Anti-backflow MOS switching circuit

Abstract

The invention discloses an anti-backflow MOS switching circuit, which comprises an MOS tube, an anti-backflow voltage comparison circuit, a switching circuit, a filtering voltage stabilizing circuit and a protection circuit, and is characterized in that a source electrode of the MOS tube is jointly connected with a second input end of the anti-backflow voltage comparison circuit, a second input end of the switching circuit, a second input end of the filtering voltage stabilizing circuit and a first input end of the protection circuit; the drain electrode of the MOS tube is jointly connected with the first input end of the anti-backflow voltage comparison circuit and the second input end of the protection circuit, and the grid electrode of the MOS tube is jointly connected with the first output end of the filtering voltage stabilizing circuit and the first output end of the protection circuit; the first output end of the anti-backflow voltage comparison circuit is connected with the first input end of the switching circuit; the driving voltage is connected with the third input end of the anti-backflow voltage comparison circuit, the third input end of the filtering voltage stabilizing circuit and the third input end of the protection circuit. According to the invention, damage to internal components of the circuit caused by current or voltage backflow can be effectively prevented.

Description

Technical Field

[0001] The invention relates to the technical field of switching power supplies, and in particular to an anti-backflow MOS switching circuit. Background Art

[0002] A switching power supply is a high-efficiency power supply device that uses modern power electronics technology. Its core lies in ensuring the stability and accuracy of the output voltage by regulating the ratio of the on and off time of switching elements (such as transistors). Compared with traditional linear power supplies, switching power supplies have more compact size, higher energy conversion efficiency and greater power output capacity. These advantages make them the preferred power supply solution in many fields such as automobiles, photovoltaic energy, industrial automation control, medical equipment and portable electronic devices. With the continuous advancement and innovation of technology, switching power supplies are moving towards higher frequency, higher power density and smaller size. In this process, high-performance power semiconductor devices such as MOSFET (metal oxide semiconductor field effect transistor) and IGBT (insulated gate bipolar transistor) are widely used in the power level of switching power supplies as key switching components due to their superior performance under high frequency conditions. Its stable and reliable operation is inseparable from the high-precision switching circuit. The specific position of the power switch tube in various topological architectures not only affects the performance of the power supply, but also directly determines the design and implementation of the switching circuit.

[0003] The anti-backflow circuit occupies a pivotal position in the switching power supply system. Its core design is to prevent the current from flowing in reverse when the power fails or the equipment is shut down and the load presents capacitive characteristics, thereby effectively protecting the circuit components from damage. When constructing such circuits, the optimized design of the switching circuit is particularly critical. It requires the power switching device to respond to control instructions quickly and accurately, while ensuring reliable electrical isolation from the main circuit, so as to completely eliminate potential safety threats. The existing anti-backflow MOS tube still has some shortcomings. The stability and accuracy of the MOS tube gate voltage are crucial to its conduction state. However, in actual applications, in the face of certain extreme environments, the gate voltage may be affected by factors such as power supply voltage fluctuations and load changes, resulting in the MOS tube being unable to be fully turned on or off, resulting in a decrease in circuit performance and even causing failures.

[0004] In order to ensure that the circuit can maintain high stability in various complex and changeable operating environments and ensure its safe operation, it is particularly important to design and add an anti-backflow MOS switch circuit. The performance of the MOS switch circuit is directly related to the effectiveness of the anti-backflow protection mechanism, which has an important impact on the reliability and stability of the entire power supply system. Therefore, it is urgent to develop a new type of anti-backflow MOS switch circuit to meet the strict requirements of the switching power supply industry for high performance, high reliability and high safety. Summary of the invention

[0005] In view of this, the present invention aims to provide an anti-backflow MOS switch circuit to solve the technical problem of circuit performance degradation caused by the inability of the MOS tube to be completely turned on or off under extreme environments.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: A backflow prevention MOS switch circuit includes a MOS tube, a backflow prevention voltage comparison circuit, a switch circuit, a filter voltage stabilization circuit and a protection circuit, wherein: The source of the MOS tube is commonly connected to the second input end of the anti-backflow voltage comparison circuit, the second input end of the switch circuit, the second input end of the filter voltage stabilization circuit, and the first input end of the protection circuit; the drain of the MOS tube is commonly connected to the first input end of the anti-backflow voltage comparison circuit and the second input end of the protection circuit, and the gate of the MOS tube is commonly connected to the first output end of the filter voltage stabilization circuit and the first output end of the protection circuit; the first output end of the anti-backflow voltage comparison circuit is connected to the first input end of the switch circuit; the driving voltage VDD IsoMOS is respectively connected to the third input end of the anti-backflow voltage comparison circuit, the third input end of the filter voltage stabilization circuit, and the third input end of the protection circuit; the first output end of the switch circuit is connected to the first input end of the filter voltage stabilization circuit.

[0007] Furthermore, the anti-backflow voltage comparison circuit includes a transistor Q1, a transistor Q2, a resistor R29, a resistor R30 and a resistor R38; wherein the emitter of the transistor Q1 is connected to the base of the transistor Q1, the base of the transistor Q2 and one end of the resistor R29; the collector of the transistor Q2 is connected to one end of the resistor R30, and the end point of the connection is connected to the first input end of the switching circuit as the first output end of the anti-backflow voltage comparison circuit; the other end of the resistor R29 is connected to the other end of the resistor R30, and the end point of the connection is connected to the driving voltage VDD as the third input end of the anti-backflow voltage comparison circuit, the third input end of the filtering and voltage stabilization circuit, and the third input end of the protection circuit. IsoMOS; the emitter of the transistor Q2 is connected to one end of the resistor R38; the collector of the transistor Q1 is connected to the drain of the MOS tube as the first input end of the anti-backflow voltage comparison circuit; the other end of the resistor R38 is used as the second input end of the anti-backflow voltage comparison circuit, and is connected to the source of the MOS tube, the second input end of the switch circuit, the second input end of the filter and voltage stabilization circuit, and the first input end of the protection circuit.

[0008] Furthermore, the switching circuit includes a diode D7 and a transistor Q15; wherein the anode of the diode D7 is connected to the base of the transistor Q15, and the end point of the connection is connected to the first output end of the anti-backflow voltage comparison circuit as the first input end of the switching circuit 3; the cathode of the diode D7 is connected to the emitter of the transistor Q15, and the end point of the connection is connected to the first input end of the filter voltage stabilization circuit as the first output end of the switching circuit; the collector of the transistor Q15 is connected to the source of the MOS tube, the second input end of the anti-backflow voltage comparison circuit, the second input end of the filter voltage stabilization circuit, and the first input end of the protection circuit as the second input end of the switching circuit.

[0009] Furthermore, the filtering and voltage-stabilizing circuit includes a diode D8, a voltage-stabilizing diode D9, a resistor R31 and a capacitor C7; wherein, the anode of the diode D8 is connected to one end of the resistor R31, and the end point of the connection is connected to the first output end of the switching circuit as the first input end of the filtering and voltage-stabilizing circuit; the other end of the resistor R31 is connected to the gate of the MOS tube as the first output end of the filtering and voltage-stabilizing circuit; the cathode of the diode D8 is connected to the cathode of the voltage-stabilizing diode D9; the anode of the voltage-stabilizing diode D9 is connected to one end of the capacitor C7, and the end point of the connection is connected to the second input end of the filtering and voltage-stabilizing circuit, and is commonly connected to the source of the MOS tube, the second input end of the anti-backflow voltage comparison circuit, the second input end of the switching circuit, and the first input end of the protection circuit; the other end of the capacitor C7 is connected to the third input end of the filtering and voltage-stabilizing circuit, and is commonly connected to the driving voltage VDD IsoMOS with the third input end of the anti-backflow voltage comparison circuit and the third input end of the protection circuit.

[0010] Furthermore, the protection circuit includes a voltage comparator U1 and a transistor Q16; wherein, pin 1 of the voltage comparator U1 is connected to the base of the transistor Q16, and pin 2 of the voltage comparator U1 is connected as the power input end of the voltage comparator and is connected to the driving voltage VDD IsoMOS together with the third input end of the filter voltage stabilization circuit and the third input end of the anti-backflow voltage comparison circuit; the pin of the voltage comparator U1 is connected as the second input end of the protection circuit and is connected to the drain of the MOS tube and the first input end of the anti-backflow voltage comparison circuit; pin 4 of the voltage comparator U1 is connected as the first input end of the protection circuit and is connected to the source of the MOS, the second input end of the anti-backflow voltage comparison circuit, the second input end of the switch circuit, and the second input end of the filter voltage stabilization circuit; pin 5 of the comparator U1 and the emitter of the transistor Q16 are connected to the source of the MOS tube, and the collector of the transistor Q16 is connected as the first output end of the protection circuit and is connected to the gate of the MOS tube and the first output end of the filter voltage stabilization circuit.

[0011] Compared with the prior art, the present invention has the following beneficial effects: The present invention integrates a switch circuit at both ends of the MOS tube to detect the voltage change at both ends of the MOS tube in real time, and determines whether to turn on the driving mechanism of the MOS tube based on the size of the detection voltage, thereby ensuring that the MOS tube can achieve efficient and accurate on-off control. When the drain voltage at the output end is higher than the source voltage at the input end, the switch circuit can control the conduction state of the diode and the transistor in the switch circuit according to the level of the sampling voltage, and then output an accurate drive voltage in the filter voltage stabilization circuit to transmit it to the MOS tube gate, thereby controlling the conduction state of the MOS tube. In summary, the present invention can effectively prevent the damage of internal components of the circuit caused by current or voltage backflow caused by excessive output capacitance, abnormal output or reverse output, significantly improve the reliability and stability of the circuit, and extend the service life of the electronic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a structural schematic diagram of the anti-backflow MOS switch circuit of the present invention; Figure 2 It is a circuit principle diagram of the anti-backflow MOS switch circuit of the present invention; The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. DETAILED DESCRIPTION

[0013] like Figure 1 As shown, the anti-backflow MOS switch circuit provided by the present invention includes a MOS tube 1, an anti-backflow voltage comparison circuit 2, a switch circuit 3, a filter voltage stabilization circuit 4 and a protection circuit 5, wherein: The source of the MOS tube 1 is commonly connected to the second input end of the anti-backflow voltage comparison circuit 2, the second input end of the switch circuit 3, the second input end of the filter voltage stabilization circuit 4, and the first input end of the protection circuit 5; the drain of the MOS tube 1 is commonly connected to the first input end of the anti-backflow voltage comparison circuit 2 and the second input end of the protection circuit 5, and the gate of the MOS tube 1 is commonly connected to the first output end of the filter voltage stabilization circuit 4 and the first output end of the protection circuit 5; the first output end of the anti-backflow voltage comparison circuit 2 is connected to the first input end of the switch circuit 3; the driving voltage VDD IsoMOS is respectively connected to the third input end of the anti-backflow voltage comparison circuit 2, the third input end of the filter voltage stabilization circuit 4 and the third input end of the protection circuit 5; the first output end of the switch circuit 3 is connected to the first input end of the filter voltage stabilization circuit 4.

[0014] In the above technical solution, the functions of each part are as follows: The MOS tube 1 is used to prevent the backflow current generated when the power supply is reversely connected or the load is short-circuited from damaging the circuit used in the present invention; The anti-backflow voltage comparison circuit 2 is used to collect and compare the voltages at the source and drain of the MOS tube 1, and provide a trigger voltage for the switch circuit 3 according to the comparison result; The switch circuit 3 is used to compare the voltage input from the anti-backflow voltage comparison circuit 2 (i.e., the voltage from the first output terminal of the anti-backflow voltage comparison circuit 2 to the first input terminal of the switch circuit 3), and output high and low level signals to the filter voltage stabilization circuit 4; The filtering and stabilizing circuit 4 is used to filter and stabilize the high and low level signals output by the switching circuit 3 (i.e., from the first output end of the switching circuit 3 to the first input end of the filtering and stabilizing circuit 4), and then provide a stable driving voltage for the gate of the MOS tube 1.

[0015] The protection circuit 5 is used to quickly lower the gate voltage of the MOS tube 1 when V2 is greater than V1 to prevent the backflow current from damaging the circuit used in the present invention. The protection circuit 5 provides protection for the drive circuit composed of the anti-backflow voltage comparison circuit 2, the switch circuit 3 and the filter voltage regulator circuit 4.

[0016] VDD IsoMOS provides stable power supply for the anti-backflow voltage comparison circuit 2, the filtering and voltage stabilizing circuit 4 and the protection circuit 5, and provides a stable input voltage for the three circuits as a whole.

[0017] like Figure 2 As shown, the circuit design of this embodiment is as follows: The anti-backflow voltage comparison circuit 2 includes a transistor Q1, a transistor Q2, a resistor R29, a resistor R30 and a resistor R38; wherein the emitter of the transistor Q1 is connected to the base of the transistor Q1, the base of the transistor Q2 and one end of the resistor R29; the collector of the transistor Q2 is connected to one end of the resistor R30, and the end point of the connection is connected to the first input end of the switch circuit 3 as the first output end of the anti-backflow voltage comparison circuit 2; the other end of the resistor R29 is connected to the other end of the resistor R30, and the end point of the connection is connected to the driving voltage VDD as the third input end of the anti-backflow voltage comparison circuit 2, the third input end of the filter voltage stabilization circuit 4, and the third input end of the protection circuit 5. IsoMOS; the emitter of transistor Q2 is connected to one end of resistor R38; the collector of transistor Q1 is connected to the drain of MOS tube 1 as the first input end of anti-backflow voltage comparison circuit 2; the other end of resistor R38 is connected to the source of MOS tube 1, the second input end of switch circuit 3, the second input end of filter voltage regulator circuit 4 and the first input end of protection circuit 5 as the second input end of anti-backflow voltage comparison circuit 2; The switch circuit 3 includes a diode D7 and a transistor Q15; wherein the anode of the diode D7 is connected to the base of the transistor Q15, and the end point of the connection is connected to the first output end of the anti-backflow voltage comparison circuit 2 as the first input end of the switch circuit 3; the cathode of the diode D7 is connected to the emitter of the transistor Q15, and the end point of the connection is connected to the first input end of the filter voltage stabilization circuit 4 as the first output end of the switch circuit 3; the collector of the transistor Q15 is connected to the source of the MOS tube 1, the second input end of the anti-backflow voltage comparison circuit 2, the second input end of the filter voltage stabilization circuit 4, and the first input end of the protection circuit 5 as the second input end of the switch circuit 3.

[0018] The filtering and voltage-stabilizing circuit 4 includes a diode D8, a voltage-stabilizing diode D9, a resistor R31 and a capacitor C7; wherein the anode of the diode D8 is connected to one end of the resistor R31, and the end point of the connection is connected to the first output end of the switch circuit 3 as the first input end of the filtering and voltage-stabilizing circuit 4; the other end of the resistor R31 is connected to the gate of the MOS tube 1 as the first output end (DRV IsoMOS) of the filtering and voltage-stabilizing circuit 4; the cathode of the diode D8 is connected to the cathode of the voltage-stabilizing diode D9; the anode of the voltage-stabilizing diode D9 is connected to one end of the capacitor C7, and the end point of the connection is connected to the source of the MOS tube 1, the second input end of the anti-backflow voltage comparison circuit 2, the second input end of the switch circuit 3, and the first input end of the protection circuit 5 as the second input end of the filtering and voltage-stabilizing circuit 4; the other end of the capacitor C7 is connected to the driving voltage VDD IsoMOS as the third input end of the filtering and voltage-stabilizing circuit 4, the third input end of the anti-backflow voltage comparison circuit 2, and the third input end of the protection circuit 5.

[0019] The protection circuit 5 includes a voltage comparator U1 and a transistor Q16; wherein, pin 1 of the voltage comparator U1 is connected to the base of the transistor Q16, and pin 2 of the voltage comparator U1 is connected to the driving voltage VDD IsoMOS as the power input end of the voltage comparator and the third input end of the filter voltage regulator circuit 4 and the third input end of the anti-backflow voltage comparison circuit 2; pin 3 of the voltage comparator U1 is connected to the drain of the MOS tube 1 and the first input end of the anti-backflow voltage comparison circuit 2 as the second input end of the protection circuit 5; pin 4 of the voltage comparator U1 is connected to the source of the MOS tube 1, the second input end of the anti-backflow voltage comparison circuit 2, the second input end of the switch circuit 3, and the second input end of the filter voltage regulator circuit 4 as the first input end of the protection circuit 5; pin 5 of the comparator U1 and the emitter of the transistor Q16 are connected to the source of the MOS tube 1, and the collector of the transistor Q16 is connected to the gate of the MOS tube 1 and the first output end of the filter voltage regulator circuit 4 as the first output end of the protection circuit 5.

[0020] In this embodiment, the selection of components is as follows: Transistor Q1 and transistor Q2 can be integrated components such as MMDT5551, or two discrete transistor components with the same PN junction characteristics can be integrated into one component; The value of resistor R29 is 5~20kΩ; The value of resistor R30 is 7~20kΩ; The value of resistor R38 is 33Ω; Diode D7 and diode D8 are Schottky diodes or fast recovery diodes, both of which are BAS516; The model of transistor Q15 is MMBT4403; The value of resistor R31 is 0.1Ω; Diode D9 is a voltage regulator diode, model BZX585_B13; The model of capacitor C7 is 1uF; The model of transistor Q16 can be the same as that of transistor Q1 and transistor Q2, which is MMBT5551; The model of voltage comparator U1 is LMV7219M5 / TR.

[0021] The working principle of the present invention is as follows: When the present invention is used, the MOS tube 1 is connected to the circuit used by the present invention. In actual application, the flow direction of the current in the circuit is connected to the source and drain of the MOS tube 1 in sequence.

[0022] like Figure 2 As shown, the input voltage V1 and the output voltage V2 at both ends of the MOS tube 1 are detected by the anti-backflow voltage comparison circuit 2. When the input voltage V1 is greater than the output voltage V2, at this time, since the emitter of the first terminal of the transistor Q1 is connected to the base of the second terminal, the transistor Q1 cannot obtain sufficient bias voltage and remains in the cut-off state, and its emitter is connected to the base of the transistor Q2. Since the base voltage of the transistor Q2 is lower than the emitter voltage, the transistor Q2 cannot be turned on either. In this state, the current provided by the driving voltage VDD IsoMOS connected to the anti-backflow voltage comparison circuit 2 will flow through the resistor R30 and the diode D7 in the switch circuit 3 in turn, and continue to flow into the filter voltage stabilizing circuit 4. Through the combined action of the diode D8 and the voltage stabilizing diode D9, the output voltage is stably controlled between 10V and 15V, and flows out from the DRV IsoMOS as a high-level signal to provide the necessary power supply voltage for the gate of the MOS tube 1. At this time, the protection circuit does not act, thereby ensuring its normal conduction.

[0023] When the input voltage V1 is less than the output voltage V2, the connection state of the integrated components of transistors Q1 and Q2 remains unchanged, and transistor Q1 is still cut off, but at this time, the base voltage of transistor Q2 is higher than its emitter voltage, so transistor Q2 starts to turn on. As a result, the current provided by VDD IsoMOS no longer flows to the filter voltage regulator circuit 4 after flowing through the resistor R30, but directly flows into the node where the input voltage V1 is located through the resistor R38. At this time, since the collector voltage of the third terminal of transistor Q2 is pulled down to V1, the transistor Q15 in the switch circuit 3 obtains sufficient bias voltage and turns on. Further, the output voltage is also pulled down to the V1 level, and a low-level signal is output. In this case, since the voltage difference between the source and the gate of the MOS tube 1 is not enough to reach its turn-on voltage, the MOS tube 1 will be turned off, and after the action of the voltage comparator U1, its output is high level, thereby causing the transistor Q16 to be turned on, and the DRV IsoMOS voltage is pulled down to V1, effectively preventing the reverse current from flowing into the switching power supply, thereby protecting the safe and stable operation of the entire circuit system.

[0024] Effects of the present invention: Generally, the switch circuits of anti-backflow MOS are relatively simple and not very stable, especially under certain extreme conditions, the problem of backflow current may still occur. The anti-backflow MOS switch circuit of the present invention has low power consumption characteristics when working, ensuring that the circuit can maintain efficient utilization during continuous operation. Secondly, the circuit has excellent rapid response capability and can quickly capture the changes between the output voltage V2 and the input voltage V1. When the output voltage V2 is greater than the input voltage V1, the anti-backflow MOS switch circuit of the present invention can quickly detect the changes and output the appropriate driving voltage in time, thereby effectively driving the MOS tube to perform a shutdown operation, preventing the generation of backflow current, and protecting the safe and stable operation of the entire circuit system.

[0025] As shown above, the technical effects of the present invention are as follows: (1) The switch circuits of general anti-backflow MOS are relatively simple and have low stability. In particular, under certain extreme conditions, the problem of backflow current may still occur. The anti-backflow MOS switch circuit of the present invention has low power consumption characteristics when working, ensuring that the circuit can maintain high efficiency during continuous operation.

[0026] (2) Secondly, the circuit of the present invention has excellent rapid response capability and can quickly capture the change between the output voltage V2 and the input voltage V1. When the output voltage V2 is greater than the input voltage V1, the switch circuit 3 can quickly detect the change and output a suitable driving voltage in time, thereby effectively driving the MOS tube to perform a shutdown operation, preventing the generation of backflow current, and protecting the safe and stable operation of the entire circuit system.

[0027] The above are only preferred embodiments of the present invention. It should be pointed out that the above preferred embodiments should not be regarded as limitations of the present invention. For ordinary technicians in this technical field, several improvements can be made without departing from the scope of the present invention. Without departing from the purpose and scope of the technical solution of the patent of the present invention, they should all be covered in the scope of the claims of the patent of the present invention.

Claims

1. A backflow prevention MOS switch circuit, characterized in that: It comprises a MOS tube (1), an anti-backflow voltage comparison circuit (2), a switch circuit (3), a filter voltage regulator circuit (4) and a protection circuit (5), wherein: The source of the MOS tube (1) is commonly connected to the second input end of the anti-backflow voltage comparison circuit (2), the second input end of the switch circuit (3), the second input end of the filter voltage stabilization circuit (4), and the first input end of the protection circuit (5); the drain of the MOS tube (1) is commonly connected to the first input end of the anti-backflow voltage comparison circuit (2) and the second input end of the protection circuit (5); the gate of the MOS tube (1) is commonly connected to the first output end of the filter voltage stabilization circuit (4) and the first output end of the protection circuit (5); the first output end of the anti-backflow voltage comparison circuit (2) is connected to the first input end of the switch circuit (3); the driving voltage VDD IsoMOS is respectively connected to the third input end of the anti-backflow voltage comparison circuit (2), the third input end of the filter voltage stabilization circuit (4), and the third input end of the protection circuit (5); the first output end of the switch circuit (3) is connected to the first input end of the filter voltage stabilization circuit (4).

2. The anti-backflow MOS switch circuit according to claim 1, characterized in that: The anti-backflow voltage comparison circuit (2) comprises a transistor Q1, a transistor Q2, a resistor R29, a resistor R30 and a resistor R38; wherein the emitter of the transistor Q1 is connected to the base of the transistor Q1, the base of the transistor Q2 and one end of the resistor R29; the collector of the transistor Q2 is connected to one end of the resistor R30, and the end point of the connection is connected to the first input end of the switch circuit (3) as the first output end of the anti-backflow voltage comparison circuit (2); the other end of the resistor R29 is connected to the other end of the resistor R30, and the end point of the connection is connected to the third input end of the filter voltage stabilization circuit (4) and the third input end of the protection circuit (5) as the third input end of the anti-backflow voltage comparison circuit (2) and the driving voltage VDD. IsoMOS; the emitter of the transistor Q2 is connected to one end of a resistor R38; the collector of the transistor Q1 is connected to the drain of the MOS transistor (1) as the first input end of the anti-backflow voltage comparison circuit (2); the other end of the resistor R38 is connected to the source of the MOS transistor (1), the second input end of the switch circuit (3), the second input end of the filter voltage stabilization circuit (4) and the first input end of the protection circuit (5) as the second input end of the anti-backflow voltage comparison circuit (2).

3. The anti-backflow MOS switch circuit according to claim 2, characterized in that: The switch circuit (3) comprises a diode D7 and a transistor Q15; wherein the anode of the diode D7 is connected to the base of the transistor Q15, and the end point of the connection is connected to the first output end of the anti-backflow voltage comparison circuit (2) as the first input end of the switch circuit (3); the cathode of the diode D7 is connected to the emitter of the transistor Q15, and the end point of the connection is connected to the first input end of the filter voltage stabilization circuit (4) as the first output end of the switch circuit (3); the collector of the transistor Q15 is connected to the source of the MOS tube (1), the second input end of the anti-backflow voltage comparison circuit (2), the second input end of the filter voltage stabilization circuit (4), and the first input end of the protection circuit (5).

4. The anti-backflow MOS switch circuit according to claim 3, characterized in that: The filtering and voltage stabilizing circuit (4) comprises a diode D8, a voltage stabilizing diode D9, a resistor R31 and a capacitor C7; wherein the anode of the diode D8 is connected to one end of the resistor R31, and the end point of the connection is connected to the first output end of the switch circuit (3) as the first input end of the filtering and voltage stabilizing circuit (4); the other end of the resistor R31 is connected to the gate of the MOS tube (1) as the first output end of the filtering and voltage stabilizing circuit (4); the cathode of the diode D8 is connected to the cathode of the voltage stabilizing diode D9; the anode of the voltage stabilizing diode D9 is connected to one end of the capacitor C7, and the end point of the connection is connected to the second input end of the filtering and voltage stabilizing circuit (4), and is connected to the source of the MOS tube (1), the second input end of the anti-backflow voltage comparison circuit (2), the second input end of the switch circuit (3), and the first input end of the protection circuit (5); the other end of the capacitor C7 is connected to the third input end of the filtering and voltage stabilizing circuit (4), and is connected to the third input end of the anti-backflow voltage comparison circuit (2), and the third input end of the protection circuit (5) as the third input end of the filtering and voltage stabilizing circuit (4), and is connected to the driving voltage VDD IsoMOS.

5. The anti-backflow MOS switch circuit according to claim 4, characterized in that: The protection circuit (5) comprises a voltage comparator U1 and a transistor Q16; wherein pin 1 of the voltage comparator U1 is connected to the base of the transistor Q16, and pin 2 of the voltage comparator U1 is connected to the driving voltage VDD as the power input terminal of the voltage comparator and the third input terminal of the filter voltage stabilization circuit (4) and the third input terminal of the anti-backflow voltage comparison circuit (2). IsoMOS; Pin 3 of the voltage comparator U1 is connected as the second input end of the protection circuit (5) to the drain of the MOS tube (1) and the first input end of the anti-backflow voltage comparison circuit (2); Pin 4 of the voltage comparator U1 is connected as the first input end of the protection circuit (5) to the source of the MOS tube (1), the second input end of the anti-backflow voltage comparison circuit (2), the second input end of the switch circuit (3), and the second input end of the filter voltage stabilization circuit (4); Pin 5 of the comparator U1 is connected as the emitter of the transistor Q16 to the source of the MOS tube (1); and the collector of the transistor Q16 is connected as the first output end of the protection circuit (5) to the gate of the MOS tube (1) and the first output end of the filter voltage stabilization circuit (4).

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