Overvoltage protection circuit

Abstract

The utility model provides an overvoltage protection circuit. The circuit comprises a voltage stabilizing tube circuit, a triode sub-circuit and a field effect tube circuit. The first input end of the field effect transistor circuit, the input end of the voltage stabilizing transistor circuit and the first input end of the triode sub-circuit are respectively connected with the output end of the power supply; the output end of the field effect transistor circuit is connected with the input end of the electronic equipment; the first output end of the voltage stabilizing tube sub-circuit is connected with the second input end of the triode sub-circuit; the output end of the triode sub-circuit is connected with the second input end of the field effect transistor circuit; the second output end of the voltage stabilizing tube circuit is connected with the ground. Through cooperation of the circuits, the power supply and the electronic equipment can be conducted when the power supply voltage is smaller than the preset voltage, and the power supply and the electronic equipment can be cut off when the power supply voltage is larger than or equal to the preset voltage; meanwhile, selected electronic devices are low in cost, easy to obtain and convenient to process, so that the production cost of the whole circuit is low.

Description

Technical Field

[0001] The present application relates to the field of circuit protection technology, and in particular to an overvoltage protection circuit. Background Art

[0002] With the widespread adoption of electronic devices, the power requirements of various electronic products are becoming increasingly diverse. A wide variety of power adapters are available on the market, including common voltage specifications such as 5V, 12V, and 24V. However, users often encounter the problem of incorrectly plugging in power adapters during daily use, causing damage to the device. This is especially true for terminal products such as set-top boxes and routers. Using an incompatible power adapter can cause the motherboard to burn out.

[0003] In order to prevent equipment damage caused by overvoltage, overvoltage protection circuits came into being. Figure 1 The overvoltage protection circuit is connected between the power supply and the system power supply of the electronic device. Its main function is to detect the device's supply voltage and, if an overvoltage exceeds the device's rated range, quickly take protective measures to prevent damage. Currently, the overvoltage protection circuits widely used in the market mainly rely on traditional integrated circuit (IC) designs. However, these solutions are expensive to produce and cannot meet the voltage protection needs of some cost-sensitive consumer electronics products. Utility Model Content

[0004] In view of the above-mentioned problems, the present application is proposed to provide an overvoltage protection circuit that overcomes the problems or at least partially solves the problems, including:

[0005] An overvoltage protection circuit includes a voltage regulator circuit, a triode circuit, a field effect tube circuit and a grounding resistor;

[0006] The first input end of the field effect tube circuit, the input end of the voltage regulator tube circuit, and the first input end of the triode circuit are respectively connected to the output end of the power supply; the output end of the field effect tube circuit is connected to the input end of the electronic device; the first output end of the voltage regulator tube circuit is connected to the second input end of the triode circuit; the output end of the triode circuit is connected to the second input end of the field effect tube circuit; the second output end of the voltage regulator tube circuit is connected to ground; the output end of the triode circuit and the second input end of the field effect tube circuit are respectively connected to one end of the grounding resistor, and the other end of the grounding resistor is connected to ground;

[0007] When the output voltage of the power supply is lower than the preset voltage, the first output terminal of the voltage regulator circuit outputs a high level, the first input terminal and the output terminal of the triode circuit are cut off, and the first input terminal and the output terminal of the field effect tube circuit are connected;

[0008] When the output voltage of the power supply is greater than or equal to the preset voltage, the first output end of the voltage regulator circuit outputs a low level, the first input end and the output end of the transistor circuit are connected, and the first input end and the output end of the field effect tube circuit are cut off.

[0009] Preferably, the voltage-stabilizing tube circuit includes a voltage-stabilizing tube and a current-limiting resistor;

[0010] The cathode of the voltage-stabilizing diode and one end of the current-limiting resistor are respectively connected to the output end of the power supply, the anode of the voltage-stabilizing diode is connected to the ground, and the other end of the current-limiting resistor is connected to the second input end of the triode sub-circuit;

[0011] When the output voltage of the power supply is lower than the preset voltage, the voltage regulator is turned off, and the end of the current limiting resistor connected to the transistor subcircuit outputs a high level;

[0012] When the output voltage of the power supply is greater than or equal to the preset voltage, the voltage regulator is turned on, and the end of the current limiting resistor connected to the transistor subcircuit outputs a low level.

[0013] Preferably, the voltage regulator circuit further includes a first resistor, a second resistor and a first capacitor;

[0014] One end of the first resistor and one end of the second resistor are respectively connected to the output end of the power supply, and the other end of the first resistor and the other end of the second resistor are respectively connected to the cathode of the voltage-regulating diode and the end of the current-limiting resistor away from the triode sub-circuit; one end of the first capacitor is connected to the cathode of the voltage-regulating diode, and the other end is connected to the anode of the voltage-regulating diode.

[0015] Preferably, the triode subcircuit comprises a triode;

[0016] The emitter of the triode is connected to the output end of the power supply, the base is connected to the output end of the voltage regulator circuit, and the collector is connected to the second input end of the field effect tube circuit and the grounding resistor respectively;

[0017] When the output voltage of the power supply is lower than the preset voltage, the transistor is turned off;

[0018] When the output voltage of the power supply is greater than or equal to the preset voltage, the transistor is turned on.

[0019] Preferably, the triode sub-circuit further includes a third resistor;

[0020] One end of the third resistor is connected to the output end of the power supply, and the other end is connected to the emitter of the transistor.

[0021] Preferably, the field effect tube sub-circuit includes a field effect tube;

[0022] The source of the field effect transistor is connected to the output terminal of the power supply, the drain is connected to the input terminal of the electronic device, and the gate is connected to the output terminal of the triode sub-circuit and the grounding resistor respectively;

[0023] When the output voltage of the power supply is lower than a preset voltage, the field effect transistor is turned on;

[0024] When the output voltage of the power supply is greater than or equal to the preset voltage, the field effect transistor is turned off.

[0025] Preferably, the field effect tube circuit further includes a fourth resistor and a second capacitor;

[0026] One end of the fourth resistor is connected to the source of the field effect tube, and the other end is connected to the gate of the field effect tube; one end of the second capacitor is connected to the drain of the field effect tube, and the other end is connected to the gate of the field effect tube.

[0027] Preferably, it further comprises a first grounding capacitor and a second grounding capacitor;

[0028] The output end of the power supply is connected to one end of the first grounding capacitor, and the other end of the first grounding capacitor is connected to the ground; the input end of the electronic device is connected to one end of the second grounding capacitor, and the other end of the second grounding capacitor is connected to the ground.

[0029] This application has the following advantages:

[0030] In response to the problem of high production costs of existing overvoltage protection circuits, the present application provides a solution for constructing an overvoltage protection circuit using low-cost discrete components, specifically: an overvoltage protection circuit, including a voltage regulator circuit, a triode circuit, a field-effect tube circuit and a grounding resistor; the first input end of the field-effect tube circuit, the input end of the voltage regulator circuit and the first input end of the triode circuit are respectively connected to the output end of a power supply; the output end of the field-effect tube circuit is connected to the input end of an electronic device; the first output end of the voltage regulator circuit is connected to the second input end of the triode circuit; the output end of the triode circuit is connected to the second input end of the field-effect tube circuit; the voltage regulator circuit The second output end of the circuit is connected to the ground; the output end of the triode sub-circuit and the second input end of the field-effect tube circuit are respectively connected to one end of the grounding resistor, and the other end of the grounding resistor is connected to the ground; when the output voltage of the power supply is less than the preset voltage, the first output end of the voltage-stabilizing tube circuit outputs a high level, the first input end and the output end of the triode circuit are cut off, and the first input end and the output end of the field-effect tube circuit are connected; when the output voltage of the power supply is greater than or equal to the preset voltage, the first output end of the voltage-stabilizing tube circuit outputs a low level, the first input end and the output end of the triode circuit are connected, and the first input end and the output end of the field-effect tube circuit are cut off.

[0031] Through the coordinated cooperation of the voltage-stabilizing tube circuit, the triode circuit and the field-effect tube circuit, conduction can be achieved between the power supply and the electronic device when the power supply voltage is less than the preset voltage, and conduction can be achieved between the power supply and the electronic device when the power supply voltage is greater than or equal to the preset voltage, thereby achieving overvoltage protection. At the same time, the selected electronic components are low-cost, easy to obtain, and convenient to process, which makes the production cost of the overall circuit low and can meet the voltage protection needs of various cost-sensitive consumer electronic products. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for the description of the present application. Obviously, the drawings described below are only part of the embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0033] Figure 1 This is a schematic diagram of the connection relationship of the overvoltage protection circuit provided by the background technology;

[0034] Figure 2 Schematic diagram of the structure of an overvoltage protection circuit provided in one embodiment of the present application.

[0035] The reference numerals in the drawings of the specification are as follows:

[0036] 11. Voltage regulator circuit; 12. Transistor circuit; 13. Field effect tube circuit; 14. Grounding resistor. DETAILED DESCRIPTION

[0037] To make the purposes, features, and advantages of this application more readily apparent, the present application is further described below in detail with reference to the accompanying drawings and specific embodiments. It is apparent that the embodiments described are only a portion of the embodiments of this application, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments in this application without inventive effort are also within the scope of protection of this application.

[0038] By analyzing the existing technology, the inventors found that traditional IC design usually integrates multiple functional modules, such as voltage detection, control feedback, protection triggering, etc., and relies on advanced semiconductor production technology, involving multiple links such as wafer manufacturing, packaging and testing, resulting in its overall production cost being high and unable to meet the voltage protection needs of some cost-sensitive consumer electronic products.

[0039] In view of the above problems, the present application provides a solution for constructing an overvoltage protection circuit using low-cost discrete components.

[0040] Reference Figure 2 In one embodiment of the present application, an overvoltage protection circuit is provided, comprising a voltage regulator circuit 11, a triode circuit 12, a field effect tube circuit 13 and a grounding resistor 14;

[0041] The first input end of the field effect tube circuit 13, the input end of the voltage regulator tube circuit 11, and the first input end of the transistor circuit 12 are respectively connected to the output end of the power supply J24; the output end of the field effect tube circuit 13 is connected to the input end of the electronic device; the first output end of the voltage regulator tube circuit 11 is connected to the second input end of the transistor circuit 12; the output end of the transistor circuit 12 is connected to the second input end of the field effect tube circuit 13; the second output end of the voltage regulator tube circuit 11 is connected to ground; the output end of the transistor circuit 12 and the second input end of the field effect tube circuit 13 are respectively connected to one end of the grounding resistor 14, and the other end of the grounding resistor 14 is connected to ground;

[0042] When the output voltage of the power supply J24 is lower than the preset voltage, the first output terminal of the voltage regulator circuit 11 outputs a high level, the first input terminal and the output terminal of the triode circuit 12 are cut off, and the first input terminal and the output terminal of the field effect tube circuit 13 are connected;

[0043] When the output voltage of the power supply J24 is greater than or equal to the preset voltage, the first output end of the voltage regulator circuit 11 outputs a low level, the first input end and the output end of the transistor circuit 12 are connected, and the first input end and the output end of the field effect tube circuit 13 are cut off.

[0044] Through the coordinated cooperation of the voltage-stabilizing tube circuit 11, the triode circuit 12 and the field-effect tube circuit 13, the power supply J24 and the electronic device can be connected when the power supply voltage is less than the preset voltage, and the power supply J24 and the electronic device can be cut off when the power supply voltage is greater than or equal to the preset voltage, thereby playing the role of overvoltage protection; at the same time, the selected electronic components are low-cost, easy to obtain, and convenient to process, so that the production cost of the overall circuit is low, which can meet the voltage protection needs of various cost-sensitive consumer electronic products.

[0045] Next, the overvoltage protection circuit in this exemplary embodiment will be further described.

[0046] In one embodiment of the present application, the voltage regulator circuit 11 includes a voltage regulator D39 and a current limiting resistor R684;

[0047] The cathode of the voltage-stabilizing diode D39 and one end of the current-limiting resistor R684 are respectively connected to the output end of the power supply J24, the anode of the voltage-stabilizing diode D39 is connected to the ground, and the other end of the current-limiting resistor R684 is connected to the second input end of the triode sub-circuit 12;

[0048] When the output voltage of the power supply J24 is lower than the preset voltage, the voltage regulator D39 is turned off, and the end of the current limiting resistor R684 connected to the transistor sub-circuit 12 outputs a high level;

[0049] When the output voltage of the power supply J24 is greater than or equal to the preset voltage, the voltage regulator D39 is turned on, and the end of the current limiting resistor R684 connected to the transistor sub-circuit 12 outputs a low level.

[0050] The function of the voltage-stabilizing diode D39 and the current-limiting resistor R684 is to monitor the power supply voltage, control the conduction state of the voltage-stabilizing diode D39 through the voltage of the voltage-stabilizing diode D39, and then control the level of the current-limiting resistor R684, and then control the switching state of the transistor circuit 12 and the field-effect transistor circuit 13.

[0051] In one embodiment of the present application, the voltage regulator circuit 11 further includes a first resistor R680, a second resistor R681 and a first capacitor C536;

[0052] One end of the first resistor R680 and one end of the second resistor R681 are respectively connected to the output end of the power supply J24, and the other end of the first resistor R680 and the other end of the second resistor R681 are connected to the cathode of the voltage-regulating diode D39 and the end of the current-limiting resistor R684 away from the triode sub-circuit 12 respectively; one end of the first capacitor C536 is connected to the cathode of the voltage-regulating diode D39, and the other end is connected to the anode of the voltage-regulating diode D39.

[0053] One end of the first resistor R680 and the second resistor R681 form a voltage divider network to adjust the voltage distribution in the circuit and ensure that the Zener diode D39 conducts under appropriate conditions. The first capacitor C536 is used to filter out high-frequency noise between the cathode and anode of the Zener diode D39, making the voltage signal more stable and ensuring the stable operation of the Zener diode D39.

[0054] In one embodiment of the present application, the transistor sub-circuit 12 includes a transistor Q15;

[0055] The emitter of the transistor Q15 is connected to the output end of the power supply J24, the base is connected to the output end of the voltage regulator circuit 11, and the collector is connected to the second input end of the field effect tube circuit 13 and one end of the grounding resistor 14 respectively;

[0056] When the output voltage of the power supply J24 is lower than the preset voltage, the transistor Q15 is turned off;

[0057] When the output voltage of the power supply J24 is greater than or equal to the preset voltage, the transistor Q15 is turned on.

[0058] The transistor Q15 is the first switching element in the voltage protection circuit. The voltage level input to the base of the transistor Q15 controls the conduction state of the transistor Q15, and further controls the switching state of the field effect transistor circuit 13.

[0059] In one embodiment of the present application, the triode sub-circuit 12 further includes a third resistor R682;

[0060] One end of the third resistor R682 is connected to the output end of the power supply J24, and the other end is connected to the emitter of the transistor Q15.

[0061] The third resistor R682 is used to adjust the voltage distribution in the circuit to ensure that the transistor Q15 is turned on under appropriate conditions.

[0062] In one embodiment of the present application, the field effect tube circuit 13 includes a field effect tube Q14;

[0063] The source of the field effect transistor Q14 is connected to the output terminal of the power supply J24, the drain is connected to the input terminal of the electronic device, and the gate is connected to the output terminal of the triode sub-circuit 12 and one end of the grounding resistor 14 respectively;

[0064] When the output voltage of the power supply J24 is lower than the preset voltage, the field effect transistor Q14 is turned on;

[0065] When the output voltage of the power supply J24 is greater than or equal to the preset voltage, the field effect transistor Q14 is turned off.

[0066] The field effect transistor Q14 is a second switch element in the voltage protection circuit. The level of the voltage input to the gate of the field effect transistor Q14 controls the conduction state of the field effect transistor Q14.

[0067] In one embodiment of the present application, the field effect transistor circuit 13 further includes a fourth resistor R678 and a second capacitor C528;

[0068] One end of the fourth resistor R678 is connected to the source of the field effect transistor Q14, and the other end is connected to the gate of the field effect transistor Q14; one end of the second capacitor C528 is connected to the drain of the field effect transistor Q14, and the other end is connected to the gate of the field effect transistor Q14.

[0069] The fourth resistor R678 is used to adjust the voltage distribution in the circuit to ensure that the FET Q14 is turned on under appropriate conditions. The second capacitor C528 is used to filter out high-frequency noise between the gate and drain of the FET Q14, making the voltage signal more stable and ensuring the stable operation of the FET Q14.

[0070] In one embodiment of the present application, a first grounding capacitor C526 and a second grounding capacitor C527 are further included;

[0071] The output end of the power supply J24 is connected to one end of the first grounding capacitor C526, and the other end of the first grounding capacitor C526 is connected to the ground; the input end of the electronic device is connected to one end of the second grounding capacitor C527, and the other end of the second grounding capacitor C527 is connected to the ground.

[0072] The first grounding capacitor C526 and the second grounding capacitor C527 are used to filter out high-frequency noise and ensure stable current transmission between the power supply J24 and the electronic device.

[0073] In a specific implementation of the present application, the overvoltage protection circuit includes a voltage regulator D39 (breakdown voltage of 14V), a current limiting resistor R684 (resistance of 1KΩ), a first resistor R680 (resistance of 1KΩ), a second resistor R681 (resistance of 1KΩ), a first capacitor C536 (capacity of 0.1μF, rated voltage of 16V), a transistor Q15, a third resistor R682 (resistance of 0Ω), a field effect transistor Q14 (gate-source voltage threshold value <-2.6V@17A), a fourth resistor R678 (resistance of 200KΩ), a second capacitor C528 (capacity of 100pF, rated voltage of 50V), a grounding resistor 14 (resistance of 10KΩ), a first grounding capacitor C526 (capacity of 47μF, rated voltage of 16V), and a second grounding capacitor C527 (capacity of 47μF, rated voltage of 16V);

[0074] The cathode of the voltage-stabilizing tube D39 and one end of the current-limiting resistor R684 are respectively connected to the output end of the power supply J24 (output voltage is 12V or 24V), the anode of the voltage-stabilizing tube D39 is connected to the ground, and the other end of the current-limiting resistor R684 is connected to the base of the transistor Q15;

[0075] One end of the first resistor R680 and one end of the second resistor R681 are respectively connected to the output end of the power supply J24. The other end of the first resistor R680 and the other end of the second resistor R681 are connected, and then respectively connected to the cathode of the voltage-stabilizing diode D39 and the end of the current-limiting resistor R684 away from the transistor Q15. One end of the first capacitor C536 is connected to the cathode of the voltage-stabilizing diode D39, and the other end is connected to the anode of the voltage-stabilizing diode D39.

[0076] The emitter of the transistor Q15 is connected to the output end of the power supply J24, and the collector is connected to the gate of the field effect transistor Q14 and one end of the grounding resistor 14 respectively;

[0077] One end of the third resistor R682 is connected to the output end of the power supply J24, and the other end is connected to the emitter of the transistor Q15;

[0078] The source of the field effect transistor Q14 is connected to the output terminal of the power supply J24, the drain is connected to the input terminal of the electronic device, and the gate is connected to one end of the grounding resistor 14;

[0079] One end of the fourth resistor R678 is connected to the source of the field effect transistor Q14, and the other end is connected to the gate of the field effect transistor Q14; one end of the second capacitor C528 is connected to the drain of the field effect transistor Q14, and the other end is connected to the gate of the field effect transistor Q14;

[0080] The other end of the grounding resistor 14 is connected to the ground;

[0081] The output end of the power supply J24 is connected to one end of the first grounding capacitor C526, and the other end of the first grounding capacitor C526 is connected to the ground;

[0082] The input terminal of the electronic device is connected to one end of the second grounding capacitor C527, and the other end of the second grounding capacitor C527 is connected to the ground;

[0083] When the output voltage of the power supply J24 is less than 14V, the voltage regulator D39 is turned off, the current limiting resistor R684 outputs a high level to the base of the transistor Q15, the transistor Q15 is turned off, the collector of the transistor Q15 outputs a low level to the gate of the field effect transistor Q14, the field effect transistor Q14 is turned on, and the power supply J24 and the electronic device are connected;

[0084] When the output voltage of the power supply J24 is greater than or equal to 14V, the voltage regulator D39 is turned on (broken down), the current limiting resistor R684 outputs a low level to the base of the transistor Q15, the transistor Q15 is turned on, the collector of the transistor Q15 outputs a high level to the gate of the field effect transistor Q14, the field effect transistor Q14 is turned off, and the power supply J24 and the electronic device are turned off.

[0085] The above embodiments are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to in detail.

[0086] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concepts. Therefore, the interpretation of the appended claims includes the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present application.

[0087] Finally, it should be noted that in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, an element defined by the sentence "comprises a..." does not exclude the presence of additional identical elements in the process, method, article or terminal device that includes the element.

[0088] The above is a detailed introduction to an overvoltage protection circuit provided by this application. Specific embodiments are used in this specification to illustrate the principles and implementation methods of this application. The description of the above embodiments is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the contents of this specification should not be understood as limiting this application.

Claims

1. An overvoltage protection circuit, characterized in that: Including voltage regulator tube circuit, triode tube circuit, field effect tube circuit and grounding resistor; The first input end of the field effect tube circuit, the input end of the voltage regulator tube circuit, and the first input end of the triode circuit are respectively connected to the output end of the power supply; the output end of the field effect tube circuit is connected to the input end of the electronic device; the first output end of the voltage regulator tube circuit is connected to the second input end of the triode circuit; the output end of the triode circuit is connected to the second input end of the field effect tube circuit; the second output end of the voltage regulator tube circuit is connected to ground; the output end of the triode circuit and the second input end of the field effect tube circuit are respectively connected to one end of the grounding resistor, and the other end of the grounding resistor is connected to ground; When the output voltage of the power supply is lower than the preset voltage, the first output terminal of the voltage regulator circuit outputs a high level, the first input terminal and the output terminal of the triode circuit are cut off, and the first input terminal and the output terminal of the field effect tube circuit are connected; When the output voltage of the power supply is greater than or equal to the preset voltage, the first output end of the voltage regulator circuit outputs a low level, the first input end and the output end of the transistor circuit are connected, and the first input end and the output end of the field effect tube circuit are cut off.

2. The overvoltage protection circuit according to claim 1, wherein: The voltage-stabilizing tube circuit includes a voltage-stabilizing tube and a current-limiting resistor; The cathode of the voltage-stabilizing diode and one end of the current-limiting resistor are respectively connected to the output end of the power supply, the anode of the voltage-stabilizing diode is connected to the ground, and the other end of the current-limiting resistor is connected to the second input end of the triode sub-circuit; When the output voltage of the power supply is lower than the preset voltage, the voltage regulator is turned off, and the end of the current limiting resistor connected to the transistor subcircuit outputs a high level; When the output voltage of the power supply is greater than or equal to the preset voltage, the voltage regulator is turned on, and the end of the current limiting resistor connected to the transistor subcircuit outputs a low level.

3. The overvoltage protection circuit according to claim 2, wherein: The voltage regulator circuit also includes a first resistor, a second resistor and a first capacitor; One end of the first resistor and one end of the second resistor are respectively connected to the output end of the power supply, and the other end of the first resistor and the other end of the second resistor are respectively connected to the cathode of the voltage-regulating diode and the end of the current-limiting resistor away from the triode sub-circuit; one end of the first capacitor is connected to the cathode of the voltage-regulating diode, and the other end is connected to the anode of the voltage-regulating diode.

4. The overvoltage protection circuit according to claim 1, wherein: The triode subcircuit includes a triode; The emitter of the triode is connected to the output end of the power supply, the base is connected to the output end of the voltage regulator circuit, and the collector is connected to the second input end of the field effect tube circuit and the grounding resistor respectively; When the output voltage of the power supply is lower than the preset voltage, the transistor is turned off; When the output voltage of the power supply is greater than or equal to the preset voltage, the transistor is turned on.

5. The overvoltage protection circuit according to claim 4, characterized in that: The triode subcircuit further includes a third resistor; One end of the third resistor is connected to the output end of the power supply, and the other end is connected to the emitter of the transistor.

6. The overvoltage protection circuit according to claim 1, wherein: The field effect tube circuit includes a field effect tube; The source of the field effect transistor is connected to the output terminal of the power supply, the drain is connected to the input terminal of the electronic device, and the gate is connected to the output terminal of the triode sub-circuit and the grounding resistor respectively; When the output voltage of the power supply is lower than a preset voltage, the field effect transistor is turned on; When the output voltage of the power supply is greater than or equal to the preset voltage, the field effect transistor is turned off.

7. The overvoltage protection circuit according to claim 6, characterized in that: The field effect tube circuit further includes a fourth resistor and a second capacitor; One end of the fourth resistor is connected to the source of the field effect tube, and the other end is connected to the gate of the field effect tube; one end of the second capacitor is connected to the drain of the field effect tube, and the other end is connected to the gate of the field effect tube.

8. The overvoltage protection circuit according to claim 1, wherein: Also includes a first grounding capacitor and a second grounding capacitor; The output end of the power supply is connected to one end of the first grounding capacitor, and the other end of the first grounding capacitor is connected to the ground; the input end of the electronic device is connected to one end of the second grounding capacitor, and the other end of the second grounding capacitor is connected to the ground.

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