Withstand voltage value adjusting circuit and switching power supply

Abstract

The utility model provides a withstand voltage value adjusting circuit and a switching power supply. The withstand voltage value adjusting circuit comprises a rectifier module, a voltage detection module and a capacitor module, the input end of the rectifier module is connected with a pre-stage circuit, and the rectifier module is used for rectifying alternating-current voltage output by the pre-stage circuit to obtain direct-current voltage; the voltage detection module is connected with the output end of the rectifier module and is used for receiving the direct current voltage output by the rectifier module; the capacitor circuit comprises a plurality of electrolytic capacitors, one ends of the plurality of electrolytic capacitors are connected with the pre-stage circuit, and the other ends of the plurality of electrolytic capacitors are connected with the voltage detection module; wherein the voltage detection module adjusts the series-parallel connection relation among the plurality of electrolytic capacitors according to the magnitude of the direct current voltage so as to adjust the withstand voltage value of the capacitor module. According to the utility model, the requirement of high withstand voltage value can be met through the electrolytic capacitor with low withstand voltage value, so that the size of the switching power supply can be reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of switching power supplies, in particular to a withstand voltage adjustment circuit and a switching power supply. Background Art

[0002] The capacitance and withstand voltage are two important parameters of capacitors. The capacitance refers to the capacity of the capacitor, and the withstand voltage refers to the maximum DC voltage that the capacitor can withstand in long-term effective work. Generally speaking, the larger the capacitance, the larger the volume, and for capacitors of the same capacitance, the larger the withstand voltage, the larger the volume.

[0003] At present, the size of the electrolytic capacitor in the switching power supply generally increases with the increase of the power of the switching power supply, that is, the greater the output power of the switching power supply, the larger the size of the electrolytic capacitor. However, since most of the current high-power switching power supplies use electrolytic capacitors with high withstand voltage values, the size of the switching power supply is further increased, resulting in higher costs. Utility Model Content

[0004] The utility model provides a withstand voltage adjustment circuit and a switching power supply, aiming to solve the problems of large volume and high cost of the current switching power supply.

[0005] In a first aspect, the utility model provides a withstand voltage adjustment circuit, which includes a rectifier module, a voltage detection module and a capacitor module; the input end of the rectifier module is connected to the front-stage circuit, and is used to rectify the AC voltage output by the front-stage circuit to obtain a DC voltage; the voltage detection module is connected to the output end of the rectifier module, and is used to receive the DC voltage output by the rectifier module; the capacitor module includes a plurality of electrolytic capacitors, one end of each of the electrolytic capacitors is connected to the front-stage circuit, and the other end of each of the electrolytic capacitors is connected to the voltage detection module; wherein the voltage detection module adjusts the series-parallel relationship between the plurality of electrolytic capacitors according to the size of the DC voltage to adjust the withstand voltage of the capacitor module.

[0006] Furthermore, the rectifier module includes a first diode and a second diode; the anode of the first diode and the anode of the second diode are both connected to the front-stage circuit, and the cathode of the first diode and the cathode of the second diode are both connected to the voltage detection module.

[0007] Furthermore, the voltage detection module includes a first switch tube and a second switch tube; the controlled end of the first switch tube, the first pole of the first switch tube and the controlled end of the second switch tube are all connected to the output end of the rectifier module, the first pole of the second switch tube is connected to the capacitor module, and the second pole of the first switch tube and the second pole of the second switch tube are both grounded.

[0008] Furthermore, the voltage detection module also includes a first resistor and a second resistor; one end of the first resistor and one end of the second resistor are both connected to the output end of the rectifier module, the other end of the first resistor is connected to the controlled end of the first switch tube, and the other end of the second resistor is respectively connected to the first pole of the first switch tube and the controlled end of the second switch tube.

[0009] Furthermore, the voltage detection module also includes a third resistor, a first capacitor and a third diode; one end of the third resistor, one end of the first capacitor and the cathode of the third diode are all connected to the first resistor, and the other end of the third resistor, the other end of the first capacitor and the anode of the third diode are all grounded.

[0010] Furthermore, the voltage detection module also includes a fourth resistor, a second capacitor, a fourth diode and a fifth diode; one end of the fourth resistor, one end of the second capacitor and the cathode of the fourth diode are all connected to the second resistor, and the other end of the fourth resistor, the other end of the second capacitor and the other end of the fourth diode are all grounded; the fifth diode is connected in parallel with the second switch tube, and the cathode of the fifth diode is connected to the capacitor module, and the anode of the fifth diode is grounded.

[0011] Furthermore, the capacitor module includes a first capacitor circuit and a second capacitor circuit connected in series; one end of the first capacitor circuit is connected to the previous stage circuit, and the other end of the first capacitor circuit is connected to the first pole of the second switching tube; the first capacitor circuit includes a plurality of electrolytic capacitors connected in parallel, and the second capacitor circuit includes at least one electrolytic capacitor.

[0012] Furthermore, the first capacitor circuit includes a first electrolytic capacitor and a second electrolytic capacitor, the first electrolytic capacitor and the second electrolytic capacitor are connected in parallel, and the first electrolytic capacitor and the second electrolytic capacitor are respectively connected to the previous stage circuit, the first electrode of the first switching tube and the second capacitor circuit.

[0013] Furthermore, the second capacitor circuit includes a third electrolytic capacitor, a sixth diode and a seventh diode; one end of the third electrolytic capacitor is connected to the cathode of the sixth diode and the anode of the seventh diode, the anode of the sixth diode is respectively connected to the first electrolytic capacitor and the second electrolytic capacitor, the cathode of the seventh diode is connected to the previous stage circuit, and the other end of the third electrolytic capacitor is grounded.

[0014] In a second aspect, the utility model further provides a switching power supply, wherein the switching power supply comprises the withstand voltage adjustment circuit described in any one of the above items.

[0015] The switching power supply disclosed by the utility model includes a withstand voltage value adjustment circuit, which includes a rectifier module, a voltage detection module and a capacitor module. The rectifier module rectifies the AC voltage output by the front-stage circuit to obtain a DC voltage. The voltage detection module is connected to the rectifier module and is used to detect the voltage magnitude of the DC voltage. The capacitor module includes a plurality of electrolytic capacitors with the same withstand voltage value, and the plurality of electrolytic capacitors are connected in series or in parallel. The voltage detection module can adjust the series-parallel relationship between the plurality of electrolytic capacitors according to the magnitude of the DC voltage to adjust the withstand voltage value of the capacitor module. When the DC voltage is relatively large, the electrolytic capacitors can be connected in series to increase the withstand voltage value, thereby reducing the demand for the withstand voltage value of a single capacitance value, reducing the volume of the electrolytic capacitor, and further reducing the volume of the switching power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a block diagram of a withstand voltage adjustment circuit provided by an embodiment of the utility model;

[0018] Figure 2 The utility model provides a circuit diagram of a withstand voltage adjustment circuit according to an embodiment of the utility model. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0020] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, operations, elements, components and / or groups thereof.

[0021] It should also be understood that the terms used in this utility model specification are only for the purpose of describing specific embodiments and are not intended to limit the utility model. As used in the utility model specification and the appended claims, the singular forms of "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise. It should also be further understood that the term "and / or" used in the utility model specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0022] In addition, the directional terms mentioned in the present invention, such as "upper", "lower", "front", "back", "left", "right", "inner", "outer", "side", etc., are only for reference to the directions of the attached drawings and the use status of the product. Therefore, the directional terms used are used to illustrate and understand the present invention, but not to limit the present invention. In addition, in the drawings, structures with similar or identical structures are represented by the same reference numerals.

[0023] See also Figure 1 to Figure 2 , Figure 1 1 is a block diagram of a withstand voltage adjustment circuit 100 provided in one embodiment of the utility model; Figure 2 FIG. 1 is a circuit diagram of a withstand voltage adjustment circuit 100 provided in an embodiment of the present invention. Figure 1 As shown, the withstand voltage adjustment circuit 100 includes a rectifier module 10, a voltage detection module 20 and a capacitor module 30; the input end of the rectifier module 10 is connected to the front-stage circuit 200, and is used to rectify the AC voltage output by the front-stage circuit 200 to obtain a DC voltage; the voltage detection module 20 is connected to the output end of the rectifier module 10, and is used to receive the DC voltage output by the rectifier module 10; the capacitor module 30 includes a plurality of electrolytic capacitors, one end of each of the electrolytic capacitors is connected to the front-stage circuit 200, and the other end of each of the electrolytic capacitors is connected to the voltage detection module 20; wherein the voltage detection module 20 adjusts the series-parallel relationship between the plurality of electrolytic capacitors according to the size of the DC voltage to adjust the withstand voltage of the capacitor module 30.

[0024] Specifically, the withstand voltage adjustment circuit 100 includes a rectifier module 10, a voltage detection module 20 and a capacitor module 30. The rectifier module 10 is connected to the front-stage circuit 200, and is used to receive the AC voltage output by the front-stage circuit 200 for rectification and filtering, thereby obtaining a DC voltage, and then outputting the DC voltage to the voltage detection module 20. The front-stage circuit 200 is connected to the rear-stage circuit 300, and is used to provide voltage for the rear-stage circuit 300.

[0025] The voltage detection module 20 is connected to the rectifier module 10, and is used to receive the DC current and adjust the series-parallel relationship of the electrolytic capacitors in the capacitor module 30 according to the DC voltage. The voltage detection module 20 may include multiple switch circuits, and different switch circuits are used to adjust the series-parallel relationship of the electrolytic capacitors in the capacitor module 30.

[0026] The capacitor module 30 includes a plurality of electrolytic capacitors, which can be connected in series or in parallel. For example, two electrolytic capacitors can be connected in series or in parallel under the control of the voltage detection module 20 to provide different withstand voltage values, or three electrolytic capacitors can be included, two of which are connected in parallel, and the parallel circuit formed can be connected in series with another electrolytic capacitor under the control of the voltage detection module 20. The withstand voltage values ​​of the electrolytic capacitors included in the capacitor module 30 are all the same. When the DC voltage is high, the withstand voltage value can be increased by connecting a plurality of electrolytic capacitors in series.

[0027] Taking the low voltage less than 180V and the high voltage greater than 210V as an example, when the DC voltage detected by the voltage detection module 20 is less than 180V, it is a low voltage and a lower capacitance is required. The series-parallel relationship of the electrolytic capacitors in the capacitor module 30 can be controlled to meet the low voltage withstand voltage requirement. When the DC voltage detected by the voltage detection module 20 is greater than 210V, it is a high voltage and a higher withstand voltage is required. The electrolytic capacitors in the capacitor module 30 can be controlled to be connected in series to meet the high voltage withstand voltage requirement.

[0028] As a further embodiment, the rectifier module 10 includes a first diode D1 and a second diode D2; the anode of the first diode D1 and the anode of the second diode D2 are both connected to the front-stage circuit 200, and the cathode of the first diode D1 and the cathode of the second diode D2 are both connected to the voltage detection module 20.

[0029] The first diode D1 and the second diode D2 are used as rectifying diodes to rectify the AC voltage of the front-stage circuit 200 to obtain a DC voltage, and input the DC voltage to the voltage detection module 20 .

[0030] As a further embodiment, the voltage detection module 20 includes a first switch tube Q1 and a second switch tube Q2; the controlled end of the first switch tube Q1, the first pole of the first switch tube Q1 and the controlled end of the second switch tube Q2 are all connected to the output end of the rectifier module 10, the first pole of the second switch tube Q2 is connected to the capacitor module 30, and the second pole of the first switch tube Q1 and the second pole of the second switch tube Q2 are both grounded. Further, the voltage detection module 20 also includes a first resistor R1 and a second resistor R2; one end of the first resistor R1 and one end of the second resistor R2 are both connected to the output end of the rectifier module 10, the other end of the first resistor R1 is connected to the controlled end of the first switch tube Q1, and the other end of the second resistor R2 is respectively connected to the first pole of the first switch tube Q1 and the controlled end of the second switch tube Q2. Further, the voltage detection module 20 also includes a third resistor R3, a first capacitor C1 and a third diode D3; one end of the third resistor R3, one end of the first capacitor C1 and the cathode of the third diode D3 are all connected to the first resistor R1, and the other end of the third resistor R3, the other end of the first capacitor C1 and the anode of the third diode D3 are all grounded. Further, the voltage detection module 20 also includes a fourth resistor R4, a second capacitor C2, a fourth diode D4 and a fifth diode D5; one end of the fourth resistor R4, one end of the second capacitor C2 and the cathode of the fourth diode D4 are all connected to the second resistor R2, and the other end of the fourth resistor R4, the other end of the second capacitor C2 and the other end of the fourth diode D4 are all grounded; the fifth diode D5 is connected in parallel with the second switch tube Q2, and the cathode of the fifth diode D5 is connected to the capacitor module 30, and the anode of the fifth diode D5 is grounded.

[0031] Among them, the controlled ends of the first switch tube Q1 and the second switch tube Q2 are both connected to the output end of the rectifier module 10, and are used to turn on and off according to the magnitude of the DC voltage. That is, the first switch tube Q1 and the second switch tube Q2 are used as devices for detecting the magnitude of the DC voltage. For example, the first switch tube Q1 is set to be turned on at a high voltage, and the second switch tube Q2 is set to be turned on at a low voltage. When the input DC voltage is a low voltage, the first switch tube Q1 is turned off and the second switch tube Q2 is turned on. When the input DC voltage is a high voltage, the first switch tube Q1 is turned on and the second switch tube Q2 is turned off.

[0032] The first switch tube Q1 and the second switch tube Q2 can be triodes or MOS tubes. Taking the case where the first switch tube Q1 and the second switch tube Q2 are both MOS tubes as an example, the gate of the first switch tube Q1 and the gate of the second switch tube Q2 are both connected to the rectifier module 10, the emitter of the first switch tube Q1 and the emitter of the second switch tube Q2 are both grounded, the collector of the first switch tube Q1 is connected to the rectifier module 10, and the collector of the second switch tube Q2 is connected to the capacitor module 30.

[0033] As a further embodiment, the capacitor module 30 includes a first capacitor circuit 31 and a second capacitor circuit 32 connected in series; one end of the first capacitor circuit 31 is connected to the pre-stage circuit 200, and the other end of the first capacitor circuit 31 is connected to the first pole of the second switch tube Q2; the first capacitor circuit 31 includes a plurality of electrolytic capacitors connected in parallel, and the second capacitor circuit 32 includes at least one electrolytic capacitor.

[0034] Among them, the first capacitor circuit 31 and the second capacitor circuit 32 are connected in series, and the first capacitor circuit 31 includes multiple electrolytic capacitors connected in parallel, and the second capacitor circuit 32 includes at least one electrolytic capacitor. When the second capacitor circuit 32 includes multiple electrolytic capacitors, the multiple electrolytic capacitors are connected in series.

[0035] The multiple electrolytic capacitors in the first capacitor circuit 31 are connected in parallel with each other, that is, the withstand voltage value of the first capacitor circuit 31 is the electrolytic capacitor with the lowest withstand voltage value, and the withstand voltage value of each electrolytic capacitor in the first capacitor circuit 31 is the same. When the input voltage is low voltage, the electrolytic capacitors in the first capacitor circuit 31 participate in the circuit operation, and the low withstand voltage value can meet the demand. It can be understood that the number of electrolytic capacitors included in the first capacitor circuit 31 is related to the power of the switching power supply. The greater the power of the switching power supply, the greater the number of electrolytic capacitors included in the first capacitor circuit 31.

[0036] Multiple electrolytic capacitors in the second capacitor circuit 32 are connected in series with each other, and the connectivity between the first capacitor circuit 31 and the second capacitor circuit 32 is controlled by the second switch tube Q2. When the second switch tube Q2 is turned on, the first capacitor circuit 31 and the second capacitor circuit 32 are not connected. When the second switch tube Q2 is turned off, the first capacitor circuit 31 and the second capacitor circuit 32 are connected. At this time, the first capacitor circuit 31 and the second capacitor circuit 32 are connected in series, thereby increasing the withstand voltage value of the entire capacitor module 30 to meet the high voltage requirements.

[0037] Furthermore, the first capacitor circuit 31 includes a first electrolytic capacitor EC1 and a second electrolytic capacitor EC2, the first electrolytic capacitor EC1 and the second electrolytic capacitor EC2 are connected in parallel, and the first electrolytic capacitor EC1 and the second electrolytic capacitor EC2 are respectively connected to the pre-stage circuit 200, the first electrode of the first switch tube Q1 and the second capacitor circuit 32.

[0038] Among them, the first capacitor circuit 31 may include two electrolytic capacitors connected in parallel, namely, a first electrolytic capacitor EC1 and a second electrolytic capacitor EC2, the first electrolytic capacitor EC1 and the second electrolytic capacitor EC2 have the same withstand voltage value, and the capacitance of the two is related to the output power of the switching power supply. When the DC voltage is low, the withstand voltage value of the first electrolytic capacitor EC1 and the second electrolytic capacitor EC2 can meet the demand, and when the DC voltage is high, the first electrolytic capacitor EC1 and the second electrolytic capacitor EC2 are connected in series with the second capacitor C2, so that the withstand voltage value can be increased to meet the high voltage demand.

[0039] Furthermore, the second capacitor circuit 32 includes a third electrolytic capacitor EC3, a sixth diode D6 and a seventh diode D7; one end of the third electrolytic capacitor EC3 is connected to the cathode of the sixth diode D6 and the anode of the seventh diode D7, the anode of the sixth diode D6 is respectively connected to the first electrolytic capacitor EC1 and the second electrolytic capacitor EC2, the cathode of the seventh diode D7 is connected to the pre-stage circuit 200, and the other end of the third electrolytic capacitor EC3 is grounded.

[0040] Among them, the second capacitor circuit 32 may include one third electrolytic capacitor EC3, or may include multiple third electrolytic capacitors EC3. The number of electrolytic capacitors included in the second capacitor circuit 32 is related to the maximum voltage of the DC voltage. The higher the maximum voltage of the DC voltage, the greater the number of electrolytic capacitors in the corresponding second capacitor circuit 32.

[0041] When the second switch tube Q2 is turned off, the first capacitor circuit 31 and the second capacitor circuit 32 are connected in series through the sixth diode D6. At this time, the withstand voltage value of the capacitor module 30 is the sum of the withstand voltage value of any electrolytic capacitor in the first capacitor circuit 31 and the withstand voltage values ​​of all electrolytic capacitors in the second capacitor circuit 32. Due to the characteristics of the sixth diode D6, its conduction angle is small after rectification, and a high-capacitance capacitor is not required for filtering, which further reduces the volume of the electrolytic capacitor.

[0042] Taking the example that the withstand voltage values ​​of the first electrolytic capacitor EC1, the second electrolytic capacitor EC2 and the third electrolytic capacitor EC3 are all 250V, when the second switch tube Q2 is turned on, the withstand voltage value of the capacitor module 30 is 250V, which can meet the low voltage withstand voltage requirement. When the second switch tube Q2 is turned off, the withstand voltage value of the capacitor module 30 is 500V, which can meet the high voltage withstand voltage requirement.

[0043] The utility model also provides a switching power supply, which includes a withstand voltage adjustment circuit 100 according to any one of the above embodiments, and the withstand voltage adjustment circuit 100 includes a rectifier module 10, a voltage detection module 20 and a capacitor module 30; the input end of the rectifier module 10 is connected to the front-stage circuit 200, and is used to rectify the AC voltage output by the front-stage circuit 200 to obtain a DC voltage; the voltage detection module 20 is connected to the output end of the rectifier module 10, and is used to receive the DC voltage output by the rectifier module 10; the capacitor circuit includes a plurality of electrolytic capacitors, one end of each of the electrolytic capacitors is connected to the front-stage circuit 200, and the other end of each of the electrolytic capacitors is connected to the voltage detection module 20; wherein the voltage detection module 20 adjusts the series-parallel relationship between the plurality of electrolytic capacitors according to the size of the DC voltage to adjust the withstand voltage of the capacitor module 30.

[0044] Specifically, the withstand voltage adjustment circuit 100 includes a rectifier module 10, a voltage detection module 20 and a capacitor module 30. The rectifier module 10 is connected to the front-stage circuit 200, and is used to receive the AC voltage output by the front-stage circuit 200 for rectification and filtering, thereby obtaining a DC voltage, and then outputting the DC voltage to the voltage detection module 20. The front-stage circuit 200 is connected to the rear-stage circuit 300, and is used to provide voltage for the rear-stage circuit 300.

[0045] The voltage detection module 20 is connected to the rectifier module 10, and is used to receive the DC current and adjust the series-parallel relationship of the electrolytic capacitors in the capacitor module 30 according to the DC voltage. The voltage detection module 20 may include multiple switch circuits, and different switch circuits are used to adjust the series-parallel relationship of the electrolytic capacitors in the capacitor module 30.

[0046] The capacitor module 30 includes a plurality of electrolytic capacitors, which can be connected in series or in parallel. For example, two electrolytic capacitors can be connected in series or in parallel under the control of the voltage detection module 20 to provide different withstand voltage values, or three electrolytic capacitors can be included, two of which are connected in parallel, and the parallel circuit formed can be connected in series with another electrolytic capacitor under the control of the voltage detection module 20. The withstand voltage values ​​of the electrolytic capacitors included in the capacitor module 30 are all the same. When the DC voltage is high, the withstand voltage value can be increased by connecting a plurality of electrolytic capacitors in series.

[0047] Taking the low voltage less than 180V and the high voltage greater than 210V as an example, when the DC voltage detected by the voltage detection module 20 is less than 180V, it is a low voltage and a lower capacitance is required. The series-parallel relationship of the electrolytic capacitors in the capacitor module 30 can be controlled to meet the low voltage withstand voltage requirement. When the DC voltage detected by the voltage detection module 20 is greater than 210V, it is a high voltage and a higher withstand voltage is required. The electrolytic capacitors in the capacitor module 30 can be controlled to be connected in series to meet the high voltage withstand voltage requirement.

[0048] The voltage-withstand value adjustment circuit disclosed by the utility model adjusts the series-parallel relationship of the electrolytic capacitors in the capacitor module through the voltage detection module, and meets the high voltage-withstand requirement through the low voltage-withstand electrolytic capacitors, thereby reducing the volume of the electrolytic capacitors, and further reducing the volume of the switching power supply.

[0049] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the utility model, and these modifications or replacements should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims.

Claims

1. A withstand voltage adjustment circuit, characterized in that: include: A rectifier module, the input end of which is connected to the front-stage circuit and is used to rectify the AC voltage output by the front-stage circuit to obtain a DC voltage; A voltage detection module, the voltage detection module is connected to the output end of the rectifier module and is used to receive the DC voltage output by the rectifier module; A capacitor module, wherein the capacitor module includes a plurality of electrolytic capacitors, one end of each of the electrolytic capacitors is connected to the front-stage circuit, and the other end of each of the electrolytic capacitors is connected to the voltage detection module; The voltage detection module adjusts the series-parallel relationship between the plurality of electrolytic capacitors according to the magnitude of the DC voltage to adjust the withstand voltage value of the capacitor module.

2. The withstand voltage adjustment circuit according to claim 1, wherein: The rectifier module includes a first diode and a second diode; The anode of the first diode and the anode of the second diode are both connected to the front-stage circuit, and the cathode of the first diode and the cathode of the second diode are both connected to the voltage detection module.

3. The withstand voltage adjustment circuit according to claim 1, wherein: The voltage detection module includes a first switch tube and a second switch tube; The controlled end of the first switch tube, the first electrode of the first switch tube and the controlled end of the second switch tube are all connected to the output end of the rectifier module, the first electrode of the second switch tube is connected to the capacitor module, and the second electrode of the first switch tube and the second electrode of the second switch tube are both grounded.

4. The withstand voltage adjustment circuit according to claim 3, wherein: The voltage detection module also includes a first resistor and a second resistor; One end of the first resistor and one end of the second resistor are both connected to the output end of the rectifier module, the other end of the first resistor is connected to the controlled end of the first switch tube, and the other end of the second resistor is respectively connected to the first electrode of the first switch tube and the controlled end of the second switch tube.

5. The withstand voltage adjustment circuit according to claim 4, wherein: The voltage detection module also includes a third resistor, a first capacitor and a third diode; One end of the third resistor, one end of the first capacitor and a cathode of the third diode are all connected to the first resistor, and the other end of the third resistor, the other end of the first capacitor and anode of the third diode are all grounded.

6. The withstand voltage adjustment circuit according to claim 5, wherein: The voltage detection module also includes a fourth resistor, a second capacitor, a fourth diode and a fifth diode; One end of the fourth resistor, one end of the second capacitor and the cathode of the fourth diode are all connected to the second resistor, and the other end of the fourth resistor, the other end of the second capacitor and the other end of the fourth diode are all grounded; The fifth diode is connected in parallel with the second switch tube, a cathode of the fifth diode is connected to the capacitor module, and an anode of the fifth diode is grounded.

7. The withstand voltage adjustment circuit according to claim 3, wherein: The capacitor module includes a first capacitor circuit and a second capacitor circuit connected in series; One end of the first capacitor circuit is connected to the previous stage circuit, and the other end of the first capacitor circuit is connected to the first electrode of the second switch tube; The first capacitor circuit includes a plurality of electrolytic capacitors connected in parallel, and the second capacitor circuit includes at least one electrolytic capacitor.

8. The withstand voltage adjustment circuit according to claim 7, wherein: The first capacitor circuit includes a first electrolytic capacitor and a second electrolytic capacitor, the first electrolytic capacitor and the second electrolytic capacitor are connected in parallel, and the first electrolytic capacitor and the second electrolytic capacitor are respectively connected to the previous stage circuit, the first electrode of the first switch tube and the second capacitor circuit.

9. The withstand voltage adjustment circuit according to claim 8, wherein: The second capacitor circuit includes a third electrolytic capacitor, a sixth diode and a seventh diode; One end of the third electrolytic capacitor is connected to the cathode of the sixth diode and the anode of the seventh diode, the anode of the sixth diode is connected to the first electrolytic capacitor and the second electrolytic capacitor respectively, the cathode of the seventh diode is connected to the previous stage circuit, and the other end of the third electrolytic capacitor is grounded.

10. A switching power supply, characterized in that: It comprises the withstand voltage adjustment circuit as described in any one of claims 1 to 9.

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