Power input overvoltage protection circuit, power supply and electronic equipment

Abstract

The utility model relates to a power supply input overvoltage protection circuit, a power supply and electronic equipment. The circuit comprises an input voltage sampling unit, a driving voltage generation unit, a driving voltage turn-off unit and a power supply output switch unit, the input voltage sampling unit is connected with the power supply input circuit and generates sampling voltage; the driving voltage generation unit is connected with the power input circuit and generates driving voltage; the power output switch unit is connected with the driving voltage generation unit and the power output circuit, and receives the driving voltage to conduct the power output of the power output circuit; the driving voltage turn-off unit is connected with the input voltage sampling unit and the driving voltage generating unit, and receives the sampling voltage to turn on or turn off the driving voltage; the input voltage sampling unit is connected with the driving voltage generation unit and is used for generating a first sampling voltage when receiving the driving voltage, or generating a second sampling voltage. The power supply input overvoltage protection circuit can realize power supply input overvoltage protection through a simple circuit so as to reduce circuit cost.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply, and more specifically to a power input overvoltage protection circuit, a power supply and an electronic device. Background Art

[0002] Due to peak power consumption and cable transmission, AC voltage will fluctuate, especially in remote areas. When the input voltage exceeds the upper limit of the input voltage allowed by the electrical equipment, the electrical equipment may be damaged. Therefore, an overvoltage protection device is usually set in the AC input, so that when the input voltage exceeds the upper limit of the input voltage allowed by the electrical equipment, the input voltage can be cut off in time to protect the electrical equipment; when the input voltage falls back to the safe voltage, the protection device automatically resumes power supply to the electrical equipment to avoid unnecessary losses and dangers. However, part of the existing switching power supplies for electrical equipment do not have input overvoltage protection design, and part of them only add simple protection elements such as overvoltage protectors or fuses at the AC input end, which is difficult to play a protective role when the power grid is relatively unstable. In addition, the use of AC contactors to disconnect the loop between the AC input and the load has the disadvantages of large size, high cost, and inconvenient installation. Even if other switching power supplies are designed with input overvoltage protection voltage, they are difficult to promote and apply due to high cost, the need for additional auxiliary power supply, MCU control, and complex design. At the same time, when the PWM output of the IC is turned off to protect the electrical equipment, it only makes the electrical equipment stop working, but the electrical equipment still has to withstand high voltage input, which poses certain safety hazards. If it needs to be implemented through a single-chip microcomputer, an auxiliary power supply is required, and the design is complex and the cost is high. Utility Model Content

[0003] The technical problem to be solved by the utility model is to provide a power input overvoltage protection circuit, a power supply and an electronic device in view of the above-mentioned technical defects of the prior art.

[0004] The technical solution adopted by the utility model to solve the technical problem is: constructing a power input overvoltage protection circuit, including: an input voltage sampling unit, a driving voltage generating unit, a driving voltage shutoff unit and a power output switch unit;

[0005] The input voltage sampling unit is used to connect to the power input circuit, and is used to generate a sampling voltage according to the power input of the power input circuit;

[0006] The driving voltage generating unit is used to connect to the power input circuit to generate a driving voltage;

[0007] The power output switch unit is connected to the driving voltage generating unit and the power output circuit, and is used to receive the driving voltage to turn on the power output of the power output circuit;

[0008] The driving voltage shutoff unit is connected to the input voltage sampling unit and the driving voltage generating unit, and is used to receive the sampling voltage to turn on or off the driving voltage of the driving voltage generating unit;

[0009] The input voltage sampling unit is also connected to the driving voltage generating unit, and is used to generate a first sampling voltage when receiving the driving voltage, and otherwise generate a second sampling voltage.

[0010] Preferably, in the power input overvoltage protection circuit of the utility model, the input voltage sampling unit includes a first voltage dividing circuit, a second voltage dividing circuit, a third voltage dividing circuit and a switch circuit;

[0011] A first end of the first voltage divider circuit is connected to the power input circuit, a second end of the first voltage divider circuit is connected to a first end of the second voltage divider circuit, a first end of the third voltage divider circuit and the drive voltage shut-off unit, a second end of the third voltage divider circuit is connected to a first end of the switch circuit, a control end of the switch circuit is connected to an output end of the drive voltage generating unit, and a second end of the switch circuit and a second end of the second voltage divider circuit are connected to a ground of the power output circuit.

[0012] Preferably, in the power input overvoltage protection circuit of the utility model, the switch circuit includes a first MOS tube, a first resistor and a second resistor;

[0013] The gate of the first MOS tube is connected to the first end of the first resistor and the first end of the second resistor, the drain of the first MOS tube is connected to the second end of the third voltage divider circuit, the source of the first MOS tube and the second end of the first resistor are connected to the ground of the power output circuit, and the second end of the second resistor is connected to the output end of the driving voltage generating unit.

[0014] Preferably, in the power input overvoltage protection circuit of the utility model, the power input is an AC input, and the input voltage sampling unit further includes a rectifier circuit;

[0015] The first end of the rectifier circuit is connected to the L input of the AC input, the second end of the rectifier circuit is connected to the N input of the AC input, and the third end of the rectifier circuit is connected to the first end of the first voltage divider circuit.

[0016] Preferably, in the power input overvoltage protection circuit of the utility model, the rectifier circuit includes a first diode and a second diode;

[0017] An anode of the first diode is connected to the L input, an anode of the second diode is connected to the N input, and a cathode of the first diode and a cathode of the second diode are connected to a first end of the first voltage divider circuit.

[0018] Preferably, in the power input overvoltage protection circuit of the utility model, the driving voltage generating unit includes: a first capacitor, a second capacitor, a third diode, a voltage stabilizing diode, a third resistor and a fourth resistor;

[0019] The first end of the third resistor is connected to the power input, the second end of the third resistor is connected to the first end of the first capacitor, the second end of the first capacitor is connected to the anode of the third diode, the cathode of the third diode is connected to the first end of the second capacitor, the cathode of the Zener diode and the first end of the fourth resistor, the second end of the second capacitor and the anode of the Zener diode are connected to the ground of the power output circuit, and the second end of the fourth resistor is the output end of the driving voltage generating unit.

[0020] Preferably, in the power input overvoltage protection circuit described in the utility model, the driving voltage shutdown unit includes a controllable voltage stabilizing chip and a sampling voltage conditioning circuit;

[0021] The reference end of the controllable voltage stabilizing chip is connected to the first end of the sampling voltage conditioning, the second end of the sampling voltage conditioning is connected to the output end of the input voltage sampling unit, the anode of the controllable voltage stabilizing chip is connected to the ground of the power output circuit, and the cathode of the controllable voltage stabilizing chip is connected to the output end of the driving voltage generating unit.

[0022] Preferably, in the power input overvoltage protection circuit of the utility model, the power output switch unit includes a second MOS tube, a fifth resistor and a sixth resistor;

[0023] The gate of the second MOS tube is connected to the first end of the fifth resistor and the first end of the sixth resistor, the source of the second MOS tube is connected to the second end of the sixth resistor and the ground of the power output circuit, the drain of the second MOS tube is used to connect the ground of the load, and the second end of the fifth resistor is connected to the output end of the driving voltage generating unit.

[0024] The utility model also constructs a power supply, comprising a power input circuit, a power output circuit and a power input overvoltage protection circuit as described in any one of the above.

[0025] The utility model also constructs an electronic device, comprising: the power supply as described above.

[0026] The implementation of the power input overvoltage protection circuit, power supply and electronic equipment of the utility model has the following beneficial effects: power input overvoltage protection is achieved through a simple circuit, the circuit structure is simple, and the circuit cost can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0028] Figure 1 It is a structural schematic diagram of an embodiment of a power input overvoltage protection circuit of the utility model;

[0029] Figure 2 The utility model is a circuit schematic diagram of an embodiment of a power input overvoltage protection circuit. DETAILED DESCRIPTION

[0030] In order to have a clearer understanding of the technical features, purposes and effects of the present utility model, the specific implementation methods of the present utility model are now described in detail with reference to the accompanying drawings.

[0031] like Figure 1As shown, in a first embodiment of a power input overvoltage protection circuit of the utility model, it includes: an input voltage sampling unit 110, a driving voltage generating unit 120, a driving voltage shutoff unit 130 and a power output switch unit 140; the input voltage sampling unit 110 is used to connect the power input circuit 210, and is used to generate a sampling voltage according to the power input of the power input circuit 210; the driving voltage generating unit 120 is used to connect the power input circuit 210 to generate a driving voltage; the power output switch unit 140 is connected to the driving voltage generating unit 120 and the power output circuit 220, and is used to receive the driving voltage to turn on the power output of the power output circuit 220; the driving voltage shutoff unit 130 is connected to the input voltage sampling unit 110 and the driving voltage generating unit 120, and is used to receive the sampling voltage to turn on or shut off the driving voltage of the driving voltage generating unit 120; the input voltage sampling unit 110 is also connected to the driving voltage generating unit 120, and is used to generate a first sampling voltage when receiving the driving voltage, otherwise it generates a second sampling voltage. Specifically, the input voltage sampling unit 110 samples the power input of the power input circuit 210 to obtain a corresponding sampling voltage. The driving voltage generating unit 120 obtains the driving voltage after conversion according to the power input of the power input circuit 210. When the driving voltage is normal, the power output switch unit 140 receives the driving voltage and turns on, and the power output of the power output circuit 220 is normal. When the power input of the power input circuit 210 is normal, the sampling voltage obtained by the input voltage sampling unit 110 is also normal. The driving voltage shutoff unit 130 does not act when receiving the normal sampling voltage. At this time, the driving voltage generating unit 120 is in a normal output state. When the power input of the power input circuit 210 is too high, the sampling voltage obtained by the input voltage sampling unit 110 will become higher and reach a preset threshold value. At this time, the higher sampling voltage causes the driving voltage shutoff unit 130 to act to shut off the driving voltage of the driving voltage generating unit 120. When the driving voltage is turned off, the power output switch unit 140 switches to the off state, and the power output of the power output circuit 220 is turned off. When the input voltage sampling unit 110 receives the driving voltage generated by the driving voltage generating unit 120, it switches to the first working mode and outputs the first sampling voltage accordingly. When the driving voltage is turned off, the input voltage sampling unit 110 enters the second working mode and outputs the second sampling voltage accordingly. The second sampling voltage will be higher than the first sampling voltage. In this way, when the first sampling voltage reaches the action threshold of the driving voltage shutoff unit 130, the sampling voltage of the input voltage sampling unit 110 is further raised through the shutoff action of the driving voltage shutoff unit 130 to be higher than the action threshold of the driving voltage shutoff unit 130, so that the driving voltage shutoff unit 130 is stably maintained in the shutoff state, ensuring that the power output of the power output circuit 220 is in the shutoff state, and improving the reliability of circuit protection.At the same time, in order to enable the driving voltage shutoff unit 130 to restore the driving voltage output of the driving voltage generating unit 120, the input voltage at the power input terminal is reduced so that the second sampling voltage is lower than the trigger threshold of the driving voltage shutoff unit 130. At this time, the driving voltage shutoff unit 130 restores the driving voltage output of the driving voltage generating unit 120, and the power output switch unit 140 switches to the on state. The input voltage sampling unit 110 resumes obtaining the first sampling voltage. Since the first sampling voltage is less than the second sampling voltage, the driving voltage shutoff unit 130 continues to output the driving voltage of the driving voltage generating unit 120. The power output switch unit 140 is not turned off and turned on at the same point, forming a hysteresis, thereby improving the reliability of the circuit.

[0032] Optional, such as Figure 2 As shown, the input voltage sampling unit 110 includes a first voltage divider circuit, a second voltage divider circuit, a third voltage divider circuit and a switch circuit; the first end of the first voltage divider circuit is connected to the power input circuit 210, the second end of the first voltage divider circuit is connected to the first end of the second voltage divider circuit, the first end of the third voltage divider circuit and the driving voltage shutoff unit 130, the second end of the third voltage divider circuit is connected to the first end of the switch circuit, the control end of the switch circuit is connected to the output end of the driving voltage generating unit 120, and the second end of the switch circuit and the second end of the second voltage divider circuit are connected to the ground of the power output circuit 220. Specifically, in the input voltage sampling unit 110, under normal circumstances, the driving voltage of the driving voltage generating unit 120 is output normally, and the switch circuit receives the driving voltage and remains in the on state. When the switch circuit is turned on, the second voltage divider circuit is connected in parallel with the third voltage divider circuit and then connected in series with the first voltage divider circuit to divide the input voltage of the power input and output the sampling voltage, i.e., the first sampling voltage, at the series connection node. When the first sampling voltage is higher than the threshold value of the driving voltage shutoff unit 130, the driving voltage output of the driving voltage generating unit 120 is shut off, the switch circuit is switched to the shutoff state, and the second voltage divider circuit is connected in series with the first voltage divider circuit to divide the input voltage of the power supply input and output the sampling voltage, i.e., the second sampling voltage, at the series connection node. At this time, since the second voltage divider circuit is no longer connected in parallel with the third voltage divider circuit, the voltage divider resistance of the second voltage divider circuit becomes larger, and the obtained second sampling voltage will also be greater than the first sampling voltage, maintaining the driving voltage shutoff unit 130 in the shutoff state.

[0033] In one embodiment, the first voltage divider circuit may be composed of a single resistor or a plurality of resistors connected in series and / or in parallel, for example, a resistor R57, a resistor R58, and a resistor R59 connected in series. The second voltage divider circuit may also be composed of a single resistor or a plurality of resistors. For example, the second voltage divider circuit is formed by a resistor R60. The third voltage divider circuit may also be composed of a single resistor or a plurality of resistors. For example, the third voltage divider circuit is formed by a resistor R61.

[0034] Optionally, the switch circuit includes a first MOS transistor, a first resistor, and a second resistor; the gate of the first MOS transistor is connected to the first end of the first resistor and the first end of the second resistor, the drain of the first MOS transistor is connected to the second end of the third voltage divider circuit, the source of the first MOS transistor and the second end of the first resistor are connected to the ground of the power output circuit 220, and the second end of the second resistor is connected to the output end of the driving voltage generating unit 120. Specifically, in the switch circuit, the first MOS transistor includes a MOS transistor Q202, the first resistor includes a resistor R5, and the second resistor includes a resistor R62. The driving voltage output from the output end of the driving voltage generating unit 120 drives the MOS transistor Q202 to turn on through the resistor R62. When the driving voltage is turned off, the MOS transistor Q202 is turned off.

[0035] Optionally, the power input is an AC input, and the input voltage sampling unit 110 further includes a rectifier circuit; the first end of the rectifier circuit is connected to the L input of the AC input, the second end of the rectifier circuit is connected to the N input of the AC input, and the third end of the rectifier circuit is connected to the first end of the first voltage divider circuit. Specifically, when the power input in the power input circuit 210 is an AC input, a rectifier circuit is further provided in the input voltage sampling unit 110 to rectify the AC input to obtain a DC sampling voltage. The first end of the rectifier circuit is connected to the L input of the AC input, the second end of the rectifier circuit is connected to the N input of the AC input, and the third end of the rectifier circuit, i.e., the output end, is connected to the first end of the first voltage divider circuit.

[0036] Further, the rectifier circuit includes a first diode and a second diode; the anode of the first diode is connected to the L input, the anode of the second diode is connected to the N input, and the cathode of the first diode and the cathode of the second diode are connected to the first end of the first voltage divider circuit. Specifically, in the rectifier circuit, the first diode includes a diode D8, and the second diode includes a diode D9. The anode of the diode D8 and the anode of the diode D9 are respectively connected to the L input and the N input of the AC input to realize the rectification of the AC input, and the DC voltage is output at the cathode of the diode D8 and the cathode of the diode D9.

[0037] Optionally, the driving voltage generating unit 120 includes: a first capacitor, a second capacitor, a third diode, a voltage-stabilizing diode, a third resistor, and a fourth resistor; the first end of the third resistor is connected to the power input, the second end of the third resistor is connected to the first end of the first capacitor, the second end of the first capacitor is connected to the anode of the third diode, the cathode of the third diode is connected to the first end of the second capacitor, the cathode of the voltage-stabilizing diode, and the first end of the fourth resistor, the second end of the second capacitor and the anode of the voltage-stabilizing diode are connected to the ground of the power output circuit 220, and the second end of the fourth resistor is the output end of the driving voltage generating unit 120. Specifically, in the driving voltage generating unit 120, the first capacitor includes a capacitor C1, the second capacitor includes a capacitor CE501, the third diode includes a diode D305, the voltage-stabilizing diode includes a voltage-stabilizing diode ZD2, the third resistor includes a resistor R12, and the fourth resistor includes a resistor R8. The resistor R12, the capacitor C1, the diode D305, the capacitor CE501 and the voltage-stabilizing diode ZD2 can obtain a DC voltage within a preset range, such as a DC voltage of 12V-18V, by using the principle of resistance-capacitance voltage reduction, and supply power to the controllable voltage-stabilizing chip U4 through the resistor R8, and output a corresponding driving voltage at the second end of the resistor R8. The driving voltage generating unit 120 can obtain the input voltage from the subsequent power input in the power input circuit.

[0038] Optionally, the driving voltage shutoff unit 130 includes a controllable voltage stabilizing chip and a sampling voltage conditioning circuit; the reference end of the controllable voltage stabilizing chip is connected to the first end of the sampling voltage conditioning, the second end of the sampling voltage conditioning is connected to the output end of the input voltage sampling unit 110, the anode of the controllable voltage stabilizing chip is connected to the ground of the power output circuit 220, and the cathode of the controllable voltage stabilizing chip is connected to the output end of the driving voltage generating unit 120. Specifically, the driving voltage shutoff unit 130 includes a controllable voltage stabilizing chip U4, and the sampling voltage is conditioned by the sampling voltage conditioning circuit and then input to the controllable voltage stabilizing chip U4. When the sampling voltage conditioning circuit outputs a low level, the A and K pins of the controllable voltage stabilizing chip U4 are cut off, the K pin voltage is a high level, and the output end of the driving voltage generating unit 120 outputs the driving voltage normally. When the sampling voltage conditioning circuit output is greater than a preset value, such as 2.5V, the A and K pins of the controllable voltage stabilizing chip U4 are turned on, the K pin voltage is pulled down, the output end of the driving voltage generating unit 120 is pulled down, and the driving voltage is turned off. In one embodiment, the sampling voltage conditioning circuit may include capacitor C209, resistor R32, resistor R207 and capacitor C11. The sampling voltage is filtered by capacitor C209, and then divided and filtered by resistor R32, resistor R207 and capacitor C11 to obtain the regulated sampling voltage which is input to the reference end of the controllable voltage stabilizing chip U4, which is also the reference end.

[0039] Optionally, the power output switch unit 140 includes a second MOS transistor, a fifth resistor, and a sixth resistor; the gate of the second MOS transistor is connected to the first end of the fifth resistor and the first end of the sixth resistor, the source of the second MOS transistor is connected to the ground of the power output circuit 220, the drain of the second MOS transistor is used to connect the ground of the load, and the second end of the fifth resistor is connected to the output end of the driving voltage generating unit 120. Specifically, in the power output switch unit 140, the second MOS transistor may include a MOS transistor Q9, the fifth resistor includes a resistor R44, and the sixth resistor includes a resistor R50. The driving voltage output by the driving voltage generating unit 120 drives the MOS transistor Q9 to turn on through the resistor R44, so that the power output circuit 220 supplies power to the load 300. When the driving voltage is turned off, the gate of the MOS transistor Q9 is pulled down, the MOS transistor Q9 is turned off, and the power output circuit 220 turns off the output of the load 300.

[0040] A power supply of the utility model includes a power input circuit 210, a power output circuit 220 and a power input overvoltage protection circuit as any one of the above. Specifically, in the power supply, the power supply is protected by the above-mentioned power overvoltage protection circuit. The power output circuit 220 is used to connect the load 300, and the power supply process to the load 300 is controlled by the power output switch unit 140 to turn on or off. The power output circuit 220 may include a power conversion unit to convert the power input of the power input circuit 210. The power supply structure formed by the power input circuit 210 and the power output circuit 220 may include a flyback topology, a forward FORWARD, a boost BOOST, a buck BUCK, a push-pull, a half-bridge, a full-bridge, etc.

[0041] An electronic device of the utility model comprises the above power supply, that is, the above power supply is arranged in the electronic device to supply power, so as to improve the power supply reliability of the whole electronic device.

[0042] It can be understood that the above embodiments only express the preferred implementation methods of the utility model, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the patent scope of the utility model. It should be pointed out that, for ordinary technicians in this field, without departing from the concept of the utility model, the above-mentioned technical features can be freely combined, and several deformations and improvements can be made, which all belong to the protection scope of the utility model. Therefore, all equivalent changes and modifications made to the scope of the claims of the utility model should belong to the scope covered by the claims of the utility model.

Claims

1. A power input overvoltage protection circuit, characterized in that: include: An input voltage sampling unit, a driving voltage generating unit, a driving voltage shutoff unit and a power output switching unit; The input voltage sampling unit is used to connect to the power input circuit, and is used to generate a sampling voltage according to the power input of the power input circuit; The driving voltage generating unit is used to connect to the power input circuit to generate a driving voltage; The power output switch unit is connected to the driving voltage generating unit and the power output circuit, and is used to receive the driving voltage to turn on the power output of the power output circuit; The driving voltage shutoff unit is connected to the input voltage sampling unit and the driving voltage generating unit, and is used to receive the sampling voltage to turn on or off the driving voltage of the driving voltage generating unit; The input voltage sampling unit is also connected to the driving voltage generating unit, and is used to generate a first sampling voltage when receiving the driving voltage, and otherwise generate a second sampling voltage.

2. The power input overvoltage protection circuit according to claim 1, characterized in that: The input voltage sampling unit includes a first voltage dividing circuit, a second voltage dividing circuit, a third voltage dividing circuit and a switch circuit; A first end of the first voltage divider circuit is connected to the power input circuit, a second end of the first voltage divider circuit is connected to a first end of the second voltage divider circuit, a first end of the third voltage divider circuit and the drive voltage shut-off unit, a second end of the third voltage divider circuit is connected to a first end of the switch circuit, a control end of the switch circuit is connected to an output end of the drive voltage generating unit, and a second end of the switch circuit and a second end of the second voltage divider circuit are connected to a ground of the power output circuit.

3. The power input overvoltage protection circuit according to claim 2, characterized in that: The switch circuit includes a first MOS tube, a first resistor and a second resistor; The gate of the first MOS tube is connected to the first end of the first resistor and the first end of the second resistor, the drain of the first MOS tube is connected to the second end of the third voltage divider circuit, the source of the first MOS tube and the second end of the first resistor are connected to the ground of the power output circuit, and the second end of the second resistor is connected to the output end of the driving voltage generating unit.

4. The power input overvoltage protection circuit according to claim 2, characterized in that: The power input is an AC input, and the input voltage sampling unit further includes a rectifier circuit; The first end of the rectifier circuit is connected to the L input of the AC input, the second end of the rectifier circuit is connected to the N input of the AC input, and the third end of the rectifier circuit is connected to the first end of the first voltage divider circuit.

5. The power input overvoltage protection circuit according to claim 4, characterized in that: The rectifier circuit includes a first diode and a second diode; An anode of the first diode is connected to the L input, an anode of the second diode is connected to the N input, and a cathode of the first diode and a cathode of the second diode are connected to a first end of the first voltage divider circuit.

6. The power input overvoltage protection circuit according to claim 4, characterized in that: The driving voltage generating unit includes: a first capacitor, a second capacitor, a third diode, a voltage stabilizing diode, a third resistor and a fourth resistor; The first end of the third resistor is connected to the power input, the second end of the third resistor is connected to the first end of the first capacitor, the second end of the first capacitor is connected to the anode of the third diode, the cathode of the third diode is connected to the first end of the second capacitor, the cathode of the Zener diode and the first end of the fourth resistor, the second end of the second capacitor and the anode of the Zener diode are connected to the ground of the power output circuit, and the second end of the fourth resistor is the output end of the driving voltage generating unit.

7. The power input overvoltage protection circuit according to claim 1, characterized in that: The driving voltage shutoff unit includes a controllable voltage stabilizing chip and a sampling voltage conditioning circuit; The reference end of the controllable voltage stabilizing chip is connected to the first end of the sampling voltage conditioning, the second end of the sampling voltage conditioning is connected to the output end of the input voltage sampling unit, the anode of the controllable voltage stabilizing chip is connected to the ground of the power output circuit, and the cathode of the controllable voltage stabilizing chip is connected to the output end of the driving voltage generating unit.

8. The power input overvoltage protection circuit according to claim 1, characterized in that: The power output switch unit includes a second MOS tube, a fifth resistor and a sixth resistor; The gate of the second MOS tube is connected to the first end of the fifth resistor and the first end of the sixth resistor, the source of the second MOS tube is connected to the second end of the sixth resistor and the ground of the power output circuit, the drain of the second MOS tube is used to connect the ground of the load, and the second end of the fifth resistor is connected to the output end of the driving voltage generating unit.

9. A power supply, characterized in that: It comprises a power input circuit, a power output circuit and a power input overvoltage protection circuit as claimed in any one of claims 1 to 8.

10. An electronic device, characterized in that: include: The power supply as claimed in claim 9.

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