Lightning stroke protection circuit, power supply circuit and charger

Abstract

The utility model discloses a lightning stroke protection circuit, a power supply circuit and a charger. The lightning stroke protection circuit is used for protecting a protected element and comprises a detection circuit, a first protection module and a second protection module, the input end of the detection circuit is connected with a signal input end, the output end of the detection circuit is connected with the first protection module and the second protection module, and the detection circuit is used for outputting protection signals to the first protection module and the second protection module when surge current is generated by lightning stroke; and the first protection module is connected with a connection node between a signal input end and a protected element, and is used for being switched on under the control of the protection signal to absorb surge current. According to the lightning stroke protection circuit, when lightning stroke occurs, the first protection module can absorb lightning stroke energy, the second protection module enables the protected element to be in an open circuit state, dual protection is formed for the protected element, and the lightning stroke resistance of the circuit is enhanced.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply circuits, and in particular to a lightning protection circuit, a power supply circuit and a charger. Background Art

[0002] Lightning is often accompanied by transient high voltage and high current, which can easily affect electronic equipment such as power circuits. Some electronic components in power circuits, such as filter capacitors, are usually unable to withstand the impact of such transient high voltage and are easily damaged by lightning.

[0003] In existing power supply circuits, varistors are used to prevent the impact of lightning strikes. However, the dynamic resistance of varistors is relatively large, and the leakage current is high at low voltages, which can easily cause losses to the circuit. Utility Model Content

[0004] The embodiments of the utility model provide a lightning protection circuit, a power supply circuit and a charger to solve the problem that the high voltage and high current caused by lightning strikes can easily damage the electronic components in the power supply circuit.

[0005] The utility model embodiment provides a lightning protection circuit for protecting a protected element, wherein a first end of the protected element is connected to a signal input end, and a second end of the protected element is grounded, and comprises a detection circuit, a first protection module and a second protection module;

[0006] The input end of the detection circuit is connected to the signal input end, and the output end of the detection circuit is connected to the first protection module and the second protection module, and is used to output a protection signal to the first protection module and the second protection module when a surge current is generated by a lightning strike;

[0007] The first protection module is connected to the connection node between the signal input terminal and the protected element, and is used to be turned on under the control of the protection signal to absorb the surge current;

[0008] The second protection module is connected to the second end of the protected element and is used to be turned off under the control of the protection signal to put the protected element in an open circuit state.

[0009] Preferably, the detection circuit comprises an operational amplifier, a sampling unit and a reference voltage generating unit;

[0010] The first end of the sampling unit is connected to the signal input end, and the second end of the sampling unit is connected to the in-phase input end of the operational amplifier, for outputting a sampling voltage to the operational amplifier;

[0011] The first end of the reference voltage generating unit is connected to the signal input end, and the second end of the reference voltage generating unit is connected to the inverting input end of the operational amplifier, for outputting a reference voltage to the operational amplifier;

[0012] The output end of the operational amplifier is connected to the first protection module and the second protection module, and is used to output a protection signal to the first protection module and the second protection module when the sampling voltage is greater than the reference voltage.

[0013] Preferably, the sampling unit comprises a first resistor and a second resistor;

[0014] The first resistor and the second resistor are connected in series between the signal input terminal and the ground;

[0015] The non-inverting input terminal of the operational amplifier is connected to a connection node between the first resistor and the second resistor.

[0016] Preferably, the reference voltage generating unit comprises a third resistor and a voltage regulator tube;

[0017] The first end of the third resistor is connected to the signal input end, the second end of the third resistor is connected to the first end of the voltage regulator tube, and the second end of the voltage regulator tube is grounded;

[0018] The inverting input terminal of the operational amplifier is connected to a connection node between the voltage regulator tube and the third resistor.

[0019] Preferably, the first protection module includes a first capacitor, a first switch tube and a fourth resistor;

[0020] The first end of the first capacitor is connected to the first end of the protected element, and the second end of the first capacitor is connected to the first end of the first switch tube;

[0021] The second end of the first switch tube is connected to the output end of the detection circuit, and the third end of the first switch tube is grounded, and is used to be turned on under the control of the protection signal, so that the first capacitor can absorb the surge current;

[0022] The fourth resistor is connected in parallel to both ends of the first capacitor, and is used to discharge the surge current absorbed by the first capacitor.

[0023] Preferably, the first protection module further comprises a transient suppression diode;

[0024] The transient voltage suppression diode is connected in parallel with the first capacitor.

[0025] Preferably, the first protection module further includes a first diode;

[0026] The anode of the first diode is connected to the output end of the detection circuit, and the cathode of the first diode is connected to the second end of the first switch tube.

[0027] Preferably, the first protection module further includes a fifth resistor;

[0028] A first end of the fifth resistor is connected to a connection node between the first diode and the first switch tube, and a second end of the fifth resistor is grounded.

[0029] Preferably, the second protection module includes a second switch tube;

[0030] The first end of the second switch tube is connected to the second end of the protected element, the second end of the second switch tube is connected to the output end of the detection circuit, and the third end of the second switch tube is grounded, and is used to shut down under the control of the protection signal to put the protected element in an open circuit state.

[0031] The embodiment of the utility model further provides a power supply circuit, comprising a rectifier circuit, a filter capacitor and any one of the above-mentioned lightning protection circuits;

[0032] The input end of the rectifier circuit is used to connect to the mains circuit, and the output end of the rectifier circuit is the signal input end of the lightning protection circuit;

[0033] The filter capacitor is the protected element, a first end of the filter capacitor is connected to the output end of the rectifier circuit, and a second end of the filter capacitor is grounded.

[0034] An embodiment of the utility model further provides a charger, comprising the above-mentioned power supply circuit.

[0035] The lightning protection circuit, power supply circuit and charger provided by the embodiments of the utility model, by setting the lightning protection circuit in the power supply circuit, can absorb the lightning energy through the first protection module when lightning strikes, and put the protected element in an open circuit state through the second protection module to prevent the lightning energy from flowing into the protected element, thereby forming double protection for the protected element and enhancing the circuit's ability to resist lightning strikes. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] 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 of the utility model will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 It is a circuit structure diagram of a power supply circuit in one embodiment of the utility model.

[0038] In the figure: 1. detection circuit; 11. sampling unit; 12. reference voltage generating unit; 2. first protection module; 3. second protection module; 4. rectification circuit. DETAILED DESCRIPTION

[0039] 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.

[0040] It should be understood that the utility model can be implemented in different forms and should not be construed as being limited to the embodiments presented herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and fully convey the scope of the utility model to those skilled in the art. In the accompanying drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. The same reference numerals throughout represent the same elements.

[0041] It should be understood that when an element or layer is referred to as being "on, adjacent to, connected to or coupled to other elements or layers, it may be directly on, adjacent to, connected to or coupled to other elements or layers, or there may be intervening elements or layers. On the contrary, when an element is referred to as being "directly on, directly adjacent to, directly connected to or directly coupled to other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below may be represented as a second element, component, region, layer or part.

[0042] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," and the like may be used herein for ease of description to describe the relationship of an element or feature shown in the figures to other elements or features. It should be understood that the spatially relative terms are intended to include different orientations of the device in use and operation in addition to the orientations shown in the figures. For example, if the device in the accompanying drawings is flipped, then the elements or features described as "under other elements" or "under" or "under" will be oriented as "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0043] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising" when used in this specification determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0044] In order to thoroughly understand the present invention, detailed structures and steps will be presented in the following description to illustrate the technical solution proposed by the present invention. The preferred embodiments of the present invention are described in detail below, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0045] The embodiment of the utility model provides a lightning protection circuit for protecting a protected element, wherein the first end of the protected element is connected to the signal input end, and the second end of the protected element is grounded. The lightning protection circuit comprises a detection circuit 1, a first protection module 2 and a second protection module 3; the input end of the detection circuit 1 is connected to the signal input end, and the output end of the detection circuit 1 is connected to the first protection module 2 and the second protection module 3, and is used to output a protection signal to the first protection module 2 and the second protection module 3 when a surge current is generated by a lightning strike; the first protection module 2 is connected to a connection node between the signal input end and the protected element, and is used to be turned on under the control of the protection signal to absorb the surge current; the second protection module 3 is connected to the second end of the protected element, and is used to be turned off under the control of the protection signal to put the protected element in an open circuit state.

[0046] As an example, the lightning protection circuit is used to protect a protected element, such as a filter capacitor C2 in a power supply circuit, from lightning strikes. The first end of the protected element is connected to the signal input end, and the second end of the protected element is grounded. The lightning protection circuit includes a detection circuit 1, a first protection module 2 and a second protection module 3. The input end of the detection circuit 1 and the protected element are connected to the same signal input end, the output end of the detection circuit 1 is connected to the first protection module 2 and the second protection module 3, the first protection module 2 is connected to the first end of the protected element, and the second protection module 3 is connected to the second end of the protected element.

[0047] When a lightning strike occurs, a surge current generated by the lightning strike flows in from the signal input terminal. After the detection circuit 1 detects the surge current, it outputs a protection signal to the first protection module 2 and the second protection module 3, so that the first protection module 2 is turned on under the action of the protection signal to absorb the surge current flowing into the signal input terminal, withstand the instantaneous high voltage, absorb the lightning energy, and the second protection module 3 is turned off under the action of the protection signal, so that the second end of the protected element is disconnected from the ground and is in an open circuit state, so that the lightning energy cannot enter the protected element, thereby protecting the protected element.

[0048] In this example, by setting up a lightning protection circuit, when a lightning strike occurs, the lightning energy can be absorbed by the first protection module 2, and the protected element can be placed in an open circuit state through the second protection module 3 to prevent the lightning energy from flowing into the protected element, thereby forming double protection for the protected element and enhancing the circuit's ability to resist lightning strikes.

[0049] In one embodiment, the detection circuit 1 includes an operational amplifier U1, a sampling unit 11 and a reference voltage generating unit 12; the first end of the sampling unit 11 is connected to the signal input end, and the second end of the sampling unit 11 is connected to the non-inverting input end of the operational amplifier U1, for outputting a sampling voltage to the operational amplifier U1; the first end of the reference voltage generating unit 12 is connected to the signal input end, and the second end of the reference voltage generating unit 12 is connected to the inverting input end of the operational amplifier U1, for outputting a reference voltage to the operational amplifier U1; the output end of the operational amplifier U1 is connected to the first protection module 2 and the second protection module 3, for outputting a protection signal to the first protection module 2 and the second protection module 3 when the sampling voltage is greater than the reference voltage.

[0050] As an example, the detection circuit 1 includes an operational amplifier U1, a sampling unit 11 and a reference voltage generating unit 12. The first end of the sampling unit 11 is connected to the signal input end, and the second end of the sampling unit 11 is connected to the non-inverting input end of the operational amplifier U1. The first end of the reference voltage generating unit 12 is connected to the signal input end, and the second end of the reference voltage generating unit 12 is connected to the inverting input end of the operational amplifier U1. The output end of the operational amplifier U1 is connected to the first protection module 2 and the second protection module 3.

[0051] During the operation of the circuit, the sampling unit 11 collects the current input from the signal input terminal and forms a sampling voltage, which is input to the in-phase input terminal of the operational amplifier U1. The reference voltage generating unit 12 generates a reference voltage according to the voltage input from the signal input terminal and inputs it to the inverting input terminal of the operational amplifier U1. If there is no lightning strike, the reference voltage is greater than or equal to the sampling voltage, and there is no high-level signal output from the output terminal of the operational amplifier U1. When a lightning strike occurs, due to the generation of surge current, the sampling voltage will suddenly increase and be greater than the current reference voltage. At this time, the operational amplifier U1 outputs a protection signal, that is, a high-level signal, so that the first protection module 2 absorbs the surge current flowing into the signal input terminal, withstands the instantaneous high voltage, absorbs the lightning energy, and the second protection module 3 is turned off under the action of the protection signal, so that the second end of the protected element is disconnected from the ground and is in an open circuit state, so that the lightning energy cannot enter the protected element, and the protected element is protected.

[0052] In one embodiment, the sampling unit 11 includes a first resistor R1 and a second resistor R2; the first resistor R1 and the second resistor R2 are connected in series between the signal input terminal and the ground; the non-inverting input terminal of the operational amplifier U1 is connected to the connection node between the first resistor R1 and the second resistor R2.

[0053] As an example, the sampling unit 11 includes a first resistor R1 and a second resistor R2, wherein the first end of the first resistor R1 is connected to the signal input end, the second end of the first resistor R1 is connected to the first end of the second resistor R2, the second end of the second resistor R2 is grounded, and the in-phase input end of the operational amplifier U1 is connected to the first end of the second resistor R2. The first resistor R1 and the second resistor R2 form a current limiting and voltage dividing effect on the voltage input to the sampling unit 11, so that the voltage input to the in-phase input end of the operational amplifier U1, that is, the sampling voltage, is the same as the voltage across the second resistor R2.

[0054] In one embodiment, the reference voltage generating unit 12 includes a third resistor R3 and a voltage regulator D1; the first end of the third resistor R3 is connected to the signal input end, the second end of the third resistor R3 is connected to the first end of the voltage regulator D1, and the second end of the voltage regulator D1 is grounded; the inverting input end of the operational amplifier U1 is connected to the connection node between the voltage regulator D1 and the third resistor R3, and is used to input a reference voltage to the operational amplifier U1.

[0055] As an example, the reference voltage generating unit 12 includes a third resistor R3 and a voltage regulator D1, wherein the first end of the third resistor R3 is connected to the signal input end, the second end of the third resistor R3 is connected to the first end of the voltage regulator D1, the second end of the voltage regulator D1 is grounded, and the inverting input end of the operational amplifier U1 is connected to the connection node between the voltage regulator D1 and the third resistor R3. The third resistor R3 forms a voltage divider for the voltage input to the voltage regulator D1, and the voltage across the voltage regulator D1 does not change with the voltage at the signal input end, so a fixed reference voltage can be formed at the inverting input end of the operational amplifier U1.

[0056] In one embodiment, the first protection module 2 includes a first capacitor C1, a first switch tube Q1 and a fourth resistor R4; the first end of the first capacitor C1 is connected to the first end of the protected element, and the second end of the first capacitor C1 is connected to the first end of the first switch tube Q1; the second end of the first switch tube Q1 is connected to the output end of the detection circuit 1, and the third end of the first switch tube Q1 is grounded, and is used to be turned on under the control of the protection signal, so that the first capacitor C1 can absorb the surge current; the fourth resistor R4 is connected in parallel to the two ends of the first capacitor C1, and is used to discharge the surge current absorbed by the first capacitor C1.

[0057] As an example, the first protection module 2 includes a first capacitor C1, a first switch tube Q1 and a fourth resistor R4. Among them, the first capacitor C1 can be an electrolytic capacitor with high voltage resistance, the first switch tube Q1 can be an NMOS tube, the first end of the first switch tube Q1 is the drain of the NMOS tube, the second end of the first switch tube Q1 is the gate of the NMOS tube, and the third end of the first switch tube Q1 is the source of the NMOS tube. The first end of the first capacitor C1 is connected to the same signal input end as the protected element, the second end of the first capacitor C1 is connected to the drain of the NMOS tube, the gate of the NMOS tube is connected to the output end of the detection circuit 1, and the source of the NMOS tube is grounded. The fourth resistor R4 is connected in parallel to both ends of the first capacitor C1.

[0058] During the operation of the circuit, if there is no lightning strike, the detection circuit 1 does not operate, the gate of the NMOS tube is in a low level state, the NMOS tube is turned off, and the first capacitor C1 in the first protection module 2 cannot absorb the current from the signal input end. When a lightning strike occurs, the detection circuit 1 outputs a protection signal to the NMOS tube, that is, outputs a high level signal. At this time, the NMOS tube is turned on, and the first capacitor C1 in the first protection module 2 absorbs the surge current flowing into the signal input end, and withstands the instantaneous high voltage to absorb the lightning energy. After the lightning strike ends, the detection circuit 1 continues to maintain a low level output, the NMOS tube is turned off, and the lightning energy absorbed by the first capacitor C1 is discharged through the fourth resistor R4, preparing for the next time the first capacitor C1 absorbs the lightning energy.

[0059] In one embodiment, the first protection module 2 further includes a transient suppression diode ZV1 ; the transient suppression diode ZV1 is connected in parallel with the first capacitor C1 .

[0060] As an example, the first protection module 2 also includes a transient suppression diode ZV1, which is connected in parallel at both ends of the first capacitor C1, and is used to clamp the voltage across the first capacitor C1 to an acceptable range of the first capacitor C1 when lightning strikes, the NMOS tube is turned on, and the voltage of the lightning strike is greater than the withstand voltage of the first capacitor C1, so as to protect the first capacitor C1. When the lightning strike voltage is within the withstand voltage range of the first capacitor C1, the transient suppression diode ZV1 has a very high impedance and basically consumes no energy.

[0061] In one embodiment, the first protection module 2 further includes a first diode D2; an anode of the first diode D2 is connected to the output end of the detection circuit 1, and a cathode of the first diode D2 is connected to the second end of the first switch tube Q1.

[0062] As an example, the first protection module 2 also includes a first diode D2, the anode of the first diode D2 is connected to the output end of the detection circuit 1, and the cathode of the first diode D2 is connected to the gate of the NMOS tube, which is used to isolate the first protection module 2 from the second protection module 3 to prevent the voltage of the second protection module 3 from being connected to the first protection module 2 and causing misconduction.

[0063] In one embodiment, the first protection module 2 further includes a fifth resistor R5; a first end of the fifth resistor R5 is connected to a connection node between the first diode D2 and the first switch tube Q1, and a second end of the fifth resistor R5 is grounded.

[0064] As an example, the first protection module 2 also includes a fifth resistor R5, a first end of the fifth resistor R5 is connected to the gate of the NMOS tube, and a second end of the fifth resistor R5 is grounded, and is used to discharge the gate voltage of the NMOS tube after the protection signal output by the detection circuit 1, that is, the high-level signal disappears, so that the NMOS tube can be shut down in time after the protection signal disappears to prevent affecting the circuit efficiency.

[0065] In one embodiment, the second protection module 3 includes a second switch tube Q2; the first end of the second switch tube Q2 is connected to the second end of the protected element, the second end of the second switch tube Q2 is connected to the output end of the detection circuit 1, and the third end of the second switch tube Q2 is grounded, and is used to shut down under the control of the protection signal to put the protected element in an open circuit state.

[0066] As an example, the second protection module 3 includes a second switch tube Q2. The second switch tube Q2 may be a PMOS tube, the first end of the second switch tube Q2 is the source of the PMOS tube, the second end of the second switch tube Q2 is the gate of the PMOS tube, and the third end of the second switch tube Q2 is the drain of the PMOS tube. The source of the PMOS tube is connected to the second end of the protected element, the gate of the PMOS tube is connected to the output end of the detection circuit 1, and the drain of the PMOS tube is grounded.

[0067] During the operation of the circuit, if there is no lightning strike, the detection circuit 1 will not operate, the gate of the PMOS tube will be in a low level state, the PMOS tube will be turned on, and the protected components, such as the filter capacitor C2, can work normally. When a lightning strike occurs, the detection circuit 1 outputs a protection signal to the PMOS tube, that is, outputs a high level signal. At this time, the PMOS tube is turned off, so that the second end of the protected component is disconnected from the ground and is in an open circuit state, so that the lightning strike energy cannot enter the protected component, thus protecting the protected component. After the lightning strike ends, the detection circuit 1 continues to maintain a low level output, the PMOS tube is turned on, and the protected component continues to work.

[0068] The embodiment of the utility model also provides a power supply circuit, including a rectifier circuit 4, a filter capacitor C2 and the lightning protection circuit in the above embodiment; the input end of the rectifier circuit 4 is used to connect to the mains circuit, and the output end of the rectifier circuit 4 is the signal input end of the lightning protection circuit; the filter capacitor C2 is a protected element, the first end of the filter capacitor C2 is connected to the output end of the rectifier circuit 4, and the second end of the filter capacitor C2 is grounded.

[0069] As an example, the power supply circuit includes a rectifier circuit 4, a filter capacitor C2 and the lightning protection circuit in the above example. The input end of the rectifier circuit 4 is used to be connected to the mains circuit, the output end of the rectifier circuit 4 is the signal input end of the lightning protection circuit, and the filter capacitor C2 is the protected element. The detection circuit 1 in the lightning protection circuit is connected to the output end of the rectifier circuit 4, the first protection module 2 in the lightning protection circuit is connected to the connection node between the rectifier circuit 4 and the filter capacitor C2, and the second protection module 3 in the lightning protection circuit is connected to the second end of the filter capacitor C2.

[0070] When a lightning strike occurs, the surge current generated by the lightning strike flows in from the signal input end. After the detection circuit 1 detects the surge current, it outputs a protection signal to the first protection module 2 and the second protection module 3, so that the first protection module 2 is turned on under the action of the protection signal to absorb the surge current flowing in from the signal input end, withstand the instantaneous high voltage, absorb the lightning strike energy, and the second protection module 3 is turned off under the action of the protection signal, so that the second end of the filter capacitor C2 is disconnected from the ground and is in an open circuit state, so that the lightning strike energy cannot enter the filter capacitor C2, and the filter capacitor C2 is protected. When the lightning strike disappears, the detection circuit 1 stops outputting the protection signal, the first protection module 2 is turned off, and the second protection module 3 continues to be turned on, so that the second end of the filter capacitor C2 is restored to be connected to the ground, and the circuit is filtered normally again.

[0071] In this example, by setting up a lightning protection circuit, when a lightning strike occurs, the lightning energy can be absorbed by the first protection module 2, and the protected element can be placed in an open circuit state by the second protection module 3, thereby preventing the lightning energy from flowing into the filter capacitor C2, thereby forming a double protection for the filter capacitor C2 and enhancing the circuit's ability to resist lightning strikes.

[0072] An embodiment of the utility model further provides a charger, comprising the power supply circuit in the above embodiment.

[0073] As an example, the charger includes the power supply circuit in the above example. By setting a lightning protection circuit in the power supply circuit, when a lightning strike occurs, the lightning energy can be absorbed by the first protection module 2, and the protected element can be put in an open circuit state through the second protection module 3 to prevent the lightning energy from flowing into the filter capacitor C2, thereby forming double protection for the filter capacitor C2 and enhancing the circuit's ability to resist lightning strikes.

[0074] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A lightning protection circuit for protecting a protected element, wherein a first end of the protected element is connected to a signal input end, and a second end of the protected element is grounded, wherein: It includes a detection circuit, a first protection module and a second protection module; The input end of the detection circuit is connected to the signal input end, and the output end of the detection circuit is connected to the first protection module and the second protection module, and is used to output a protection signal to the first protection module and the second protection module when a surge current is generated by a lightning strike; The first protection module is connected to the connection node between the signal input terminal and the protected element, and is used to be turned on under the control of the protection signal to absorb the surge current; The second protection module is connected to the second end of the protected element and is used to be turned off under the control of the protection signal to put the protected element in an open circuit state.

2. The lightning protection circuit according to claim 1, characterized in that: The detection circuit includes an operational amplifier, a sampling unit and a reference voltage generating unit; The first end of the sampling unit is connected to the signal input end, and the second end of the sampling unit is connected to the in-phase input end of the operational amplifier, for outputting a sampling voltage to the operational amplifier; The first end of the reference voltage generating unit is connected to the signal input end, and the second end of the reference voltage generating unit is connected to the inverting input end of the operational amplifier, for outputting a reference voltage to the operational amplifier; The output end of the operational amplifier is connected to the first protection module and the second protection module, and is used to output a protection signal to the first protection module and the second protection module when the sampling voltage is greater than the reference voltage.

3. The lightning protection circuit according to claim 2, characterized in that: The sampling unit includes a first resistor and a second resistor; The first resistor and the second resistor are connected in series between the signal input terminal and the ground; The non-inverting input terminal of the operational amplifier is connected to a connection node between the first resistor and the second resistor.

4. The lightning protection circuit according to claim 2, characterized in that: The reference voltage generating unit includes a third resistor and a voltage regulator tube; The first end of the third resistor is connected to the signal input end, the second end of the third resistor is connected to the first end of the voltage regulator tube, and the second end of the voltage regulator tube is grounded; The inverting input terminal of the operational amplifier is connected to a connection node between the voltage regulator tube and the third resistor.

5. The lightning protection circuit according to claim 1, characterized in that: The first protection module includes a first capacitor, a first switch tube and a fourth resistor; The first end of the first capacitor is connected to the first end of the protected element, and the second end of the first capacitor is connected to the first end of the first switch tube; The second end of the first switch tube is connected to the output end of the detection circuit, and the third end of the first switch tube is grounded, and is used to be turned on under the control of the protection signal, so that the first capacitor can absorb the surge current; The fourth resistor is connected in parallel to both ends of the first capacitor, and is used to discharge the surge current absorbed by the first capacitor.

6. The lightning protection circuit according to claim 5, characterized in that: The first protection module also includes a transient suppression diode; The transient voltage suppression diode is connected in parallel with the first capacitor.

7. The lightning protection circuit according to claim 5, characterized in that: The first protection module also includes a first diode; The anode of the first diode is connected to the output end of the detection circuit, and the cathode of the first diode is connected to the second end of the first switch tube.

8. The lightning protection circuit according to claim 7, characterized in that: The first protection module also includes a fifth resistor; A first end of the fifth resistor is connected to a connection node between the first diode and the first switch tube, and a second end of the fifth resistor is grounded.

9. The lightning protection circuit according to claim 1, characterized in that: The second protection module includes a second switch tube; The first end of the second switch tube is connected to the second end of the protected element, the second end of the second switch tube is connected to the output end of the detection circuit, and the third end of the second switch tube is grounded, and is used to shut down under the control of the protection signal to put the protected element in an open circuit state.

10. A power supply circuit, characterized in that: It comprises a rectifier circuit, a filter capacitor and a lightning protection circuit according to any one of claims 1 to 9; The input end of the rectifier circuit is used to connect to the mains circuit, and the output end of the rectifier circuit is the signal input end of the lightning protection circuit; The filter capacitor is the protected element, a first end of the filter capacitor is connected to the output end of the rectifier circuit, and a second end of the filter capacitor is grounded.

11. A charger, characterized in that: The invention comprises the power supply circuit as claimed in claim 10.

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