Anti-inrush high-voltage starting circuit

Abstract

The application discloses a kind of anti-inversion high-voltage starting circuit, including first voltage divider circuit, starting current generating circuit, anti-inversion circuit, second voltage divider circuit and threshold comparison circuit;The first voltage divider circuit is used to detect the input voltage of VIN end, and generates negative input voltage AVIN by voltage division;The starting current generating circuit is used to generate starting current;The anti-inversion circuit is used to generate mirror current, and block the inversion current of VDD end flowing to VIN end;The second voltage divider circuit is used to detect the output voltage of VDD end, and generates first positive input voltage AVDD1 and second positive input voltage AVDD2 by voltage division;The threshold comparison circuit includes comparator COMP1 and comparator COMP2;The voltage of VIN end and VDD end is detected by the first voltage divider circuit and the second voltage divider circuit in the application by voltage division, the voltage size of VIN and VDD is monitored in real time, and the current inversion problem when VIN is less than VDD and VDD does not exceed the voltage threshold can be effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuits, and specifically relates to a high-voltage start-up circuit for preventing backflow. Background Technology

[0002] Switching power supplies, as a highly efficient power supply technology, are widely used in various electronic products and devices due to their excellent energy-saving characteristics. A switching power supply converter consists of two parts: a control module and a power module. The control module of the switching power supply converter adjusts the power module in a timely manner according to changes in input and output conditions (voltage or current), converting one form of power supply to another. Generally, a switching power supply converter requires a startup circuit to provide regulated power to the control module when the converter is first powered on. The converter only begins operation after the control module is functioning normally. In related technologies, a resistor is typically used to charge a capacitor. When the capacitor voltage reaches the startup voltage, power is supplied to the control module. The power consumption of the startup circuit depends on the resistance value; a larger resistance results in lower power consumption but a longer startup time, while a smaller resistance results in a shorter startup time but higher power consumption. Therefore, this charging method requires a trade-off between startup time and power consumption.

[0003] In existing technologies, the startup of switching power supply control chips is achieved through startup resistors or high-voltage startup circuits. However, to achieve high efficiency and energy saving, the energy consumption introduced by the startup resistor method cannot be ignored. Theoretically, energy consumption can be reduced by increasing the startup resistor, but this will lead to a significant increase in startup time. The design concept of the high-voltage startup circuit is that during the system startup phase, the high-voltage input terminal provides a startup current to the bypass capacitor C of the VDD pin. VDD During charging, when VDD exceeds the threshold voltage of the overvoltage protection module, the startup current is shut off, and the VDD pin is powered by the auxiliary winding of the external transformer.

[0004] Traditional high-voltage starting circuits, such as Figure 1 As shown, when VIN > VDD and VDD does not exceed the voltage threshold, the xEN signal is low and VDDOVP is high, and the VIN terminal provides startup current to charge the VDD terminal. When VIN > VDD and VDD exceeds the voltage threshold, the xEN signal is high and VDDOVP is low, the startup circuit is turned off, and the external surround group supplies power to the VDD port. At this time, the anti-backflow diode PM3 is turned off, and even if VDD > VIN, there is no backflow current in the startup circuit. However, when VIN < VDD and VDD does not exceed the voltage threshold, the anti-backflow diode PM3 is in the on state, and the parasitic diode does not function. At this time, a large backflow current will be generated from the VDD terminal to the VIN terminal, affecting the system operation. Summary of the Invention

[0005] This invention aims to overcome at least one defect (insufficiency) in the prior art. It uses voltage divider resistors to detect the voltage at the VIN and VDD terminals respectively, and compares the two through comparator COMP2 to monitor the voltage magnitude of VIN and VDD in real time. The output of comparator COMP2 is synchronously used as the enable signal for the startup circuit. When VIN < VDD and VDD does not exceed the voltage threshold, the anti-backflow tube PM3 is turned off, and the parasitic diode is used to block the backflow current, thereby solving the current backflow problem when VIN < VDD and VDD does not exceed the voltage threshold, and has no impact on the high-voltage startup function when VIN > VDD.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides an anti-backflow high-voltage starting circuit, the anti-backflow high-voltage starting circuit comprising:

[0008] The circuit consists of a first voltage divider circuit, a starting current generation circuit, an anti-backflow circuit, a second voltage divider circuit, and a threshold comparison circuit.

[0009] The first voltage divider circuit is used to detect the input voltage at the VIN terminal and divide the voltage to generate a negative input voltage AVIN;

[0010] The starting current generating circuit is used to generate a starting current;

[0011] The backflow prevention circuit is used to generate a mirror current and block the backflow current flowing from the VDD terminal to the VIN terminal.

[0012] The second voltage divider circuit is used to detect the output voltage at the VDD terminal and divide the voltage to generate the first positive input voltage AVDD1 and the second positive input voltage AVDD2.

[0013] The threshold comparison circuit includes comparator COMP1 and comparator COMP2;

[0014] The comparator COMP1 is used to detect whether the first positive input voltage is greater than the reference voltage, and controls the shutdown of the anti-backflow circuit and the starting current generation circuit when it is confirmed that the first positive input voltage is greater than the reference voltage; the comparator COMP2 is used to compare the negative input voltage AVIN and the second positive input voltage AVDD2, and controls the shutdown of the anti-backflow circuit when it is confirmed that the second positive input voltage AVDD2 is greater than the negative input voltage AVIN.

[0015] Optionally, the first voltage divider circuit includes resistors R1 and R2. The first end of resistor R1 is connected to the VIN terminal, the second end of resistor R1 is connected to the first end of resistor R2, the second end of resistor R2 is connected to ground, and the output point of the negative input voltage AVIN is the connection point of resistors R1 and R2.

[0016] Optionally, the startup current generation circuit includes a resistor R3, a diode D1, a switching transistor NM3, a switching transistor NM1, a switching transistor PM1, and a reference current source IREF; the gate of the switching transistor NM3 is connected to an enable signal xEN to control the switching transistor NM3 to turn on and off.

[0017] When the enable signal xEN is high, the switch NM3 is turned off, and the starting current generation circuit does not work.

[0018] When the enable signal xEN is low, the switch NM3 is turned on, and the starting current generation circuit is activated.

[0019] Optionally, the anti-backflow circuit includes diode D2, switching transistor PM2, switching transistor PM3, resistor R4, resistor R5, and switching transistor NM2; the gate of switching transistor NM2 is connected to an enable signal VDDOVP to control the switching transistor NM2 to turn on and off.

[0020] When the enable signal VDDOVP is high, the switch NM2 is turned on, which in turn turns on the switch PM3, and the starting current flows from the VIN terminal to the VDD terminal.

[0021] When the enable signal VDDOVP is low, the switch NM2 is turned off, which in turn turns off the switch PM3, blocking the backflow current from the VDD terminal to the VIN terminal.

[0022] Optionally, the second voltage divider circuit includes resistors R6, R7, and R8. The first end of resistor R6 is connected to the VDD terminal, and the second end of resistor R6 is connected to the ground terminal through resistors R7 and R8 in sequence. The output point of the first positive input voltage is the connection point of resistors R6 and R7, and the output point of the second positive input voltage is the connection point of resistors R7 and R8.

[0023] Optionally, one end of resistor R3 is electrically connected to the VIN terminal, and the second end of resistor R3 is connected to the cathode of diode D1, the drain of switching transistor NM3, and the gate of switching transistor NM3, respectively. The anode of diode D1 is electrically connected to the source and GND terminal of switching transistor NM3, and the gate of switching transistor NM3 is connected to the enable signal xEN. The source of switching transistor PM1 is electrically connected to the VIN terminal, and both the gate and drain of switching transistor PM1 are connected to the anti-backflow circuit. The source of switching transistor NM1 is electrically connected to one end of the reference current source IREF. The second end of the reference current source IREF is electrically connected to the GND terminal.

[0024] Optionally, the cathode of diode D2 is electrically connected to the VIN terminal, and the anode of diode D2 is connected to the gate of switching transistor PM2 and the startup current generating circuit; the source of switching transistor PM2 is electrically connected to the VIN terminal, the drain of switching transistor PM2 is electrically connected to the drain of switching transistor PM3, the gate of switching transistor PM3 is electrically connected to the first terminal of resistor R4 and the first terminal of resistor R5, the source of switching transistor PM3 is connected to the second terminal of resistor R4 and the VDD terminal, the second terminal of resistor R5 is electrically connected to the drain of switching transistor NM2, the gate of switching transistor NM2 is connected to the enable signal VDDOVP, and the source of switching transistor NM2 is electrically connected to the GND terminal.

[0025] Optionally, the threshold comparison circuit further includes inverters INV1 and INV2 and an AND gate. The non-inverting input of comparator COMP1 is connected to the first positive input voltage AVDD1, and the inverting input of comparator COMP1 is connected to the reference voltage VREF. The output of comparator COMP1 is electrically connected to the input of inverter INV1. The output of inverter INV1 is electrically connected to the first terminal of the AND gate. The non-inverting input of comparator COMP2 is connected to the second positive input voltage AVDD2, and the inverting input of comparator COMP2 is connected to the negative input voltage AVIN. The output of comparator COMP2 is electrically connected to the input of inverter INV2, and the output of inverter INV2 is electrically connected to the second terminal of the AND gate. The output of the AND gate outputs an enable signal VDDOVP.

[0026] The beneficial effects of this invention are as follows:

[0027] This invention uses a first voltage divider circuit and a second voltage divider circuit to detect the voltages at the VIN and VDD terminals respectively. The voltages are then compared using comparator COMP2 in the threshold comparison circuit to monitor the magnitudes of VIN and VDD in real time. The output of comparator COMP2 is synchronously used as the enable signal for the startup circuit. When VIN < VDD and VDD does not exceed the voltage threshold, the anti-backflow switch PM3 is turned off, and the parasitic diode blocks the backflow current, effectively solving the problem of backflow current when VIN < VDD and VDD does not exceed the voltage threshold. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a traditional high-voltage starting circuit.

[0029] Figure 2 This is a circuit schematic diagram of an embodiment of the present invention;

[0030] Figure 3 This is a simulation diagram of the reverse current from VDD to VIN in a traditional high-voltage starting circuit under the conditions of VIN=9V and VDD=9~25V.

[0031] Figure 4 This is a simulation diagram of the reverse current from VDD to VIN under the conditions of VIN=9V and VDD=9~25V in an embodiment of the present invention;

[0032] Figure 5 This is a simulation diagram of the starting current from VIN to VDD under the conditions of VIN = 9~100V and VDD = 8V in an embodiment of the present invention;

[0033] Figure 6 This is a simulation diagram of the starting current from VIN to VDD under the conditions of VIN = 9~100V and VDD = 12V, according to an embodiment of the present invention. Detailed Implementation

[0034] The present invention and its beneficial effects will be further described in detail below with reference to specific embodiments and accompanying drawings. However, the specific embodiments of the present invention are not limited thereto.

[0035] Figure 2 This is a circuit schematic diagram of an embodiment of the present invention. The embodiment of the present invention provides an anti-backflow high-voltage starting circuit, which specifically includes a first voltage divider circuit 100, a starting current generating circuit 200, an anti-backflow circuit 300, a second voltage divider circuit 400, and a threshold comparison circuit 500.

[0036] The first voltage divider circuit 100 is used to detect the input voltage at the VIN terminal and divide the voltage to generate a negative input voltage AVIN;

[0037] The starting current generating circuit 200 is used to generate the starting current.

[0038] The anti-backflow circuit 300 is used to generate a mirror current and block the backflow current from the VDD terminal to the VIN terminal.

[0039] The second voltage divider circuit 400 is used to detect the output voltage at the VDD terminal and divide the voltage to generate the first positive input voltage AVDD1 and the second positive input voltage AVDD2.

[0040] The threshold comparison circuit 500 includes comparator COMP1 and comparator COMP2;

[0041] Comparator COMP1 is used to detect whether the first positive input voltage is greater than the reference voltage, and controls the shutdown of the anti-backflow circuit 300 and the starting current generation circuit 200 when it is confirmed that the first positive input voltage is greater than the reference voltage; comparator COMP2 is used to compare the negative input voltage AVIN and the second positive input voltage AVDD2, and controls the shutdown of the anti-backflow circuit 300 when it is confirmed that the second positive input voltage AVDD2 is greater than the negative input voltage AVIN.

[0042] In this embodiment, the first voltage divider circuit 100 includes resistor R1 and resistor R2; one end of resistor R1 is electrically connected to the VIN terminal, the second end is electrically connected to one end of resistor R2, and is also electrically connected to the inverting input terminal of comparator COMP2; the second end of resistor R2 is electrically connected to the GND terminal.

[0043] The starting current generation circuit 200 includes resistor R3, diode D1, switching transistors NM3 and NM1, switching transistor PM1, and reference current source I. REF One end of resistor R3 is electrically connected to the VIN terminal, and the second end is electrically connected to the cathode of diode D1 and the drain of switching transistor NM3, and also electrically connected to the gate of switching transistor NM1; the anode of diode D1 is electrically connected to the source of switching transistor NM3, and also electrically connected to the GND terminal; the gate of switching transistor NM3 is electrically connected to the output of comparator COMP1 and the input of inverter INV1; the source of switching transistor PM1 is electrically connected to the VIN terminal, and its gate is electrically connected to its drain and the drain of switching transistor NM1, and also electrically connected to the anode of diode D2 and the gate of switching transistor PM2; the source of the high-voltage NMOS switching transistor is connected to the reference current source I. REF One end is electrically connected; reference current source I REF The second terminal is electrically connected to the GND terminal;

[0044] The anti-backflow circuit 300 includes diode D2, switching transistor PM2, switching transistor PM3, resistors R4 and R5, and switching transistor NM2. The cathode of diode D2 is electrically connected to the VIN terminal, and the anode is electrically connected to the gate of switching transistor PM2. It is also electrically connected to the gate and drain of switching transistor PM1 and the drain of switching transistor NM1. The source of switching transistor PM2 is electrically connected to the VIN terminal, and the drain is electrically connected to the drain of switching transistor PM3. The gate of switching transistor PM3 is electrically connected to one end of resistors R4 and R5, and the source is electrically connected to the second end of resistor R4 and one end of resistor R6. It is also electrically connected to the VDD output terminal. The second end of resistor R5 is electrically connected to the drain of switching transistor NM2. The gate of switching transistor NM2 is electrically connected to the output terminal of the AND gate, and the source is electrically connected to the GND terminal.

[0045] The second voltage divider circuit 400 includes resistors R6, R7, and R8; one end of resistor R6 is electrically connected to one end of resistor R4 and the source of switching transistor PM3, and is also electrically connected to the VDD output terminal; the second end of resistor R6 is electrically connected to one end of resistor R7 and the non-inverting input terminal of comparator COMP1; the second end of resistor R7 is electrically connected to one end of resistor R8 and the non-inverting input terminal of comparator COMP2; the second end of resistor R8 is electrically connected to the GND terminal.

[0046] The threshold comparison circuit 500 includes comparators COMP1 and COMP2, inverters INV1 and INV2, and an AND gate; the non-inverting input of comparator COMP1 is electrically connected to one end of resistors R6 and R7, and the inverting input is connected to the reference voltage V. REF Electrical connections are established: the output terminal is electrically connected to the input terminal of inverter INV1; the output terminal of inverter INV1 is electrically connected to one end of AND gate; the non-inverting input terminal of comparator COMP2 is electrically connected to one end of resistors R7 and R8, the inverting input terminal is electrically connected to one end of resistors R1 and R2, and the output terminal is electrically connected to the input terminal of inverter INV2; the output terminal of inverter INV2 is electrically connected to the second end of AND gate; and the output terminal of AND gate is electrically connected to the gate of switching transistor NM2.

[0047] The working principle of this embodiment is as follows:

[0048] When the startup circuit is first powered on, the voltage at the VDD terminal is low. At this time, the comparator is enabled and outputs a low level by default. Therefore, xEN is low, VDDOVP is high, and the switching transistor NM2 is turned on. As the VIN voltage rises, V... DZ The voltage rises accordingly, when V DZ The threshold voltage V of the switching transistor NM1 is greater than TH When NM1 is turned on, I REFThe current is reflected by the current mirrors PM1 and PM2, generating a starting current that begins to charge the VDD terminal. As the VDD voltage gradually rises, comparators COMP1 and COMP2 are de-enabled and begin normal operation.

[0049] When VIN > VDD and VDD does not exceed the voltage threshold, the comparator COMP1 output signal xEN is low and the comparator COMP2 output signal is high. Therefore, the VDDOVP signal is high, the startup circuit operates normally, the anti-backflow tube PM3 is turned on, and V... GS =VDD*R5 / (R4+R5), the starting current continues to charge the VDD port; when VIN>VDD, and VDD exceeds the voltage threshold, the comparator COMP1 output signal xEN is high, the comparator COMP2 output signal is high, then the VDDOVP signal is low, the switching transistor NM1 is turned on, and V... DZ Pulled down to GND, switch NM2 turns off, backflow prevention switch PM3 turns off, V GS =VDD, the startup circuit is off, there is no startup current, and the VDD terminal is powered by the external winding group. At this time, if the VDD voltage is greater than the VIN voltage, the reverse current from the VDD terminal to the VIN terminal is blocked through the parasitic diode.

[0050] When the VIN voltage is less than the VDD overvoltage threshold, the startup circuit works normally during the initial power-on phase, and there is still a startup current charging the VDD terminal. The VDD voltage gradually rises to near the VIN voltage. The comparator COMP1 output signal xEN is low, and the comparator COMP2 output signal is high. Then the VDDOVP signal is low, the anti-backflow tube PM3 is turned off, VGS = VDD, and the backflow current from the VDD terminal to the VIN terminal is blocked through the parasitic diode. The maximum VDD voltage is equal to VIN.

[0051] The traditional high-voltage startup circuit and the high-voltage startup circuit of this embodiment were designed and simulated using DB HiTek 0.18um 100V technology. In the DC simulation diagram, Ivdd_vin represents the reverse current from VDD to VIN, and Ivin_vdd represents the startup current from VIN to VDD.

[0052] Figure 3 The figure shows the simulated waveform of the reverse current from VDD terminal to VIN terminal in a traditional high-voltage starting circuit under the conditions of VIN=9V and VDD=9~25V. When VDD<VIN and does not exceed the voltage threshold of 9.96V, the maximum reverse current from VDD terminal to VIN terminal can reach 66.416mA. Figure 4The figure shows the simulated waveform of the reverse current from VDD terminal to VIN terminal under the conditions of VIN=9V and VDD=9~25V in an embodiment of the present invention. When VDD<VIN and does not exceed the voltage threshold of 9.96V, the maximum reverse current from VDD terminal to VIN terminal is only 114.8pA. Figure 5 The figure shows the simulated waveform of the starting current from VIN to VDD under the conditions of VIN = 9~100V and VDD = 8V in an embodiment of the present invention. The high-voltage starting function is normal. Figure 6 The figure shows the simulated waveform of the starting current from VIN to VDD under the conditions of VIN = 9~100V and VDD = 12V in an embodiment of the present invention. When VDD < VIN and exceeds the voltage threshold, the starting circuit is shut down and the maximum starting current from VIN to VDD is only 284.2pA.

[0053] Simulation results show that the high-voltage circuit of this embodiment can normally realize the high-voltage start-up function under the condition of VIN>VDD. Moreover, compared with the traditional high-voltage start-up circuit, when VIN<VDD and VDD does not exceed the voltage threshold, it can solve the problem of reverse current flowing from VDD terminal to VIN terminal.

[0054] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limitations on the present invention. For those skilled in the art, several equivalent substitutions, improvements and modifications can be made without departing from the spirit and scope of the present invention. These equivalent substitutions, improvements and modifications should also be regarded as the protection scope of the present invention. Here, the embodiments will not be repeated. The protection scope of the present invention should be determined by the scope defined in the claims.

Claims

1. A high-voltage starting circuit for preventing backflow, characterized in that, The anti-backflow high-voltage starting circuit includes a first voltage divider circuit, a starting current generating circuit, an anti-backflow circuit, a second voltage divider circuit, and a threshold comparison circuit. The first voltage divider circuit is used to detect the input voltage at the voltage input terminal and divide the voltage to generate a negative input voltage AVIN; The starting current generating circuit is used to generate a starting current; The backflow prevention circuit is used to generate a mirror current and block the backflow current flowing from the voltage output terminal to the voltage input terminal. The second voltage divider circuit is used to detect the output voltage at the voltage output terminal and divide the voltage to generate a first positive input voltage and a second positive input voltage, wherein the first positive input voltage is greater than the second positive input voltage; The threshold comparison circuit includes comparator COMP1 and comparator COMP2; The comparator COMP1 is used to detect whether the first positive input voltage is greater than the reference voltage, and when it is confirmed that the first positive input voltage is greater than the reference voltage, it controls the shutdown of the anti-backflow circuit and the starting current generation circuit. The comparator COMP2 is used to compare the negative input voltage AVIN with the second positive input voltage, and to control the shutdown of the anti-backflow circuit when it is confirmed that the second positive input voltage is greater than the negative input voltage AVIN. The output terminal of the first voltage divider circuit is connected to the first input terminal of the threshold comparison circuit. The starting current generating circuit is connected to the anti-backflow circuit. The output terminal of the anti-backflow circuit is connected to the input terminal of the second voltage divider circuit. The first output terminal of the second voltage divider circuit outputs the first positive input voltage and transmits it to the second input terminal of the threshold comparison circuit. The second output terminal of the second voltage divider circuit outputs the second positive input voltage and transmits it to the third input terminal of the threshold comparison circuit. The first output terminal of the threshold comparison circuit outputs an enable signal xEN and transmits it to the control terminal of the starting current generating circuit. The second output terminal of the threshold comparison circuit outputs an enable signal VDDOVP and transmits it to the control terminal of the anti-backflow circuit.

2. The anti-backflow high-voltage starting circuit according to claim 1, characterized in that, The first voltage divider circuit includes resistors R1 and R2. The first end of resistor R1 is connected to the voltage input terminal, the second end of resistor R1 is connected to the first end of resistor R2, and the second end of resistor R2 is connected to ground. The output point of the negative input voltage AVIN is the connection point of resistors R1 and R2.

3. The anti-backflow high-voltage starting circuit according to claim 1, characterized in that, The starting current generating circuit includes resistor R3, diode D1, switching transistors NM3, NM1, PM1, and reference current source I. REF The gate of the switching transistor NM3 is connected to an enable signal xEN to control the switching transistor NM3 to turn on and off. When the enable signal xEN is high, the switch NM3 is turned off, and the starting current generation circuit does not work. When the enable signal xEN is low, the switch NM3 is turned on, and the starting current generation circuit is activated.

4. The anti-backflow high-voltage starting circuit according to claim 1, characterized in that, The backflow prevention circuit includes diode D2, switching transistor PM2, switching transistor PM3, resistor R4, resistor R5, and switching transistor NM2; the gate of switching transistor NM2 is connected to an enable signal VDDOVP to control the switching transistor NM2 to turn on and off. When the enable signal VDDOVP is high, the switch NM2 is turned on, which in turn turns on the switch PM3, and the starting current flows from the voltage input terminal to the voltage output terminal. When the enable signal VDDOVP is low, the switch NM2 is turned off, which in turn turns off the switch PM3, blocking the reverse current flowing from the voltage output terminal to the voltage input terminal.

5. The anti-backflow high-voltage starting circuit according to claim 1, characterized in that, The second voltage divider circuit includes resistors R6, R7, and R8. The first end of resistor R6 is connected to the voltage output terminal, and the second end of resistor R6 is connected to ground through resistors R7 and R8 in sequence. The output point of the first positive input voltage is the connection point of resistors R6 and R7, and the output point of the second positive input voltage is the connection point of resistors R7 and R8.

6. The anti-backflow high-voltage starting circuit according to claim 3, characterized in that: One end of resistor R3 is electrically connected to the voltage input terminal. The second end of resistor R3 is connected to the cathode of diode D1, the drain of switching transistor NM3, and the gate of switching transistor NM3. The anode of diode D1 is electrically connected to the source and GND terminal of switching transistor NM3. The gate of switching transistor NM3 is connected to the enable signal xEN. The source of switching transistor PM1 is electrically connected to the voltage input terminal. The gate and drain of switching transistor PM1 are both connected to the anti-reverse current circuit. The source of switching transistor NM1 is connected to the reference current source I. REF One end is electrically connected; the reference current source I REF The second terminal is electrically connected to the GND terminal.

7. The anti-backflow high-voltage starting circuit according to claim 4, characterized in that: The cathode of diode D2 is electrically connected to the voltage input terminal, and the anode of diode D2 is connected to the gate of switching transistor PM2 and the starting current generating circuit. The source of switching transistor PM2 is electrically connected to the voltage input terminal, and the drain of switching transistor PM2 is electrically connected to the drain of switching transistor PM3. The gate of switching transistor PM3 is electrically connected to the first end of resistor R4 and the first end of resistor R5, respectively. The source of switching transistor PM3 is connected to the second end of resistor R4 and the voltage output terminal. The second end of resistor R5 is electrically connected to the drain of switching transistor NM2. The gate of switching transistor NM2 is connected to the enable signal VDDOVP, and the source of switching transistor NM2 is electrically connected to the GND terminal.

8. The anti-backflow high-voltage starting circuit according to claim 1, characterized in that: The threshold comparison circuit further includes inverters INV1 and INV2 and an AND gate. The non-inverting input of comparator COMP1 is connected to the first positive input voltage, and the inverting input of comparator COMP1 is connected to the reference voltage. The output of comparator COMP1 is electrically connected to the input of inverter INV1, and the output of comparator COMP1 outputs an enable signal xEN. The output of inverter INV1 is electrically connected to the first terminal of the AND gate. The non-inverting input of comparator COMP2 is connected to the second positive input voltage, and the inverting input of comparator COMP2 is connected to the negative input voltage AVIN. The output of comparator COMP2 is electrically connected to the input of inverter INV2, and the output of inverter INV2 is electrically connected to the second terminal of the AND gate. The output of the AND gate outputs an enable signal VDDOVP.

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