the rectified power into output power. The second controller is coupled to the input terminal and the first controller. The second controller detects the signal waveform at the input terminal and controls the first controller based on the signal waveform at the input terminal, thereby using the power switch to discharge the charge stored in the input capacitor.

[0008] Based on the above, the second controller detects the signal waveform at the input terminal and controls the first controller accordingly, thereby using a power switch to discharge the charge stored in the input capacitor. Compared to existing input capacitor discharge functions, this invention reduces power consumption while maintaining high efficiency and a high power factor in the power conversion device.

[0009] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of a power conversion device according to the first embodiment of the present invention;

[0011] Figure 2 This is a schematic diagram of a power conversion device according to a second embodiment of the present invention;

[0012] Figure 3 This is a schematic diagram of a discharge control circuit and a first controller according to an embodiment of the present invention;

[0013] Figure 4 This is a schematic diagram of a power conversion device according to a third embodiment of the present invention;

[0014] Figure 5 This is a schematic diagram of a first controller according to an embodiment of the present invention;

[0015] Figure 6 This is a schematic diagram of a power conversion device according to the fourth embodiment of the present invention.

[0016] Explanation of reference numerals in the attached figures

[0017] 100, 200, 300, 400: Power conversion devices

[0018] 110, 210: Power conversion circuit

[0019] 120, 220, 320: Control circuit

[0020] 121, 221, 321: First controller

[0021] 122, 222, 322: Second controller

[0022] 211, 411: Current sensing circuit

[0023] 2221, 3221: Detection circuit

[0024] 2222: Discharge control circuit

[0025] CO: Output capacitor

[0026] CR: Rectifier capacitor

[0027] CX: Input capacitor

[0028] DO: Output diode

[0029] DRV: Drive

[0030] FBC: Full-bridge rectifier circuit

[0031] LDIS: Discharge Circuit

[0032] LB: Boost Inductor

[0033] OP: Operational amplifier

[0034] RC: Rectifier circuit

[0035] RCS: Sensing Resistor

[0036] SCS: Feedback Signal

[0037] SD, SD1, SD2: Drive signals

[0038] SP: Power Switch

[0039] SPWM: Pulse Width Modulation Signal

[0040] SREF: Reference Signal

[0041] SSX: Status Signal

[0042] SSXB: Complementary State Signal

[0043] VAC: Input AC power

[0044] VOUT: Output power

[0045] VR: Rectified power supply Detailed Implementation

[0046] Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same component reference numerals are used in the drawings and description to denote the same or similar parts.

[0047] Please refer to Figure 1 , Figure 1 This is a schematic diagram of a power conversion device according to a first embodiment of the present invention. In this embodiment, the power conversion device 100 includes a power conversion circuit 110 and a control circuit 120. The power conversion circuit 110 includes at least an input capacitor CX, a rectifier circuit RC, and a power switch SP. The input capacitor CX is coupled to the input terminal of the power conversion device 100. In this embodiment, the input capacitor CX is a safety capacitor, such as an X capacitor. The input capacitor CX is coupled between two input pins of the input terminal. The rectifier circuit RC is coupled to the input terminal. The rectifier circuit RC converts the input AC power VAC into rectified power VR. The first terminal of the power switch SP is coupled to the rectifier circuit RC. The second terminal of the power switch SP is coupled to a reference low voltage (e.g., ground).

[0048] In this embodiment, the control circuit 120 includes a first controller 121 and a second controller 122. The first controller 121 is coupled to the control terminal of the power switch SP. The first controller 121 operates the power switch SP, thereby causing the power conversion circuit 110 to convert the rectified power supply VR into the output power supply VOUT. The second controller 122 is coupled to the input terminal and the first controller 121. The second controller 122 detects the signal waveform at the input terminal. The second controller 122 also controls the first controller 121 in response to the signal waveform at the input terminal, thereby using the power switch SP to discharge the charge stored in the input capacitor CX.

[0049] It is worth mentioning that the second controller 122 detects the signal waveform at the input terminal and controls the first controller 121 accordingly, thereby using the power switch SP to discharge the charge stored in the input capacitor CX. In this way, compared to the existing input capacitor discharge function, the control circuit 120 can reduce power consumption and maintain the high efficiency and high power factor of the power conversion device 100. Furthermore, the power conversion circuit 110 discharges the charge stored in the input capacitor CX through its own existing loop or power conversion function. Therefore, the design of the power conversion circuit 110 does not need to be changed.

[0050] In this embodiment, the power conversion circuit 110 is implemented, for example, by a boost power conversion circuit. The power conversion circuit 110 also includes a boost inductor LB, an output diode DO, and an output capacitor CO. The boost inductor LB is coupled between the rectifier circuit RC and the first terminal of the power switch SP. The anode of the output diode DO is coupled to the first terminal of the power switch SP. The cathode of the output diode DO serves as the output terminal of the power conversion circuit 110. The output capacitor CO is coupled between the cathode of the output diode DO and a reference low voltage. In this embodiment, the rectifier circuit RC includes, for example, a full-bridge rectifier circuit FBC and a rectifier capacitor CR. The power conversion circuit of the present invention is not limited to this embodiment. In some embodiments, the power conversion circuit 110 may be implemented by a rectifier circuit RC and a power conversion circuit with a power switch. The power conversion circuit may be, for example, a flyback converter, a buck power conversion circuit, or an LLC resonant converter.

[0051] Please refer to Figure 2 , Figure 2 This is a schematic diagram of a power conversion device according to a second embodiment of the present invention. In this embodiment, the power conversion device 200 includes a power conversion circuit 210 and a control circuit 220. The power conversion circuit 210 includes an input capacitor CX, a rectifier circuit RC, a power switch SP, a boost inductor LB, an output diode DO, an output capacitor CO, and a current sensing circuit 211. The input capacitor CX is coupled to the input terminal of the power conversion device 200. In this embodiment, the input capacitor CX is a safety capacitor, such as an X capacitor. The input capacitor CX is coupled between two input pins of the input terminal. The rectifier circuit RC is coupled to the input terminal. The rectifier circuit RC converts the input AC power VAC into rectified power VR. The first terminal of the power switch SP is coupled to the rectifier circuit RC. The boost inductor LB is coupled between the rectifier circuit RC and the first terminal of the power switch SP. The current sensing circuit 211 is coupled between the second terminal of the power switch SP and a reference low voltage. The current sensing circuit 211 provides a feedback signal SCS in response to the current value flowing through the power switch SP. In other words, the power conversion circuit provides the feedback signal SCS based on the current value flowing through the power switch SP. The anode of the output diode DO is coupled to the first terminal of the power switch SP. The cathode of the output diode DO serves as the output terminal of the power conversion circuit 210. The output capacitor CO is coupled between the cathode of the output diode DO and a reference low voltage.

[0052] In this embodiment, the control circuit 220 includes a first controller 221 and a second controller 222. The first controller 221 is coupled to the current sensing circuit 211 and the power switch SP. The first controller 221 generates a drive signal SD1 in response to a pulse-width modulation (PWM) signal SPWM. The duty cycle of the drive signal SD1 is determined by the pulse width of the PWM signal SPWM. The power switch SP operates in response to the drive signal SD1. Therefore, based on the drive signal SD1, the power conversion circuit 210 converts the rectified power supply VR into the output power supply VOUT. Furthermore, the first controller 221 adjusts the duty cycle of the drive signal SD1 according to the feedback signal SCS. Therefore, the first controller 221 can support constant current control of the power conversion circuit 210. For example, the current sensing circuit 211 includes a sensing resistor RCS (this invention is not limited thereto). The sensing resistor RCS is coupled between the second terminal of the power switch SP and a reference low voltage. The current sensing circuit 211 converts the current flowing through the power switch SP into a feedback signal SCS. Therefore, the voltage value of the feedback signal SCS is positively correlated with the current flowing through the power switch SP. When the voltage value of the feedback signal SCS rises to a first preset voltage value, the first controller 221 reduces the duty cycle of the drive signal SD1. Conversely, when the voltage value of the feedback signal SCS drops to a second preset voltage value, the first controller 221 increases the duty cycle of the drive signal SD1. In this embodiment, the first preset voltage value is set to be greater than or equal to the second preset voltage value.

[0053] In this embodiment, the second controller 222 includes a detection circuit 2221 and a discharge control circuit 2222. The detection circuit 2221 is coupled to the input terminal. The detection circuit 2221 detects the signal waveform at the input terminal and generates a status signal based on the signal waveform at the input terminal. When the waveform of the input AC power supply VAC is detected, this indicates that the power conversion device 200 is connected to the input AC power supply VAC. Therefore, the detection circuit 2221 generates a status signal SSX with a first voltage value. On the other hand, when the waveform of the input AC power supply VAC is not detected within a preset time length, this indicates that the power conversion device 200 has disconnected from the input AC power supply VAC. Therefore, the detection circuit 2221 generates a status signal SSX with a second voltage value. The first voltage value is different from the second voltage value. For example, the first voltage value is a low voltage value, and the second voltage value is a high voltage value.

[0054] It should be noted that the aforementioned preset time length is equal to multiple cycles of the input AC power supply VAC. That is, the detection circuit 2221 will only generate a status signal SSX with a second voltage value if it fails to detect a voltage sine wave waveform of the input AC power supply VAC within these multiple cycles. In this way, malfunctions caused by the unstable instantaneous input AC power supply VAC in the control circuit 220 are avoided.

[0055] In this embodiment, the status signal SSX can be a flag signal. The first voltage value corresponds to a first status flag value. The second voltage value corresponds to a second status flag value that is different from the first status flag value.

[0056] In this embodiment, the discharge control circuit 2222 is coupled to the detection circuit 2221 and the first controller 221. The discharge control circuit 2222 is disabled in response to a state signal SSX having a first voltage value. The discharge control circuit 2222 is enabled in response to a state signal SSX having a second voltage value to control the power switch SP, thereby discharging the charge stored in the input capacitor CX. The discharge control circuit 2222 provides a drive signal SD2 to control the power switch SP to release the charge stored in the input capacitor CX.

[0057] In other words, when the power conversion device 200 is connected to the input AC power supply VAC, the second controller 222 responds to the status signal SSX with a first voltage value to disable the discharge control circuit 2222. The power conversion circuit 210 converts the rectified power supply VR into the output power supply VOUT. When the power conversion device 200 is disconnected from the input AC power supply VAC, the second controller 222 responds to the status signal SSX with a second voltage value to disable the first controller 221. Furthermore, the second controller 222 also responds to the status signal SSX with a second voltage value to control the power switch SP, thereby allowing the charge stored in the input capacitor CX to flow through the first terminal and the second terminal of the power switch SP. In this way, the power conversion device 200 can release the charge stored in the input capacitor CX to the reference low voltage through the boost inductor LB and the discharge circuit LDIS of the power switch SP.

[0058] Please refer to Figure 2 as well as Figure 3 , Figure 3This is a schematic diagram of a discharge control circuit and a first controller according to an embodiment of the present invention. The first controller 221 includes a driver DRV. The driver DRV responds to a complementary state signal SSXB by generating a drive signal SD1 using a pulse width modulation signal SPWM. In this embodiment, the driver DRV can be implemented by a buffer or a follower. In this embodiment, the discharge control circuit 2222 includes an operational amplifier OP. The operational amplifier OP is coupled to a power switch SP and a detection circuit 2211. The operational amplifier OP is enabled in response to a state signal SSX having a second voltage value and controls the power switch SP based on a comparison between a feedback signal SCS and a reference signal SREF. The operational amplifier OP is disabled in response to a state signal SSX having a first voltage value. In this embodiment, the reference signal SREF is a voltage signal having a preset voltage value.

[0059] In this embodiment, the complementary state signal SSXB is an inverse of the state signal SSX. The first controller 221 receives the state signal SSX and uses an inverter (not shown) to invert the state signal SSX to generate the complementary state signal SSXB. When the state signal SSX has a first voltage value, the driver DRV is enabled based on the complementary state signal SSXB having a second voltage value to generate the drive signal SD1. The operational amplifier OP is disabled in response to the state signal SSX having the first voltage value and stops generating the drive signal SD2. When the state signal SSX has a second voltage value, the driver DRV is disabled based on the complementary state signal SSXB having the first voltage value. For example, the driver DRV is disabled to enter a high-impedance (Hi-Z) state to stop generating the drive signal SD1. The operational amplifier OP is enabled in response to the state signal SSX having the second voltage value to generate the drive signal SD2.

[0060] In this embodiment, the operational amplifier OP has an inverting input, a non-inverting input, and an output. The inverting input of the operational amplifier OP receives the feedback signal SCS. The non-inverting input of the operational amplifier OP receives the reference signal SREF. The output of the operational amplifier OP is coupled to the control terminal of the power switch SP. The operational amplifier OP compares the voltage value of the feedback signal SCS with the reference voltage value of the reference signal SREF. The reference voltage value of the reference signal SREF is constant. The operational amplifier OP and the power switch SP together form a voltage regulation circuit, such as a low dropout (LDO) regulation circuit. When the voltage value of the feedback signal SCS is higher than the reference voltage value of the reference signal SREF, the operational amplifier OP decreases the level of the drive signal SD2. When the voltage value of the feedback signal SCS is lower than or equal to the reference voltage value of the reference signal SREF, the operational amplifier OP increases the level of the drive signal SD2. In this way, the operational amplifier OP can provide a stable input capacitor discharge function. The discharge current value on the discharge circuit LDIS is approximately constant.

[0061] Please refer to Figure 4 , Figure 4 This is a schematic diagram of a power conversion device according to a third embodiment of the present invention. In this embodiment, the power conversion device 300 includes a power conversion circuit 210 and a control circuit 320. The configuration of the power conversion circuit 210 has already been described. Figure 2 The embodiments are clearly illustrated and will not be repeated here. In this embodiment, the control circuit 320 includes a first controller 321 and a second controller 322. The second controller 322 detects the signal waveform at the input terminal of the power conversion device 300 to determine whether the power conversion circuit 210 receives the input AC power VAC. When the power conversion circuit 210 does not receive the input AC power VAC, the second controller 322 controls the first controller 321 to cause the power conversion circuit 210 to convert the charge stored in the input capacitor CX into the output power VOUT, thereby consuming the charge stored in the input capacitor CX. In this way, the power conversion device 300 can release the charge stored in the input capacitor CX through the boost inductor LB, the output diode DO, and the discharge circuit LDIS at the output terminal of the power conversion device 300.

[0062] In this embodiment, the second controller 322 includes a detection circuit 3221. The detection circuit 3221 is coupled to the input terminal to detect the signal waveform at the input terminal of the power conversion device 300. When the waveform of the input AC power supply VAC is detected, the detection circuit 3221 generates a status signal SSX with a first voltage value. On the other hand, when the waveform of the input AC power supply VAC is not detected within a preset time period, the detection circuit 3221 generates a status signal SSX with a second voltage value. Based on the control of the second controller 322, the first controller 321 generates a pulse width modulation signal SPWM according to the fluctuation of the feedback signal SCS and the second voltage value of the status signal SSX. The first controller 321 also generates a drive signal SD according to the pulse width modulation signal SPWM and provides the drive signal SD to the control terminal of the power switch SP. The duty cycle of the drive signal SD is related to the voltage value of the feedback signal SCS. In this way, the first controller 321 can provide a stable input capacitor discharge function. The discharge energy on the discharge circuit LDIS is approximately constant.

[0063] Please also refer to Figure 4 as well as Figure 5 , Figure 5 This is a schematic diagram of a first controller according to an embodiment of the present invention. The first controller 321 includes a pulse width modulation (PWM) signal generator 3211 and a driver DRV. The PWM signal generator 3211 is coupled to a second controller 322 and a current sensing circuit 211. The PWM signal generator 3211 receives a status signal SSX from a detection circuit 3221 and a feedback signal SCS from the current sensing circuit 211. When the status signal SSX with a first voltage value (low voltage value) is received, the PWM signal generator 3211 generates a PWM signal SPWM based on the voltage fluctuation of the feedback signal SCS. The driver DRV generates a drive signal SD based on the PWM signal SPWM. Therefore, the power conversion circuit 210 can provide a stable output power supply VOUT based on the voltage fluctuation of the feedback signal SCS.

[0064] When a status signal SSX with a second voltage value (e.g., a preset voltage value higher than the low voltage value) is received, the pulse width modulation signal generator 3211 dynamically determines the duty cycle of the pulse width modulation signal SPWM based on the voltage fluctuations of the feedback signal SCS and the second voltage value of the status signal SSX. At this time, the voltage value of the feedback signal SCS is correlated with the average current value flowing through the power switch SP.

[0065] For example, the duration for which the voltage value of the feedback signal SCS is less than the second voltage value is positively correlated with the duty cycle of the pulse width modulation signal SPWM. Once the voltage value of the feedback signal SCS is less than the second voltage value, it indicates that the power in the boost inductor LB is insufficient. The duty cycle of the pulse width modulation signal SPWM will be increased (this invention is not limited to the adjustment method of this embodiment). Therefore, the on-time of the power switch SP will be increased to allow the boost inductor LB to accumulate sufficient power. Thus, the first controller 321 can accurately adjust the duty cycle of the drive signal SD based on the voltage fluctuations of the feedback signal SCS and the second voltage value of the status signal SSX. In this way, the power conversion circuit 210 can convert the charge stored in the input capacitor CX into a stable output power supply VOUT, thereby consuming the charge stored in the input capacitor CX.

[0066] In some embodiments, the pulse width modulation signal generator 3211 may include a comparator. The comparator provides the pulse width modulation signal SPWM based on a voltage comparison between the voltage value of the feedback signal SCS and the second voltage value of the status signal SSX.

[0067] Please refer to Figure 6 , Figure 6 This is a schematic diagram of a power conversion device according to a fourth embodiment of the present invention. In this embodiment, the power conversion device 400 includes a power conversion circuit 410 and a control circuit 220. The power conversion circuit 410 includes an input capacitor CX, a rectifier circuit RC, a power switch SP, a boost inductor LB, an output diode DO, an output capacitor CO, and a current sensing circuit 411. The input capacitor CX is coupled to the input terminal of the power conversion device 200. The rectifier circuit RC converts the input AC power VAC into rectified power VR. The first terminal of the power switch SP is coupled to the rectifier circuit RC. The boost inductor LB is coupled between the rectifier circuit RC and the first terminal of the power switch SP. The second terminal of the power switch SP is coupled to a reference low voltage. The control terminal of the power switch SP is coupled to the control circuit 220. The anode of the output diode DO is coupled to the first terminal of the power switch SP. The cathode of the output diode DO serves as the output terminal of the power conversion circuit 210. The output capacitor CO is coupled between the cathode of the output diode DO and the reference low voltage.

[0068] The coupling method of the current sensing circuit 411 in this embodiment is similar to... Figure 2The coupling method of the current sensing circuit 211 shown is not the same. In this embodiment, the current sensing circuit 411 is coupled between the low-voltage terminal of the bridge rectifier FBC of the rectifier circuit and a reference low voltage. The current sensing circuit 411 provides a feedback signal SCS in response to the current value flowing through the power switch SP. The current sensing circuit 211 includes a sensing resistor RCS. The first terminal of the sensing resistor RCS is coupled to the low-voltage terminal of the bridge rectifier FBC of the rectifier circuit. The second terminal of the sensing resistor RCS is coupled to the reference low voltage. The second terminal of the sensing resistor RCS is used to provide the feedback signal SCS.

[0069] In this embodiment, the configuration of the control circuit 220 has already been... Figure 2 The embodiments are clearly illustrated, so they will not be repeated here.

[0070] In summary, the power conversion device and control circuit of the present invention utilize a second controller to detect the signal waveform at the input terminal and, in response to the signal waveform at the input terminal, control a first controller to discharge the charge stored in the input capacitor using a power switch. In this way, compared to existing input capacitor discharge functions, the present invention can reduce power consumption and maintain high efficiency and high power factor of the power conversion device. The present invention discharges the charge stored in the input capacitor through existing loops or power conversion functions of the power conversion circuit. Therefore, the design of the power conversion circuit does not need to be changed. Furthermore, the present invention dynamically adjusts the duty cycle of the drive signal through a feedback signal. Thus, based on the duty cycle of the drive signal, the discharge current value or discharge energy used to release the charge stored in the input capacitor is substantially constant.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power conversion device, characterized in that, The power conversion device includes: The power conversion circuit includes: An input capacitor is coupled to the input terminal of the power conversion device; A rectifier circuit, coupled to the input terminal, is configured to convert the input AC power supply into a rectified power supply; and A power switch, wherein a first terminal of the power switch is coupled to the rectifier circuit, and the power conversion circuit provides a feedback signal based on the current value flowing through the power switch; and Control circuit, including: A first controller, coupled to the control terminal of the power switch, is configured to operate the power switch, thereby causing the power conversion circuit to convert the rectified power supply into an output power supply; and A second controller, coupled to the input terminal and the first controller, is configured to detect the signal waveform at the input terminal and control the first controller in response to the signal waveform at the input terminal. The second controller includes a detection circuit and a discharge control circuit. The discharge control circuit is coupled to the detection circuit and the first controller. The discharge control circuit is configured to disable in response to a state signal having a first voltage value and enable in response to a state signal having a second voltage value to control the power switch, thereby discharging the charge stored in the input capacitor. The discharge control circuit includes: An operational amplifier, coupled to the power switch and the detection circuit, is configured to respond to the state signal having the second voltage value being enabled to control the power switch based on a comparison between the feedback signal and the reference signal.

2. The power conversion device according to claim 1, characterized in that, The detection circuit is coupled to the input terminal and is configured to detect the signal waveform at the input terminal, and generate a status signal based on the signal waveform at the input terminal. When the waveform of the input AC power supply is detected, the detection circuit generates the status signal having the first voltage value. When no waveform of the input AC power supply is detected within a preset time period, the detection circuit generates the status signal having the second voltage value, and The preset time length is equal to multiple cycles of the input AC power supply.

3. The power conversion device according to claim 2, characterized in that, The second controller responds to the state signal having the second voltage value to disable the first controller and allows the charge stored in the input capacitor to flow through the first terminal and the second terminal of the power switch.

4. The power conversion device according to claim 1, characterized in that, The power conversion circuit further includes: A current sensing circuit, coupled between the second terminal of the power switch and a reference low voltage, is configured to provide a feedback signal in response to the current value flowing through the power switch.

5. The power conversion device according to claim 1, characterized in that, The power conversion circuit further includes: A current sensing circuit, coupled between the low-voltage end of the bridge rectifier of the rectifier circuit and a reference low voltage, is configured to provide a feedback signal in response to the current value flowing through the power switch.

6. The power conversion device according to claim 2, characterized in that: The second controller detects the signal waveform at the input terminal to determine whether the power conversion circuit receives the input AC power, and When the power conversion circuit does not receive the input AC power, the second controller controls the first controller to cause the power conversion circuit to convert the charge stored in the input capacitor into the output power to consume the charge stored in the input capacitor.

7. The power conversion device according to claim 6, characterized in that, Based on the control of the second controller, the first controller generates a pulse width modulation signal according to the fluctuation of the feedback signal and the second voltage value, generates a drive signal according to the pulse width modulation signal, and provides the drive signal to the control terminal of the power switch.

8. The power conversion device according to claim 7, characterized in that, The duty cycle of the drive signal is related to the voltage value of the feedback signal.

9. The power conversion device according to claim 1, characterized in that, The power conversion circuit further includes: A boost inductor is coupled between the rectifier circuit and the first terminal of the power switch; An output diode, wherein the anode of the output diode is coupled to the first terminal of the power switch, and the cathode of the output diode serves as the output terminal of the power conversion circuit; and An output capacitor is coupled between the cathode of the output diode and a reference low voltage.

10. A control circuit for controlling a power conversion circuit, characterized in that, The power conversion circuit includes an input capacitor, a rectifier circuit, and a power switch. The power conversion circuit provides a feedback signal based on the current value flowing through the power switch. The input capacitor is coupled to the input terminal of the power conversion circuit. The rectifier circuit is configured to convert the input AC power into rectified power. A first terminal of the power switch is coupled to the rectifier circuit. The control circuit includes: A first controller, coupled to the control terminal of the power switch, is configured to operate the power switch, thereby causing the power conversion circuit to convert the rectified power supply into an output power supply; and A second controller, coupled to the input terminal and the first controller, is configured to detect the signal waveform at the input terminal and control the first controller in response to the signal waveform at the input terminal. The second controller includes a detection circuit and a discharge control circuit. The discharge control circuit is coupled to the detection circuit and the first controller. The discharge control circuit is configured to disable in response to a state signal having a first voltage value and enable in response to a state signal having a second voltage value to control the power switch, thereby discharging the charge stored in the input capacitor. The discharge control circuit includes: An operational amplifier, coupled to the power switch and the detection circuit, is configured to respond to the state signal having the second voltage value being enabled to control the power switch based on a comparison between the feedback signal and the reference signal.

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