An anti-backflow MOS switch circuit

Abstract

The present invention discloses an anti-backflow MOS switch circuit, which includes a MOS transistor, an anti-backflow voltage comparison circuit, a switch circuit, a filter voltage stabilization circuit and a protection circuit. The source electrode of the MOS transistor is commonly connected to the second input terminal of the anti-backflow voltage comparison circuit, the second input terminal of the switch circuit, the second input terminal of the filter voltage stabilization circuit and the first input terminal of the protection circuit; the drain electrode of the MOS transistor is commonly connected to the first input terminal of the anti-backflow voltage comparison circuit and the second input terminal of the protection circuit, and the gate electrode of the MOS transistor is commonly connected to the first output terminal of the filter voltage stabilization circuit and the first output terminal of the protection circuit; the first output terminal of the anti-backflow voltage comparison circuit is connected to the first input terminal of the switch circuit; the drive voltage is connected to the third input terminal of the anti-backflow voltage comparison circuit, the third input terminal of the filter voltage stabilization circuit and the third input terminal of the protection circuit. The present invention can effectively prevent the damage of internal circuit components caused by current or voltage backflow.

Description

Technical Field

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

[0002] A switching power supply is a high-efficiency power supply device that employs modern power electronics technology. Its core lies in regulating the on-off time ratio of switching elements (such as transistors) to ensure the stability and accuracy of the output voltage. Compared with traditional linear power supplies, switching power supplies exhibit a more compact volume, higher energy conversion efficiency, and greater power output capacity. These advantages make them the preferred power supply solutions in multiple fields such as automotive, photovoltaic energy, industrial automation control, medical equipment, and portable electronic devices. With the continuous progress and innovation of technology, switching power supplies are moving towards higher frequencies, higher power densities, and smaller volumes. In this process, high-performance power semiconductor devices such as MOSFETs (metal-oxide-semiconductor field-effect transistors) and IGBTs (insulated-gate bipolar transistors) are widely used in the power stage of switching power supplies as key switching components due to their excellent performance under high-frequency conditions. Their stable and reliable operation depends on the provision of a highly accurate switching circuit. The specific position of the power switching transistor 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 plays a crucial role in the switching power supply system. Its core design aims to prevent the reverse flow of current when the power supply fails or the device shuts down and the load exhibits capacitive characteristics, thereby effectively protecting the circuit components from damage. When constructing such a circuit, the optimized design of the switching circuit is particularly critical. It requires the power switching device to respond quickly and accurately to control commands while ensuring reliable electrical isolation from the main circuit to completely eliminate potential safety threats. Existing anti-backflow MOS transistors still have some deficiencies. The stability and accuracy of the MOS transistor gate voltage are crucial for its conduction state. However, in practical 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 transistor being unable to fully conduct or turn off, leading to a decline in circuit performance and even causing failures.

[0004] To ensure that the circuit can maintain a high degree of stability in various complex and changing operating environments and ensure its safe operation, it is particularly important to design and add an anti-backflow MOS switching circuit. The performance of the MOS switching circuit is directly related to the effectiveness of the anti-backflow protection mechanism, thus having an important impact on the reliability and stability of the entire power supply system. Therefore, there is an urgent need to develop a new type of anti-backflow MOS switching 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 the circuit performance degradation caused by the incomplete conduction or shutdown of the MOS transistor in extreme environments.

[0006] To achieve the above objective, the present invention adopts the following technical solutions to solve the problem:

[0007] An anti-backflow MOS switch circuit includes a MOS transistor, an anti-backflow voltage comparison circuit, a switch circuit, a filter voltage stabilization circuit, and a protection circuit, wherein:

[0008] The source of the MOS transistor is commonly connected to the second input terminal of the anti-backflow voltage comparison circuit, the second input terminal of the switch circuit, the second input terminal of the filter voltage stabilization circuit, and the first input terminal of the protection circuit; the drain of the MOS transistor is commonly connected to the first input terminal of the anti-backflow voltage comparison circuit and the second input terminal of the protection circuit, and the gate of the MOS transistor is commonly connected to the first output terminal of the filter voltage stabilization circuit and the first output terminal of the protection circuit; the first output terminal of the anti-backflow voltage comparison circuit is connected to the first input terminal of the switch circuit; the driving voltage VDD IsoMOS is respectively connected to the third input terminal of the anti-backflow voltage comparison circuit, the third input terminal of the filter voltage stabilization circuit, and the third input terminal of the protection circuit; the first output terminal of the switch circuit is connected to the first input terminal of the filter voltage stabilization circuit.

[0009] Further, the anti-backflow voltage comparison circuit includes a triode Q1, a triode Q2, a resistor R29, a resistor R30, and a resistor R38; wherein, the emitter of the triode Q1 is commonly connected to the base of the triode Q1, the base of the triode Q2, and one end of the resistor R29; the collector of the triode Q2 is connected to one end of the resistor R30, and the connection point is used as the first output terminal of the anti-backflow voltage comparison circuit and is connected to the first input terminal of the switch circuit; the other end of the resistor R29 is connected to the other end of the resistor R30, and the connection point is used as the third input terminal of the anti-backflow voltage comparison circuit and is commonly connected to the third input terminal of the filter voltage stabilization circuit, the third input terminal of the protection circuit, and the driving voltage VDD IsoMOS; the emitter of the triode Q2 is connected to one end of the resistor R38; the collector of the triode Q1 is used as the first input terminal of the anti-backflow voltage comparison circuit and is connected to the drain of the MOS transistor; the other end of the resistor R38 is used as the second input terminal of the anti-backflow voltage comparison circuit and is commonly connected to the source of the MOS transistor, the second input terminal of the switch circuit, the second input terminal of the filter voltage stabilization circuit, and the first input terminal of the protection circuit.

[0010] Further, the switch circuit includes a diode D7 and a triode Q15. The anode of the diode D7 is connected to the base of the triode Q15, and the connection point is used as the first input terminal of the switch circuit 3 to connect to the first output terminal of the anti-backflow voltage comparison circuit. The cathode of the diode D7 is connected to the emitter of the triode Q15, and the connection point is used as the first output terminal of the switch circuit to connect to the first input terminal of the filter voltage stabilization circuit. The collector of the triode Q15 is used as the second input terminal of the switch circuit and is commonly connected to the source of the MOS tube, the second input terminal of the anti-backflow voltage comparison circuit, the second input terminal of the filter voltage stabilization circuit, and the first input terminal of the protection circuit.

[0011] Further, the filter voltage stabilization circuit includes a diode D8, a zener diode D9, a resistor R31, and a capacitor C7. The anode of the diode D8 is connected to one end of the resistor R31, and the connection point is used as the first input terminal of the filter voltage stabilization circuit to connect to the first output terminal of the switch circuit. The other end of the resistor R31 is used as the first output terminal of the filter voltage stabilization circuit to connect to the gate of the MOS tube. The cathode of the diode D8 is connected to the cathode of the zener diode D9. The anode of the zener diode D9 is connected to one end of the capacitor C7, and the connection point is used as the second input terminal of the filter voltage stabilization circuit and is commonly connected to the source of the MOS tube, the second input terminal of the anti-backflow voltage comparison circuit, the second input terminal of the switch circuit, and the first input terminal of the protection circuit. The other end of the capacitor C7 is used as the third input terminal of the filter voltage stabilization circuit and is commonly connected to the third input terminal of the anti-backflow voltage comparison circuit and the third input terminal of the protection circuit to drive the voltage VDD IsoMOS.

[0012] Further, the protection circuit includes a voltage comparator U1 and a triode Q16. The pin 1 of the voltage comparator U1 is connected to the base of the triode Q16. The pin 2 of the voltage comparator U1 is used as the power input terminal of the voltage comparator and is commonly connected to the third input terminal of the filter voltage stabilization circuit and the third input terminal of the anti-backflow voltage comparison circuit to drive the voltage VDD IsoMOS. The pin of the voltage comparator U1 is used as the second input terminal of the protection circuit and is commonly connected to the drain of the MOS tube and the first input terminal of the anti-backflow voltage comparison circuit. The pin 4 of the voltage comparator U1 is used as the first input terminal of the protection circuit and is commonly connected to the source of the MOS, the second input terminal of the anti-backflow voltage comparison circuit, the second input terminal of the switch circuit, and the second input terminal of the filter voltage stabilization circuit. The pin 5 of the comparator U1 and the emitter of the triode Q16 are commonly connected to the source of the MOS tube. The collector of the triode Q16 is used as the first output terminal of the protection circuit and is commonly connected to the gate of the MOS tube and the first output terminal of the filter voltage stabilization circuit.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] The present invention integrates a switching circuit at both ends of the MOS transistor, real-time detects the voltage change at both ends of the MOS transistor, and determines whether to turn on the driving mechanism of the MOS transistor based on the magnitude of the detected voltage, so as to ensure that the MOS transistor can achieve efficient and precise on-off control. When the drain voltage at the output end is higher than the source voltage at the input end, the switching circuit can control the conduction states of the diode and the triode in the switching circuit according to the level of the sampled voltage, and then output an accurate driving voltage in the filter voltage stabilization circuit to be transmitted to the gate of the MOS transistor, thereby controlling the conduction state of the MOS transistor. In summary, the present invention can effectively prevent the damage of internal circuit components caused by current or voltage backflow in cases such as excessive output capacitance, abnormal output, or reverse connection of the output, significantly improve the reliability and stability of the circuit, and extend the service life of electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic structural diagram of the anti-backflow MOS switching circuit of the present invention;

[0016] Figure 2 is a circuit schematic diagram of the anti-backflow MOS switching circuit of the present invention;

[0017] The following further explains the present invention in conjunction with the drawings and specific embodiments. SPECIFIC EMBODIMENTS

[0018] As Figure 1 shown, the anti-backflow MOS switching circuit provided by the present invention includes a MOS transistor 1, an anti-backflow voltage comparison circuit 2, a switching circuit 3, a filter voltage stabilization circuit 4, and a protection circuit 5, wherein:

[0019] The source of the MOS transistor 1 is commonly connected to the second input terminal of the anti-backflow voltage comparison circuit 2, the second input terminal of the switching circuit 3, the second input terminal of the filter voltage stabilization circuit 4, and the first input terminal of the protection circuit 5; the drain of the MOS transistor 1 is commonly connected to the first input terminal of the anti-backflow voltage comparison circuit 2 and the second input terminal of the protection circuit 5, and the gate of the MOS transistor 1 is commonly connected to the first output terminal of the filter voltage stabilization circuit 4 and the first output terminal of the protection circuit 5; the first output terminal of the anti-backflow voltage comparison circuit 2 is connected to the first input terminal of the switching circuit 3; the driving voltage VDD IsoMOS is respectively connected to the third input terminal of the anti-backflow voltage comparison circuit 2, the third input terminal of the filter voltage stabilization circuit 4, and the third input terminal of the protection circuit 5; the first output terminal of the switching circuit 3 is connected to the first input terminal of the filter voltage stabilization circuit 4.

[0020] In the above technical solution, the functions of each part are as follows:

[0021] The MOS transistor 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 to which the present invention is applied;

[0022] The anti-backflow voltage comparison circuit 2 is used to collect and compare the voltages at both ends of the source and drain of the MOS transistor 1, and provide a trigger voltage for the switching circuit 3 according to the comparison result;

[0023] The switching circuit 3 is used to compare the voltage input from the anti-backflow voltage comparison circuit 2 (i.e., from the first output terminal of the anti-backflow voltage comparison circuit 2 to the first input terminal of the switching circuit 3), and output high and low level signals to the filter and voltage regulation circuit 4;

[0024] The filter and voltage regulation circuit 4 is used to filter and regulate the high and low level signals output by the switching circuit 3 (i.e., from the first output terminal of the switching circuit 3 to the first input terminal of the filter and voltage regulation circuit 4), and then provide a stable driving voltage for the gate of the MOS transistor 1.

[0025] The protection circuit 5 is used to quickly pull down the gate voltage of the MOS transistor 1 to prevent backflow current from damaging the circuit applied in the present invention when V2 is greater than V1. The protection circuit 5 provides protection for the driving circuit composed of the anti-backflow voltage comparison circuit 2, the switching circuit 3, and the filter and voltage regulation circuit 4.

[0026] VDD IsoMOS provides stable power supply for the anti-backflow voltage comparison circuit 2, the filter and voltage regulation circuit 4, and the protection circuit 5, and provides a stable input voltage for the overall of these three circuits.

[0027] As Figure 2 shown, the circuit design of this embodiment is as follows:

[0028] The anti-backflow voltage comparison circuit 2 includes a triode Q1, a triode Q2, a resistor R29, a resistor R30, and a resistor R38; wherein, the emitter of the triode Q1 is commonly connected to the base of the triode Q1, the base of the triode Q2, and one end of the resistor R29; the collector of the triode Q2 is connected to one end of the resistor R30, and the connection point is used as the first output terminal of the anti-backflow voltage comparison circuit 2 to connect to the first input terminal of the switching circuit 3; the other end of the resistor R29 is connected to the other end of the resistor R30, and the connection point is used as the third input terminal of the anti-backflow voltage comparison circuit 2 to be commonly connected to the third input terminal of the filter and voltage regulation circuit 4 and the third input terminal of the protection circuit 5 to connect to the driving voltage VDD IsoMOS; the emitter of the triode Q2 is connected to one end of the resistor R38; the collector of the triode Q1 is used as the first input terminal of the anti-backflow voltage comparison circuit 2 to connect to the drain of the MOS transistor 1; the other end of the resistor R38 is used as the second input terminal of the anti-backflow voltage comparison circuit 2, and is commonly connected to the source of the MOS transistor 1, the second input terminal of the switching circuit 3, the second input terminal of the filter and voltage regulation circuit 4, and the first input terminal of the protection circuit 5;

[0029] The switching circuit 3 includes a diode D7 and a triode Q15. Among them, the anode of the diode D7 is connected to the base of the triode Q15, and the connection endpoint serves as the first input terminal of the switching circuit 3 and is connected to the first output terminal of the anti-backflow voltage comparison circuit 2. The cathode of the diode D7 is connected to the emitter of the triode Q15, and the connection endpoint serves as the first output terminal of the switching circuit 3 and is connected to the first input terminal of the filtering and voltage stabilizing circuit 4. The collector of the triode Q15 serves as the second input terminal of the switching circuit 3 and is commonly connected to the source of the MOS transistor 1, the second input terminal of the anti-backflow voltage comparison circuit 2, the second input terminal of the filtering and voltage stabilizing circuit 4, and the first input terminal of the protection circuit 5.

[0030] The filtering and voltage stabilizing circuit 4 includes a diode D8, a zener diode D9, a resistor R31, and a capacitor C7. Among them, the anode of the diode D8 is connected to one end of the resistor R31, and the connection endpoint serves as the first input terminal of the filtering and voltage stabilizing circuit 4 and is connected to the first output terminal of the switching circuit 3. The other end of the resistor R31 serves as the first output terminal (DRV IsoMOS) of the filtering and voltage stabilizing circuit 4 and is connected to the gate of the MOS transistor 1. The cathode of the diode D8 is connected to the cathode of the zener diode D9. The anode of the zener diode D9 is connected to one end of the capacitor C7, and the connection endpoint serves as the second input terminal of the filtering and voltage stabilizing circuit 4 and is commonly connected to the source of the MOS transistor 1, the second input terminal of the anti-backflow voltage comparison circuit 2, the second input terminal of the switching circuit 3, and the first input terminal of the protection circuit 5. The other end of the capacitor C7 serves as the third input terminal of the filtering and voltage stabilizing circuit 4 and is commonly connected to the third input terminal of the anti-backflow voltage comparison circuit 2 and the third input terminal of the protection circuit 5 to drive the voltage VDD IsoMOS.

[0031] The protection circuit 5 includes a voltage comparator U1 and a triode Q16. Among them, the pin 1 of the voltage comparator U1 is connected to the base of the triode Q16, and the pin 2 of the voltage comparator U1 serves as the power input terminal of the voltage comparator and is commonly connected to the third input terminal of the filtering and voltage stabilizing circuit 4 and the third input terminal of the anti-backflow voltage comparison circuit 2 to drive the voltage VDD IsoMOS. The pin 3 of the voltage comparator U1 serves as the second input terminal of the protection circuit 5 and is commonly connected to the drain of the MOS transistor 1 and the first input terminal of the anti-backflow voltage comparison circuit 2. The pin 4 of the voltage comparator U1 serves as the first input terminal of the protection circuit 5 and is commonly connected to the source of the MOS transistor 1, the second input terminal of the anti-backflow voltage comparison circuit 2, the second input terminal of the switching circuit 3, and the second input terminal of the filtering and voltage stabilizing circuit 4. The pin 5 of the comparator U1 and the emitter of the triode Q16 are commonly connected to the source of the MOS transistor 1, and the collector of the triode Q16 serves as the first output terminal of the protection circuit 5 and is commonly connected to the gate of the MOS transistor 1 and the first output terminal of the filtering and voltage stabilizing circuit 4.

[0032] In this embodiment, the selection of each component is as follows:

[0033] The triodes Q1 and Q2 can be integrated components of model MMDT5551, or two discrete components of triodes with the same PN junction characteristics can be integrated into one component;

[0034] The value of the resistor R29 is 5 to 20 kΩ;

[0035] The value of the resistor R30 is 7 to 20 kΩ;

[0036] The value of the resistor R38 is 33 Ω;

[0037] The diodes D7 and D8 are Schottky diodes or fast recovery diodes, and their models are both BAS516;

[0038] The model of the triode Q15 is MMBT4403;

[0039] The value of the resistor R31 is 0.1 Ω;

[0040] The diode D9 is a zener diode, and its model is BZX585_B13;

[0041] The model of the capacitor C7 is 1 uF;

[0042] The model of the triode Q16 can be the same as that of the triodes Q1 and Q2, and the model is MMBT5551;

[0043] The model of the voltage comparator U1 is LMV7219M5 / TR.

[0044] The working principle of the present invention is as follows:

[0045] When the present invention is in use, the MOS transistor 1 is connected to the circuit to which the present invention is applied. In actual application, the current in the circuit flows into the source and drain of the MOS transistor 1 in sequence.

[0046] Such as Figure 2As shown, the input voltage V1 and the output voltage V2 across the MOS transistor 1 are detected by the anti-backflow voltage comparison circuit 2. When the input voltage V1 is greater than the output voltage V2, since the first terminal emitter of the triode Q1 is connected to the second terminal base, the triode Q1 cannot obtain sufficient bias voltage to remain in the cut-off state, and its emitter is connected to the base of the triode Q2. Since the base voltage of the triode Q2 is lower than the emitter voltage, the triode Q2 cannot conduct 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 switching circuit 3 in sequence, and continue to flow into the filter voltage stabilization circuit 4. Through the combined action of the diode D8 and the zener diode D9, the output voltage is stably controlled between 10V and 15V, and flows out as a high-level signal from DRV IsoMOS to provide the necessary supply voltage for the gate of the MOS transistor 1. At this time, the protection circuit does not act, thus ensuring its normal conduction.

[0047] When the input voltage V1 is less than the output voltage V2, the connection state of the integrated components of the triode Q1 and the triode Q2 remains unchanged, and the triode Q1 is still cut off. However, at this time, the base voltage of the triode Q2 is higher than its emitter voltage, so the triode Q2 starts to conduct. As a result, the current provided by VDD IsoMOS, after flowing through the resistor R30, no longer flows to the filter voltage stabilization circuit 4, 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 the triode Q2 is pulled down to V1, the triode Q15 in the switching circuit 3 obtains sufficient bias voltage to conduct. 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 transistor 1 is not sufficient to reach its conduction voltage, the MOS transistor 1 will turn off, and through the action of the voltage comparator U1, its output is high level, which causes the triode Q16 to conduct, pulling down the DRV IsoMOS voltage to V1, effectively preventing the reverse flow of the backflow current into the switching power supply, thus protecting the safe and stable operation of the entire circuit system.

[0048] Advantages of the present invention: The switching circuit of a general anti-backflow MOS is relatively simple and has low stability. Especially under certain extreme conditions, there may still be a problem of backflow current. The anti-backflow MOS switching circuit of the present invention has the characteristic of low power consumption during operation, ensuring high utilization efficiency of the circuit during continuous operation. Secondly, the circuit has excellent fast response ability 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 anti-backflow MOS switching circuit of the present invention can quickly detect the change and output a suitable driving voltage in a timely manner, thereby effectively driving the MOS transistor to turn off and preventing the generation of backflow current, protecting the safe and stable operation of the entire circuit system.

[0049] As shown above, the technical effects of the present invention are as follows:

[0050] (1) The switching circuit of a general anti-backflow MOS is relatively simple and has low stability. Especially under certain extreme conditions, there may still be a problem of backflow current. The anti-backflow MOS switching circuit of the present invention has the characteristic of low power consumption during operation, ensuring high utilization efficiency of the circuit during continuous operation.

[0051] (2) Secondly, the circuit of the present invention has excellent fast response ability 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 switching circuit 3 can quickly detect the change and output a suitable driving voltage in a timely manner, thereby effectively driving the MOS transistor to turn off and preventing the generation of backflow current, protecting the safe and stable operation of the entire circuit system.

[0052] The above is only the preferred embodiment of the present invention. It should be noted that the above preferred embodiment should not be regarded as a limitation of the present invention. For those of ordinary skill in the art of this technology, without departing from the scope of the present invention, several improvements can be made. Without departing from the purpose and scope of the technical solution of the present invention, they should all be covered within the scope of the claims of the present invention.

Claims

1. An anti-backflow MOS switch circuit, characterized in that, It includes a MOS transistor (1), an anti-backflow voltage comparison circuit (2), a switching circuit (3), a filtering and voltage stabilizing circuit (4), and a protection circuit (5), where: The source electrode of the MOS transistor (1) is commonly connected to the second input terminal of the anti-backflow voltage comparison circuit (2), the second input terminal of the switching circuit (3), the second input terminal of the filtering and voltage stabilizing circuit (4), and the first input terminal of the protection circuit (5); the drain electrode of the MOS transistor (1) is commonly connected to the first input terminal of the anti-backflow voltage comparison circuit (2) and the second input terminal of the protection circuit (5), and the gate electrode of the MOS transistor (1) is commonly connected to the first output terminal of the filtering and voltage stabilizing circuit (4) and the first output terminal of the protection circuit (5); the first output terminal of the anti-backflow voltage comparison circuit (2) is connected to the first input terminal of the switching circuit (3); the driving voltage VDD IsoMOS is respectively connected to the third input terminal of the anti-backflow voltage comparison circuit (2), the third input terminal of the filtering and voltage stabilizing circuit (4), and the third input terminal of the protection circuit (5); the first output terminal of the switching circuit (3) is connected to the first input terminal of the filtering and voltage stabilizing circuit (4); The anti-backflow voltage comparison circuit (2) includes a triode Q1, a triode Q2, a resistor R29, a resistor R30, and a resistor R38; where, the emitter electrode of the triode Q1 is commonly connected to the base electrode of the triode Q1, the base electrode of the triode Q2, and one end of the resistor R29; the collector electrode of the triode Q2 is connected to one end of the resistor R30, and the connection end point serves as the first output terminal of the anti-backflow voltage comparison circuit (2) and is connected to the first input terminal of the switching circuit (3); the other end of the resistor R29 is connected to the other end of the resistor R30, and the connection end point serves as the third input terminal of the anti-backflow voltage comparison circuit (2) and is commonly connected to the third input terminal of the filtering and voltage stabilizing circuit (4), the third input terminal of the protection circuit (5) to drive the voltage VDD IsoMOS; the emitter electrode of the triode Q2 is connected to one end of the resistor R38; the collector electrode of the triode Q1 serves as the first input terminal of the anti-backflow voltage comparison circuit (2) and is connected to the drain electrode of the MOS transistor (1); the other end of the resistor R38 serves as the second input terminal of the anti-backflow voltage comparison circuit (2) and is commonly connected to the source electrode of the MOS transistor (1), the second input terminal of the switching circuit (3), the second input terminal of the filtering and voltage stabilizing circuit (4), and the first input terminal of the protection circuit (5); The protection circuit (5) includes a voltage comparator U1 and a triode Q16. Among them, the 1-pin of the voltage comparator U1 is connected to the base of the triode Q16. The 2-pin of the voltage comparator U1 serves as the power input terminal of the voltage comparator and is commonly connected to the drive voltage VDD IsoMOS together with the third input terminal of the filter voltage stabilization circuit (4) and the third input terminal of the anti-backflow voltage comparison circuit (2). The 3-pin of the voltage comparator U1 serves as the second input terminal of the protection circuit (5) and is commonly connected to the drain of the MOS transistor (1) and the first input terminal of the anti-backflow voltage comparison circuit (2). The 4-pin of the voltage comparator U1 serves as the first input terminal of the protection circuit (5) and is commonly connected to the source of the MOS transistor (1), the second input terminal of the anti-backflow voltage comparison circuit (2), the second input terminal of the switch circuit (3), and the second input terminal of the filter voltage stabilization circuit (4). The 5-pin of the comparator U1 and the emitter of the triode Q16 are commonly connected to the source of the MOS transistor (1). The collector of the triode Q16 serves as the first output terminal of the protection circuit (5) and is commonly connected to the gate of the MOS transistor (1) and the first output terminal of the filter voltage stabilization circuit (4).

2. The anti-backflow MOS switch circuit according to claim 1, characterized in that, The switch circuit (3) includes a diode D7 and a triode Q15. Among them, the anode of the diode D7 is connected to the base of the triode Q15, and the connection point serves as the first input terminal of the switch circuit (3) and is connected to the first output terminal of the anti-backflow voltage comparison circuit (2). The cathode of the diode D7 is connected to the emitter of the triode Q15, and the connection point serves as the first output terminal of the switch circuit (3) and is connected to the first input terminal of the filter voltage stabilization circuit (4). The collector of the triode Q15 serves as the second input terminal of the switch circuit (3) and is commonly connected to the source of the MOS transistor (1), the second input terminal of the anti-backflow voltage comparison circuit (2), the second input terminal of the filter voltage stabilization circuit (4), and the first input terminal of the protection circuit (5).

3. The anti-backflow MOS switch circuit according to claim 2, characterized in that, The filter voltage stabilization circuit (4) includes a diode D8, a zener diode D9, a resistor R31, and a capacitor C7. Among them, the anode of the diode D8 is connected to one end of the resistor R31, and the connection point serves as the first input terminal of the filter voltage stabilization circuit (4) and is connected to the first output terminal of the switch circuit (3). The other end of the resistor R31 serves as the first output terminal of the filter voltage stabilization circuit (4) and is connected to the gate of the MOS transistor (1). The cathode of the diode D8 is connected to the cathode of the zener diode D9. The anode of the zener diode D9 is connected to one end of the capacitor C7, and the connection point serves as the second input terminal of the filter voltage stabilization circuit (4) and is commonly connected to the source of the MOS transistor (1), the second input terminal of the anti-backflow voltage comparison circuit (2), the second input terminal of the switch circuit (3), and the first input terminal of the protection circuit (5). The other end of the capacitor C7 serves as the third input terminal of the filter voltage stabilization circuit (4) and is commonly connected to the third input terminal of the anti-backflow voltage comparison circuit (2) and the third input terminal of the protection circuit (5) to connect the drive voltage VDD IsoMOS.

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