Power switching circuit

Abstract

The utility model discloses a power switching circuit, the power switching circuit includes for switching output switching unit, the switching unit includes: first diode group, the input end of first diode group is connected second input voltage, conducting circuit, conducting circuit with the output end of first diode group links to each other, the output end of conducting circuit is used for according to second input voltage output first output voltage, comparison circuit, comparison circuit input end connects first input voltage and second input voltage, and the output end connects conducting circuit to according to first input voltage and second input voltage conducting conducting circuit, first conversion unit, first conversion unit input end links with first input voltage, and the output end links with the output end of conducting circuit to according to first input voltage output first output voltage. The utility model has realized millisecond level's seamless switching of power supply, and effectively solved the instantaneous power failure problem caused by traditional relay switching.

Description

Technical Field

[0001] This utility model relates to the field of power supply technology, and in particular to power switching circuits. Background Technology

[0002] In modern power electronic systems, especially in inverters with black-start capability, it is often necessary to handle inputs from different types of power sources and switch between these inputs. For example, in some applications, high-voltage AC (e.g., 400VAC) and high-voltage DC (e.g., 1500VDC) inputs may coexist, and the control system must ensure that a stable power supply to the control circuitry can be established and maintained when either input power source is present.

[0003] Traditional power switching solutions typically rely on relays. However, relays generally suffer from long operating times (usually greater than 20ms). Under heavy loads, this prolonged switching time can lead to momentary power outages or voltage drops at the output, affecting the stability and reliability of the entire system. To compensate for this deficiency, designers are often forced to increase the capacitance of the output support capacitor. However, this not only increases circuit board space and material costs but also fails to fundamentally solve the transient problems during switching. Furthermore, in high-voltage DC applications, relay contacts are prone to arcing during switching, further reducing reliability.

[0004] Therefore, the industry urgently needs a power supply circuit that can achieve fast and seamless switching to overcome the limitations of existing technologies. Utility Model Content

[0005] This invention aims to solve the problems of slow relay switching speed, instantaneous power outage, high requirements for supporting capacitor capacity, and risk of electric arc in existing power switching schemes, and provides a power switching circuit with a seamless switching function.

[0006] This utility model discloses a power switching circuit, which is used to output a first output voltage according to a first input voltage and / or a second input voltage. The power switching circuit includes a switching unit for switching the output, the switching unit comprising: A first diode group, the input terminal of the first diode group is connected to a second input voltage; A conducting circuit is connected to the output terminal of the first diode group, and the output terminal of the conducting circuit is used to output a first output voltage according to the second input voltage; A comparator circuit has an input terminal connected to a first input voltage and a second input voltage, and an output terminal connected to a conduction circuit to activate the conduction circuit according to the first input voltage and the second input voltage. The first conversion unit has its input terminal connected to the first input voltage and its output terminal connected to the output terminal of the conduction circuit to output a first output voltage according to the first input voltage.

[0007] In one or more embodiments of this utility model, the first diode group includes four groups of diodes connected in parallel. The input terminal of the first diode group is connected to a first connector. The first pin of the first connector is connected to a first input voltage, the second and third pins are grounded, and the fourth pin is connected to the first diode group and the second input voltage, respectively.

[0008] In one or more embodiments of this utility model, the conducting circuit includes a first MOSFET, a second MOSFET, a third MOSFET, a fourth MOSFET, a third Zener diode, a fourth Zener diode, a fifth Zener diode, and a sixth Zener diode, wherein, The source of the first MOSFET is connected to the output of the first diode group, the drain outputs the first output voltage, and the gate is connected to the source through the third Zener diode. The gate of the first MOSFET is also connected to the output of the comparator circuit. The source of the second MOSFET is connected to the gate of the first MOSFET, the drain of the second MOSFET is connected to the drain of the first MOSFET, the gate of the second MOSFET is connected to the gate of the first MOSFET, the gate of the second MOSFET is also connected to the source of the second MOSFET through a fourth Zener diode, and the gate of the second MOSFET is also connected to the output terminal of the comparator circuit. The source of the third MOS transistor is connected to the gate of the second MOS transistor, the drain of the third MOS transistor is connected to the drain of the first MOS transistor, the gate of the third MOS transistor is connected to the gate of the second MOS transistor, the gate of the third MOS transistor is also connected to the source of the third MOS transistor through the fifth Zener diode, and the gate of the third MOS transistor is connected to the output terminal of the comparator circuit. The gate of the fourth MOS transistor is connected to the source of the fourth MOS transistor through the sixth Zener diode, the source of the fourth MOS transistor is connected to the source of the first MOS transistor, the drain of the fourth MOS transistor is connected to the drain of the first MOS transistor, and the gate of the fourth MOS transistor is connected to the output terminal of the comparator circuit.

[0009] In one or more embodiments of this utility model, the comparison circuit includes a comparator, the first input terminal of the comparator is connected to a first input voltage through a fourteenth resistor, the second input terminal is connected to a second input voltage through a fifteenth resistor, and the output terminal is connected to the gate of a fourth MOS transistor.

[0010] In one or more embodiments of this utility model, the switching unit further includes a voltage divider circuit disposed between the fifteenth resistor and the second input voltage. The voltage divider circuit includes a sixteenth resistor, a seventeenth resistor, and a second Zener diode. The first terminal of the sixteenth resistor is connected to the second input voltage, the second terminal is connected to the first terminal of the seventeenth resistor, the second terminal of the seventeenth resistor is grounded, the second Zener diode is connected in parallel with the seventeenth resistor, the first terminal of the fifteenth resistor is connected to the second terminal of the sixteenth resistor, and the second terminal of the fifteenth resistor is connected to the second input terminal of the comparator.

[0011] In one or more embodiments of this utility model, the switching unit further includes a pull-up circuit, which includes a thirteenth resistor and an eighteenth resistor connected in parallel. The first end of the thirteenth resistor is connected to the second input voltage, and the second end of the thirteenth resistor is connected to the output of the comparator.

[0012] In one or more embodiments of this utility model, the switching unit further includes a pull-down circuit, which includes a nineteenth resistor and a twentieth resistor connected in parallel. The first end of the nineteenth resistor is connected to the output terminal of the comparator, and the second end is connected to the gate of the fourth MOS transistor.

[0013] In one or more embodiments of the present invention, the first conversion unit includes a second diode group, a supporting capacitor group, and a first conversion chip. The input terminal of the first conversion unit is connected to a first input voltage, the output terminal of the first conversion unit outputs a first output voltage through the supporting capacitor group, and the first conversion chip is connected to the supporting capacitor group.

[0014] In one or more embodiments of the present invention, the power switching circuit further includes a second conversion unit, the second conversion unit including a second conversion chip, and the input terminal of the second conversion chip being connected to the first output voltage.

[0015] In one or more embodiments of the present invention, the power switching circuit further includes an isolation unit connected to the first output voltage.

[0016] The beneficial effects of this utility model are: This invention enables seamless and rapid switching of the input power supply, with a switching time of less than 1ms, which is far lower than the typical switching time of a relay, effectively avoiding fluctuations in output voltage and momentary power outages during the switching process.

[0017] In this invention, the entire switching mechanism is implemented by a pure hardware circuit, which is simple in structure, fast in response, highly reliable, and avoids relay contact wear and arcing problems.

[0018] The switching circuit of this invention can completely cut off one power source from the other when switching between two input power sources through control logic, thereby improving the safety of system operation.

[0019] This invention has low requirements for the supporting capacitor capacity of the back-end load, and does not require excessive addition of capacitors to make up for the energy gap during switching, thereby effectively reducing the size of the circuit board and the overall cost. Attached Figure Description

[0020] Figure 1 This is a circuit diagram of the switching unit in one embodiment of the present invention; Figure 2 This is a circuit diagram of the first conversion unit in one embodiment of the present invention; Figure 3 This is a circuit diagram of the second conversion unit in one embodiment of the present invention; Figure 4 This is a circuit diagram of the isolation unit in one embodiment of the present invention; Figure 5 This is a circuit diagram of the display unit in one embodiment of the present invention.

[0021] In the figure: switching unit 100, first diode group 101, voltage divider circuit 102, comparator circuit 103, conduction circuit 104, pull-up circuit 105, pull-down circuit 106, first conversion unit 200, second diode group 201, supporting capacitor group 202, second conversion unit 300, isolation unit 400, display unit 500. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions of this utility model, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of this utility model.

[0023] In the description of this utility model, it should be understood that the terms "vertical", "horizontal", "top", "bottom", "upper", "lower", "front", "rear", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0024] It should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0025] like Figures 1-5 As shown, the power switching circuit provided by this utility model includes a switching unit 100 and a first conversion unit 200, which together constitute the core functional module for outputting a first output voltage VCC_24VIN1 according to the input voltage. In some embodiments, the power switching circuit may also selectively include a second conversion unit 300 and an isolation unit 400 to expand functionality or enhance performance.

[0026] In this embodiment, as Figure 1 The switching unit 100 shown includes a first diode group 101, a voltage divider circuit 102, a comparator circuit 103, a conduction circuit 104, a pull-up circuit 105, and a pull-down circuit 106.

[0027] In a further embodiment, the power switching circuit is configured with a first connector X2, model TP508H-00-4P, which serves as an interface for external input voltage. The first pin of the first connector X2 is used to connect to the first input voltage VCC_24VIN; the second and third pins are connected to ground; and the fourth pin is used to introduce the second input voltage VCC_24VIN2 and is connected to the input terminal of the first diode group 101 inside the switching unit 100.

[0028] In a further embodiment, the first diode group 101 includes four groups of diodes connected in parallel, which can be regarded as a rectifier bridge or a multi-channel reverse connection protection diode combination, with its input terminal connected to the second input voltage from the fourth pin of the first connector. This diode group mainly serves to prevent reverse connection and provide isolation, ensuring that the second input voltage safely enters the conduction circuit 104 and preventing current backflow; in this embodiment, four groups of diodes D13~D16 are connected in parallel.

[0029] In a further embodiment, a voltage divider circuit 102 is disposed between the second input voltage and the second input terminal of the comparator circuit 103. It includes a sixteenth resistor R16, a seventeenth resistor R17, and a second Zener diode Z2. Specifically, the first terminal of the sixteenth resistor R16 is connected to the second input voltage VCC_24VIN2, and its second terminal is connected to the first terminal of the seventeenth resistor R17; the second terminal of the seventeenth resistor R17 is grounded; and the second Zener diode Z2 is connected in parallel with the seventeenth resistor R17. The first terminal of the fifteenth resistor R15 is connected to the second terminal of the sixteenth resistor R16, and its second terminal is connected to the second input terminal of comparator N1A in the comparator circuit 103. The function of the voltage divider circuit 102 is to appropriately step down and regulate the second input voltage, providing a stable reference voltage for comparison by the comparator circuit 103.

[0030] In a further embodiment, the comparator circuit 103 is the core of the power switching logic. It includes a comparator, e.g., N1A. The first input terminal of comparator N1A is connected to the first input voltage VCC_24VIN through the fourteenth resistor R14, and its second input terminal receives the second input voltage signal processed by the voltage divider circuit 102. The output terminal of comparator N1A is connected to the gate of the fourth MOSFET VT4 in the turn-on circuit 104, and is used to generate a control signal to turn on or off the turn-on circuit 104 based on the comparison result of the first and second input voltages.

[0031] In a further embodiment, the conduction circuit 104 is composed of four MOSFETs and Zener diodes connected in parallel to achieve conduction control of the second input voltage path. It includes a first MOSFET VT1, a second MOSFET VT2, a third MOSFET VT3, a fourth MOSFET VT4, and a third Zener diode Z3, a fourth Zener diode Z4, a fifth Zener diode Z5, and a sixth Zener diode Z6.

[0032] The source of the first MOSFET VT1 is connected to the output of the first diode group 101, and its drain serves as the output node of the first output voltage VCC_24VIN1. The gate is connected to the source through the third Zener diode Z3 to provide appropriate gate bias or protection. The gate of the first MOSFET VT1 is connected to the output of the comparator circuit 103 to receive control signals.

[0033] The source of the second MOSFET VT2 is connected to the gate of the first MOSFET, its drain is connected to the drain of the first MOSFET, and its gate is connected to the gate of the first MOSFET VT1. Its gate is also connected to the source of the second MOSFET VT2 through a fourth Zener diode. This cascaded or parallel connection, combined with the Zener diode, helps to achieve reliable driving and voltage clamping of multiple MOSFETs. The gate of the second MOSFET VT2 is connected to the output of the comparator circuit 103 to receive control signals.

[0034] The source of the third MOSFET VT3 is connected to the gate of the second MOSFET, its drain is connected to the drain of the first MOSFET VT1, and its gate is connected to the gate of the second MOSFET. Its gate is also connected to the source of the third MOSFET VT1 through the fifth Zener diode. This further improves the MOSFET driving and protection mechanism. The gate of the third MOSFET VT3 is connected to the output of the comparator circuit 103 to receive control signals.

[0035] The fourth MOSFET VT4 is a switching element directly controlled by the comparator circuit 103. Its source is connected to the source of the first MOSFET, and its drain is connected to the drain of the first MOSFET VT1. The gate of the fourth MOSFET VT4 is connected to the output of the comparator circuit 103 to receive the control signal. The gate is connected to the source through the sixth Zener diode Z6 to limit the gate-source voltage, prevent overvoltage damage, and ensure reliable turn-on or turn-off.

[0036] In a further embodiment, the pull-up circuit 105 includes a thirteenth resistor R13 and an eighteenth resistor R18 connected in parallel. The first terminal of the thirteenth resistor R13 is connected to the second input voltage VCC_24VIN2, and its second terminal is connected to the output of the comparator circuit 103. The pull-up circuit 105 provides a stable high level when the comparator output is in a high-impedance state or when a high level needs to be ensured, for example, when the comparator output is open-drain.

[0037] In a further embodiment, the pull-down circuit 106 includes a nineteenth resistor R19 and a twentieth resistor R20 connected in parallel. The first terminal of the nineteenth resistor R19 is connected to the output of the comparator circuit 103, and its second terminal is connected to the gate of the fourth MOSFET VT4. This circuit functions to ensure reliable turn-off of the MOSFET or a stable state under specific conditions when the comparator output needs to be pulled low or a specific bias is provided to the gate of the fourth MOSFET VT4.

[0038] like Figure 2As shown, in a further embodiment, the first conversion unit 200 is responsible for providing a stable output when the first input voltage is used as the main power supply. It includes a second diode group 201, a supporting capacitor group 202, and a first conversion chip. In this embodiment, the first conversion chip is model URA2415LD-60WR3, which is used to convert 24V voltage to 15V voltage. The input terminal of the first conversion unit 200 is connected to the first input voltage and includes the second diode group 201, the supporting capacitor group 202, and the first conversion chip. The first conversion chip converts the first input voltage into the required intermediate voltage, and performs rectification or reverse connection protection through the second diode group 201, followed by filtering and energy storage by the supporting capacitor group 202, finally outputting the first output voltage. Its output terminal is connected to the output terminal of the conduction circuit 104, forming a power supply path in parallel with the conduction circuit 104.

[0039] like Figure 3 As shown, the second conversion unit 300 may further include a second conversion chip. In this embodiment, the second conversion chip is model URB2405LD-20W35VR3, which is used to convert 24V voltage to 5V voltage. The isolation unit 400 is used to provide electrical isolation, improving the system's safety or EMC performance. The power switching circuit may further include the second conversion unit 300, which contains the second conversion chip. Its input terminal is connected to the first output voltage and can be used to provide voltage conversion for other paths. Figure 4 As shown, the isolation unit 400 is connected to the first output voltage VCC_24VIN1 to provide electrical isolation and enhance safety.

[0040] like Figure 5 As shown, in a further embodiment, a display unit 500 is also included, which consists of a resistor and an LED connected in series, for displaying the working status of the power module.

[0041] The power switching circuit of this invention can intelligently select the power supply path and achieve seamless switching based on the presence and level of the first and second input voltages. Its main operating logic can be described through the following two scenarios: When the second input voltage VCC_24VIN2 is missing or inactive: When only the first input voltage VCC_24VIN is connected, and the second input voltage VCC_24VIN2 is missing (e.g., VCC_24VIN is 0V or lower than a preset threshold), the comparator circuit 103 will detect the low level of the second input voltage VCC_24VIN2 through the voltage divider circuit 102. At this time, the output terminal of comparator N1A will be in a floating state, and its output voltage will be 0V, causing the fourth MOSFET to turn on. However, because there is a first diode group 101 in the circuit, the path of the second input voltage VCC_24VIN2, which is composed of the first diode group 101 and the conduction circuit 104, is cut off, and no power is supplied to the output terminal. The first output voltage VCC_24VIN1 will not affect the second output voltage VCC_24VIN2.

[0042] Meanwhile, the first input voltage VCC_24VIN is filtered and regulated by the first conversion unit 200. The first conversion chip in the first conversion unit 200 converts the first input voltage VCC_24VIN into a stable first output voltage VCC_24VIN1, and smoothly outputs a 15V voltage through the supporting capacitor bank 202, thereby independently providing the first output voltage VCC_24VIN1 to the load from the first input voltage VCC_24VIN.

[0043] When the second input voltage VCC_24VIN2 is connected and in an active state: When the second input voltage VCC_24VIN2 is applied and reaches a preset activation level, for example, this voltage enters the first diode group 101 through the fourth pin of the first connector. At the same time, the voltage divider circuit 102 processes the second input voltage VCC_24VIN2 and sends it to the second input terminal of comparator N1A of the comparator circuit 103.

[0044] The comparator circuit 103 compares the first input voltage VCC_24VIN with the sampled value of the second input voltage VCC_24VIN2 from the voltage divider circuit 102 via the fourteenth resistor. The second input terminal of comparator N1A receives a 20V voltage sample, and the first input terminal of comparator N1A receives the first input voltage VCC_24VIN, which is 24V. The output pin of comparator N1A outputs a low level, at which point the gate voltage of the fourth MOSFET VT4 is 0V, and MOSFET VT4 is turned on.

[0045] When the fourth MOSFET VT4 is turned on, its control path will enable the circuit consisting of the first MOSFET, the second MOSFET, and the third MOSFET in the conduction circuit 104 to conduct. At this time, the second input voltage VCC_24VIN2 from the first diode group 101 will provide the first output voltage VCC_24VIN1 to the load via the conduction circuit 104.

[0046] During this process, since the second input voltage VCC_24VIN2 has taken over the power supply, the voltages across the second diode group 201 are equal. The first conversion unit 200 stops supplying power to the output terminal, and the conduction circuit 104 prioritizes power supply. The entire switching process, thanks to the use of fast-response MOSFETs and comparators, has an extremely short switching time, ensuring that the output voltage does not fluctuate significantly when the second input voltage takes over the power supply, achieving "bump-free switching." Furthermore, when the second input voltage VCC_24VIN2 completely takes over the power supply, the first diode group 101 can effectively prevent current from flowing back to the first input voltage VCC_24VIN1 side.

[0047] When the second input voltage VCC_24VIN2 is deactivated: When the second input voltage VCC_24VIN2 is unexpectedly disconnected or actively shut down, the comparator circuit 103 will quickly detect the voltage drop or disappearance at the second input voltage terminal. During this switching process, the sixth Zener diode Z6 is connected between the source and gate of the fourth MOSFET VT4 in the conduction circuit 104. When the second input voltage VCC_24VIN2 is disconnected, causing the output voltage VCC_24VIN1 to start to drop, the Zener diode can quickly clamp the gate-source voltage difference of the P-channel MOSFET, ensuring that the MOSFET reliably and quickly enters the turn-off state. This allows the first conversion unit 200 to immediately and seamlessly restore power supply to the output terminal, with the first input voltage VCC_24VIN providing a stable first output voltage VCC_24VIN1.

[0048] In this embodiment, since the first conversion unit 200 is always connected to the first input voltage and is in standby mode, once the conduction circuit 104 is turned off, the first conversion unit 200 will immediately restore power supply to the output terminal, and the first output voltage will be provided by the first input voltage again. The entire switching process is also fast and smooth, ensuring the continuity of the output power supply and avoiding power failure of the downstream load. The Zener diodes between the gate and source of the MOS transistor in the conduction circuit 104, such as the third Zener diode Z3, the fourth Zener diode Z4, the fifth Zener diode Z5, and the sixth Zener diode Z6, help to keep the gate-source voltage within a safe range when the voltage changes rapidly, preventing the MOS transistor from being mis-conducted or damaged. In this embodiment, four PMOS transistors are used in parallel, and the gates of the four MOS transistors are all connected to the output terminal of the comparator N1A to receive the control signal of the comparator. The parallel connection of the four MOS transistors can increase the circuit current and prevent the MOS transistors from being burned out. In specific implementations, the number of MOS transistors connected in parallel can be adjusted according to actual needs.

[0049] The power switching circuit of this invention can achieve high-speed, seamless switching between dual input power supplies, significantly improving the reliability and stability of power supply, and effectively reducing the requirements for external support capacitor capacity. It has broad application prospects in systems with complex power switching requirements.

[0050] The above embodiments are only for illustrating the technical concept and features of this utility model. Their purpose is to enable those skilled in the art to understand the content of this utility model and implement it. They cannot be used to limit the protection scope of this utility model. All equivalent changes or modifications made in accordance with the spirit and essence of this utility model should be covered within the protection scope of this utility model.

Claims

1. A power switching circuit, the power switching circuit being used to output a first output voltage according to a first input voltage and / or a second input voltage, characterized in that, The power switching circuit includes a switching unit (100) for switching outputs, the switching unit (100) comprising: The first diode group (101) has its input terminal connected to the second input voltage; A conducting circuit (104) is connected to the output terminal of the first diode group (101), and the output terminal of the conducting circuit (104) is used to output a first output voltage according to the second input voltage; A comparator circuit (103) has an input terminal connected to a first input voltage and a second input voltage, and an output terminal connected to a conduction circuit (104) to conduct the conduction circuit (104) according to the first input voltage and the second input voltage. The first conversion unit (200) has its input terminal connected to the first input voltage and its output terminal connected to the output terminal of the conduction circuit (104) to output a first output voltage according to the first input voltage.

2. The power switching circuit according to claim 1, characterized in that, The first diode group (101) includes four groups of diodes connected in parallel. The input terminal of the first diode group (101) is connected to the first connector. The first pin of the first connector is connected to the first input voltage, the second pin and the third pin are grounded, and the fourth pin is connected to the first diode group (101) and the second input voltage, respectively.

3. A power switching circuit according to claim 2, characterized in that, The conducting circuit (104) includes a first MOSFET, a second MOSFET, a third MOSFET, a fourth MOSFET, a third Zener diode, a fourth Zener diode, a fifth Zener diode, and a sixth Zener diode, wherein... The source of the first MOS transistor is connected to the output terminal of the first diode group (101), the drain outputs the first output voltage, and the gate is connected to the source through the third Zener diode. The gate of the first MOS transistor is also connected to the output terminal of the comparator circuit (103). The source of the second MOSFET is connected to the gate of the first MOSFET, the drain of the second MOSFET is connected to the drain of the first MOSFET, the gate of the second MOSFET is connected to the gate of the first MOSFET, the gate of the second MOSFET is also connected to the source of the second MOSFET through the fourth Zener diode, and the gate of the second MOSFET is also connected to the output terminal of the comparator circuit (103). The source of the third MOS transistor is connected to the gate of the second MOS transistor, the drain of the third MOS transistor is connected to the drain of the first MOS transistor, the gate of the third MOS transistor is connected to the gate of the second MOS transistor, the gate of the third MOS transistor is also connected to the source of the third MOS transistor through the fifth Zener diode, and the gate of the third MOS transistor is connected to the output terminal of the comparator circuit (103). The gate of the fourth MOS transistor is connected to the source of the fourth MOS transistor through the sixth Zener diode, the source of the fourth MOS transistor is connected to the source of the first MOS transistor, the drain of the fourth MOS transistor is connected to the drain of the first MOS transistor, and the gate of the fourth MOS transistor is connected to the output terminal of the comparator circuit (103).

4. A power switching circuit according to claim 3, characterized in that, The comparator circuit (103) includes a comparator, the first input terminal of which is connected to the first input voltage through the fourteenth resistor, the second input terminal of which is connected to the second input voltage through the fifteenth resistor, and the output terminal of which is connected to the gate of the fourth MOS transistor.

5. A power switching circuit according to claim 4, characterized in that, The switching unit (100) further includes a voltage divider circuit (102) disposed between the fifteenth resistor and the second input voltage. The voltage divider circuit (102) includes a sixteenth resistor, a seventeenth resistor and a second Zener diode. The first end of the sixteenth resistor is connected to the second input voltage, the second end is connected to the first end of the seventeenth resistor, the second end of the seventeenth resistor is grounded, the second Zener diode is connected in parallel with the seventeenth resistor, the first end of the fifteenth resistor is connected to the second end of the sixteenth resistor, and the second end of the fifteenth resistor is connected to the second input terminal of the comparator.

6. A power switching circuit according to claim 4, characterized in that, The switching unit (100) further includes a pull-up circuit (105), which includes a thirteenth resistor and an eighteenth resistor connected in parallel. The first end of the thirteenth resistor is connected to the second input voltage, and the second end of the thirteenth resistor is connected to the output of the comparator.

7. A power switching circuit according to claim 4, characterized in that, The switching unit (100) further includes a pull-down circuit (106), which includes a nineteenth resistor and a twentieth resistor connected in parallel. The first end of the nineteenth resistor is connected to the output of the comparator, and the second end is connected to the gate of the fourth MOS transistor.

8. A power switching circuit according to claim 1, characterized in that, The first conversion unit (200) includes a second diode group (201), a supporting capacitor group (202), and a first conversion chip. The input terminal of the first conversion unit (200) is connected to a first input voltage, and the output terminal of the first conversion unit (200) is connected to the first output voltage through the output terminal of the supporting capacitor group (202). The first conversion chip is connected to the supporting capacitor group (202).

9. A power switching circuit according to claim 1, characterized in that, The power switching circuit further includes a second conversion unit (300), which includes a second conversion chip, the input terminal of which is connected to the first output voltage.

10. A power switching circuit according to claim 1, characterized in that, The power switching circuit also includes an isolation unit (400) connected to the first output voltage.

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