A negative pressure generating circuit

Abstract

The application provides a negative pressure generation circuit, belonging to the technical field of negative pressure generation. The negative pressure generation circuit is used for providing negative pressure for the gate of a MOS tube, and comprises a driving module, a negative pressure generation module, a negative pressure adjustment module, a temperature detection module and a clamping module. The input end of the driving module is used for receiving a PWM signal, the output end of the driving module is connected with the input end of the negative pressure generation module, the output end of the negative pressure generation module is used for outputting negative pressure, the first end of the negative pressure adjustment module is connected with the output end of the driving module, the second end of the negative pressure adjustment module is connected with the output end of the negative pressure generation module, the control end of the negative pressure adjustment module is connected with the temperature detection module, the temperature detection module is configured to detect the surface temperature of the MOS tube, and the output end of the negative pressure generation module is connected with the clamping module. The application can adjust the output negative pressure based on the temperature of the MOS tube.

Description

Technical Field

[0001] This application relates to the field of negative pressure generation technology, and in particular to a negative pressure generation circuit. Background Technology

[0002] In the field of power electronics, metal-oxide-semiconductor field-effect transistors (MOS transistors) are widely used in high-frequency switching scenarios such as motor drives, switching power supplies, and inverters due to their advantages such as fast switching speed, high input impedance, and low drive power.

[0003] Traditional MOSFET negative voltage drive circuits mostly use a fixed negative voltage power supply. However, temperature can affect the electrical performance of MOSFETs. Therefore, a negative voltage generation circuit is needed to solve the problem that the negative voltage of MOSFETs does not meet the requirements due to temperature changes. Utility Model Content

[0004] This application provides a negative voltage generation circuit to solve the problem that the negative voltage of the MOSFET does not meet the usage requirements due to temperature changes.

[0005] This application provides a negative voltage generation circuit to provide a negative voltage to the gate of a MOSFET, including: a driving module, a negative voltage generation module, a negative voltage adjustment module, a temperature detection module, and a clamping module;

[0006] The input terminal of the drive module is used to receive PWM signals, and the output terminal of the drive module is connected to the input terminal of the negative pressure generation module; the output terminal of the negative pressure generation module is used to output negative pressure.

[0007] The first end of the negative pressure adjustment module is connected to the output end of the drive module, the second end of the negative pressure adjustment module is connected to the output end of the negative pressure generation module, and the control end of the negative pressure adjustment module is connected to the temperature detection module. The temperature detection module is configured to detect the surface temperature of the MOSFET.

[0008] The output of the negative pressure generation module is connected to the clamping module.

[0009] In one exemplary embodiment of this application, the driving module includes: resistor R1, transistor Q1, transistor Q2, resistor R4, and capacitor C1;

[0010] The first end of resistor R1 is used to receive PWM signals, and the second end of resistor R1 is connected to the base of transistor Q1, the base of transistor Q2, and the first end of resistor R4 respectively.

[0011] The collector of transistor Q1 is connected to the power supply; the emitter of transistor Q1 is connected to the emitter of transistor Q2.

[0012] The collector of transistor Q2 and the second terminal of resistor R4 are both grounded;

[0013] The first terminal of capacitor C1 is connected to the collector of transistor Q1, and the second terminal of capacitor C1 is grounded.

[0014] The emitter of transistor Q1 is connected to the input terminal of the negative voltage generation module.

[0015] In one exemplary embodiment of this application, the driving module includes: resistor R1, transistor Q1, transistor Q2, resistor R4, and capacitor C1;

[0016] The first end of resistor R1 is used to receive PWM signals, and the second end of resistor R1 is connected to the base of transistor Q1, the base of transistor Q2, and the first end of resistor R4 respectively.

[0017] The collector of transistor Q1 is connected to the power supply; the emitter of transistor Q1 is connected to the emitter of transistor Q2.

[0018] The collector of transistor Q2 and the second terminal of resistor R4 are both grounded;

[0019] The first terminal of capacitor C1 is connected to the collector of transistor Q1, and the second terminal of capacitor C1 is grounded.

[0020] The emitter of transistor Q1 is connected to the input terminal of the negative voltage generation module.

[0021] In one exemplary embodiment of this application, the negative pressure adjustment module includes: a temperature judgment unit and a negative pressure adjustment unit;

[0022] The input terminal of the temperature judgment unit is connected to the temperature detection module, the output terminal of the temperature judgment unit is connected to the control terminal of the negative pressure adjustment unit, the first terminal of the negative pressure adjustment unit is connected to the output terminal of the drive module, and the second terminal of the negative pressure adjustment unit is connected to the output terminal of the negative pressure generation module.

[0023] In one exemplary embodiment of this application, the temperature determination unit includes: resistor R8, resistor R9, capacitor C4, capacitor C5, operational amplifier U2, voltage adjustment chip U3, and AND gate U4;

[0024] The input terminal of the voltage regulator chip U3 is connected to the power supply;

[0025] The input terminal of voltage regulator chip U3 is connected to the ground terminal of voltage regulator chip U3 through capacitor C5;

[0026] The output of voltage regulator chip U3 is connected to the non-inverting input of operational amplifier U2 through resistor R9;

[0027] The output terminal of voltage regulator chip U3 is connected to the ground terminal of voltage regulator chip U3 through capacitor C4; the ground terminal of voltage regulator chip U3 is grounded.

[0028] The first end of resistor R8 is connected to the temperature detection module, and the second end of resistor R8 is connected to the inverting input of operational amplifier U2.

[0029] Both the first input terminal and the second input terminal of AND gate U4 are connected to the output terminal of operational amplifier U2;

[0030] The output of AND gate U4 is connected to the control terminal of the negative pressure adjustment unit.

[0031] In one exemplary embodiment of this application, the negative pressure adjustment unit includes: resistor R6, resistor R7, transistor Q3, relay P1, diode Z1, and diode Z3;

[0032] The first end of resistor R6 is connected to the output of AND gate U4, the second end of resistor R6 is connected to the base of transistor Q3, the second end of resistor R6 is grounded through resistor R7, and the collector of transistor Q3 is grounded.

[0033] The first input terminal of relay P1 is connected to the power supply, and the second input terminal of relay P1 is connected to the emitter of transistor Q3.

[0034] The common terminal of relay P1 is connected to the output terminal of the negative pressure generation module;

[0035] The first output terminal of relay P1 is connected to the positive terminal of diode Z1, and the negative terminal of diode Z1 is connected to the output terminal of the drive module.

[0036] The second output terminal of relay P1 is connected to the positive terminal of diode Z3, and the negative terminal of diode Z3 is connected to the output terminal of the drive module.

[0037] In one exemplary embodiment of this application, the temperature detection module includes: a thermistor RT1 and a resistor R5;

[0038] The first terminal of the thermistor RT1 is connected to the power supply.

[0039] The second terminal of the thermistor RT1 is grounded through resistor R5;

[0040] The second terminal of the thermistor RT1 is connected to the control terminal of the negative voltage adjustment module.

[0041] In one exemplary embodiment of this application, the clamping module includes: a resistor R3 and a diode Z2;

[0042] The first end of resistor R3 is connected to the second end of capacitor C2, the second end of resistor R3 is connected to the positive terminal of diode Z2, and the negative terminal of diode Z2 is grounded.

[0043] The beneficial effects of the negative pressure generating circuit provided in this application embodiment are as follows:

[0044] The negative voltage generation circuit of this application incorporates a temperature detection module, which monitors the surface temperature of the MOSFET in real time and converts the temperature information into an electrical signal (such as a voltage value) for use by the negative voltage adjustment module. The negative voltage adjustment module dynamically adjusts the negative voltage based on the temperature information fed back by the temperature detection module. When the temperature rises, the performance of the MOSFET changes, and the required voltage decreases with increasing temperature. In this case, the negative voltage adjustment module can correspondingly reduce the output negative voltage, ensuring that the negative voltage provided to the MOSFET gate always meets the usage requirements under various temperature conditions, effectively improving the circuit's adaptability and stability in temperature-changing environments. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a schematic diagram of the structure of the first negative pressure generating circuit provided in the embodiments of this application;

[0047] Figure 2 This is a schematic diagram of the structure of the second negative pressure generating circuit provided in the embodiments of this application. Detailed Implementation

[0048] To enable those skilled in the art to better understand this solution, the technical solutions in the embodiments of this solution will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this solution, not all of them. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this solution.

[0049] The term "comprising" and any other variations thereof in the specification, claims, and accompanying drawings of this invention mean "including but not limited to," and are intended to cover a non-exclusive inclusion, not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order.

[0050] The implementation of this application will be described in detail below with reference to the specific accompanying drawings:

[0051] Figure 1 This is a schematic diagram of the structure of a first negative pressure generating circuit provided in an embodiment of this application. (Refer to...) Figure 1The negative voltage generation circuit is used to provide a negative voltage to the gate of the MOSFET. The circuit includes: a driving module 10, a negative voltage generation module 11, a negative voltage adjustment module 12, a temperature detection module 13, and a clamping module 14.

[0052] The input terminal of the drive module 10 is used to receive PWM signals, and the output terminal of the drive module 10 is connected to the input terminal of the negative pressure generation module 11; the output terminal of the negative pressure generation module 11 is used to output negative pressure.

[0053] The first end of the negative pressure adjustment module 12 is connected to the output end of the drive module 10, the second end of the negative pressure adjustment module 12 is connected to the output end of the negative pressure generation module 11, and the control end of the negative pressure adjustment module 12 is connected to the temperature detection module 13. The temperature detection module 13 is configured to detect the surface temperature of the MOSFET.

[0054] The output of the negative pressure generation module 11 is connected to the clamping module 14.

[0055] In this embodiment, the drive module 10 can receive PWM signals and output drive signals. The drive module 10 is configured to enhance signal driving capability to ensure rapid charging and discharging of capacitive loads. The negative voltage generation module 11 can generate negative voltage, which can enhance the turn-off capability of the MOSFET and reduce switching losses.

[0056] In this embodiment, the negative voltage adjustment module 12 is configured to dynamically adjust the negative voltage based on the MOSFET temperature. As the temperature rises, the performance of the MOSFET changes with the temperature. In this scenario, the voltage required by the MOSFET decreases as the temperature rises. Therefore, in this application, the output negative voltage can be determined based on the MOSFET temperature. The temperature detection module 13 can monitor the MOSFET surface temperature in real time and convert it into an electrical signal (such as a voltage value) for use by the negative voltage adjustment module 12. The clamping module 14 is configured to limit the maximum value (absolute value) of the negative voltage to prevent damage to the MOSFET or other components due to excessively low voltage.

[0057] As can be seen from the above, the negative voltage generation circuit of this application is equipped with a temperature detection module 13, which can monitor the surface temperature of the MOSFET in real time and convert the temperature information into an electrical signal (such as a voltage value) for use by the negative voltage adjustment module 12. The negative voltage adjustment module 12 dynamically adjusts the magnitude of the negative voltage based on the temperature information fed back by the temperature detection module 13. When the temperature rises, the performance of the MOSFET changes, and the required voltage decreases as the temperature rises. At this time, the negative voltage adjustment module 12 can correspondingly reduce the magnitude of the output negative voltage, ensuring that the negative voltage provided to the gate of the MOSFET always meets the usage requirements under various temperature conditions, effectively improving the adaptability and stability of the circuit in temperature-changing environments.

[0058] Figure 2This is a schematic diagram of the structure of the second negative pressure generating circuit provided in the embodiments of this application. For example... Figure 2 In one embodiment of this application, the driving module 10 includes: resistor R1, transistor Q1, transistor Q2, resistor R4, and capacitor C1;

[0059] The first end of resistor R1 is used to receive PWM signals, and the second end of resistor R1 is connected to the base of transistor Q1, the base of transistor Q2, and the first end of resistor R4 respectively.

[0060] The collector of transistor Q1 is connected to the power supply; the emitter of transistor Q1 is connected to the emitter of transistor Q2.

[0061] The collector of transistor Q2 and the second terminal of resistor R4 are both grounded;

[0062] The first terminal of capacitor C1 is connected to the collector of transistor Q1, and the second terminal of capacitor C1 is grounded.

[0063] The emitter of transistor Q1 is connected to the input terminal of negative voltage generation module 11.

[0064] In this embodiment, when the PWM signal is high, transistor Q1 is turned on, the emitter output is approximately Vcc, and transistor Q2 is turned off. When the PWM signal is low, transistor Q2 is turned on, the emitter output is approximately GND, and transistor Q1 is turned off. When transistors Q1 and Q2 are turned on alternately, the output impedance is low (only the internal resistance of the conducting transistor), which can provide a large current for rapid charging and discharging, thereby improving the driving capability.

[0065] As can be seen from the above, the low output impedance (only the internal resistance of the conducting transistors Q1 and Q2 in the driving module 10) of this application can provide a large current, which can quickly charge and discharge the capacitive load in the subsequent circuit, thereby significantly improving the driving capability and ensuring that the MOSFET can quickly respond to the PWM signal and achieve precise switching action.

[0066] In one embodiment of this application, the negative pressure generating module 11 includes: a capacitor C2;

[0067] The first end of capacitor C2 is connected to the output end of driver module 10;

[0068] The second terminal of capacitor C2 is used to output negative voltage.

[0069] In this embodiment, when the PWM signal is high, Q1 is turned on and Q2 is turned off, resulting in a high-level output drive waveform. The amplitude of the high level is VCC minus the voltage drop of transistor Q1. At this time, capacitor C2 is charged, and the negative voltage generation module outputs a positive voltage. In this embodiment, the negative voltage generation module only outputs a negative voltage when the MOSFET needs to be turned off, depending on whether the PWM signal level is high or low. Only when the MOSFET needs to be turned off will the PWM signal output a low level. At this time, Q1 is turned off and Q2 is turned on, and the drive current flow direction is reversed. At this time, the polarity of capacitor C2 is reversed, and it is converted to a discharge state, so a negative voltage can be output.

[0070] In this embodiment, the negative pressure generation module 11 may further include a resistor R2 for protection circuit. The first end of the resistor R2 is connected to the output terminal of the drive module 10, and the second end of the resistor R2 is connected to the first end of the capacitor C2.

[0071] As can be seen from the above, this application simplifies the complex negative pressure generation circuit to capacitor C2, reducing the difficulty of circuit design and the number of components used, thereby reducing the manufacturing cost of the circuit, which has a high cost performance and is suitable for large-scale production and application.

[0072] In one embodiment of this application, the negative pressure adjustment module 12 includes: a temperature judgment unit and a negative pressure adjustment unit;

[0073] The input terminal of the temperature judgment unit is connected to the temperature detection module 13, the output terminal of the temperature judgment unit is connected to the control terminal of the negative pressure adjustment unit, the first terminal of the negative pressure adjustment unit is connected to the output terminal of the drive module 10, and the second terminal of the negative pressure adjustment unit is connected to the output terminal of the negative pressure generation module 11.

[0074] In this embodiment, the temperature judgment unit is configured to detect the surface temperature of the MOS transistor and transmit the temperature information to the negative voltage adjustment unit. The negative voltage adjustment unit determines whether to perform an adjustment action based on whether the temperature sent by the temperature judgment unit exceeds a preset temperature. Specifically, the temperature judgment unit includes: resistor R8, resistor R9, capacitor C4, capacitor C5, operational amplifier U2, voltage adjustment chip U3, and AND gate U4.

[0075] The input terminal of the voltage regulator chip U3 is connected to the power supply;

[0076] The input terminal of voltage regulator chip U3 is connected to the ground terminal of voltage regulator chip U3 through capacitor C5;

[0077] The output of voltage regulator chip U3 is connected to the non-inverting input of operational amplifier U2 through resistor R9;

[0078] The output terminal of voltage regulator chip U3 is connected to the ground terminal of voltage regulator chip U3 through capacitor C4; the ground terminal of voltage regulator chip U3 is grounded.

[0079] The first end of resistor R8 is connected to temperature detection module 13, and the second end of resistor R8 is connected to the inverting input of operational amplifier U2.

[0080] Both the first input terminal and the second input terminal of AND gate U4 are connected to the output terminal of operational amplifier U2;

[0081] The output of AND gate U4 is connected to the control terminal of the negative pressure adjustment unit.

[0082] In this embodiment, the voltage adjustment chip U3 can adjust the output voltage to a preset voltage, depending on the capacitance values ​​of capacitors C4 and C5 and the chip model. The output voltage of the voltage adjustment chip U3 is used as a reference temperature signal. When the temperature signal output by the temperature detection module 13 is higher than the reference temperature signal, the operational amplifier U2 outputs a low level, and both input terminals of the AND gate U4 are at a low level. Therefore, the AND gate U4 outputs a low level.

[0083] In this embodiment, when the temperature signal output by the temperature detection module 13 is lower than the reference temperature signal, the operational amplifier U2 outputs a high level, and both input terminals of the AND gate U4 are at a high level. At this time, when the AND gate U4 outputs a high level, the base of the transistor Q3 is at a high level. Since the transistor Q3 is a PNP transistor, when the base is at a high level, the transistor Q3 is cut off, there is no current in the coil of the relay P1, and the switch cannot be controlled to close.

[0084] When the signal detected by the aforementioned temperature detection module 13 is higher than the reference temperature signal, the AND gate U4 outputs a low level. At this time, the base of transistor Q3 is at a low level, transistor Q3 conducts, the coil of relay P1 is energized, and the switch of relay P1 is closed. This controls the type or parameters of the diode connected in the circuit, which essentially controls different voltage regulation values, thereby controlling the negative voltage value of the output negative voltage. Specifically, in one embodiment of this application, the negative voltage adjustment unit includes: resistor R6, resistor R7, transistor Q3, relay P1, diode Z1, and diode Z3.

[0085] The first end of resistor R6 is connected to the output of AND gate U4, the second end of resistor R6 is connected to the base of transistor Q3, the second end of resistor R6 is grounded through resistor R7, and the collector of transistor Q3 is grounded.

[0086] The first input terminal of relay P1 is connected to the power supply, and the second input terminal of relay P1 is connected to the emitter of transistor Q3.

[0087] The common terminal of relay P1 is connected to the output terminal of negative pressure generation module 11;

[0088] The first output terminal of relay P1 is connected to the positive terminal of diode Z1, and the negative terminal of diode Z1 is connected to the output terminal of drive module 10.

[0089] The second output terminal of relay P1 is connected to the positive terminal of diode Z3, and the negative terminal of diode Z3 is connected to the output terminal of drive module 10.

[0090] In this embodiment, diode Z1 can clamp the low-level drive to the negative value of its own regulated voltage minus the voltage drop of transistor Q2, and diode Z3 can do the same. Since diodes Z1 and Z3 have different regulated voltages, different negative voltages can be controlled to output. In this embodiment, the relationship between the regulated voltages of diodes Z1 and Z3 should be based on the initial state of relay P1. The regulated voltage of the diode corresponding to the initial connection state of relay P1 should be greater than the regulated voltage of the diode after the temperature exceeds the limit, so as to adjust the negative voltage output after the temperature exceeds the limit.

[0091] As can be seen from the above, the voltage adjustment chip U3 can adjust the output voltage to a preset stable voltage to provide a reference for temperature comparison. When the signal detected by the temperature detection module 13 is higher than the reference temperature signal, the AND gate U4 outputs a low level, the transistor Q3 conducts, the relay P1 coil is energized, and the switch is energized, thereby controlling the output negative voltage value. The method of adjusting the negative voltage by switching different circuit paths through the relay switch has great flexibility and adjustability. It can quickly and accurately adjust the negative voltage output according to different temperature conditions to meet the needs of the MOSFET under different working conditions.

[0092] In one embodiment of this application, the temperature detection module 13 includes: a thermistor RT1 and a resistor R5;

[0093] The first terminal of the thermistor RT1 is connected to the power supply.

[0094] The second terminal of the thermistor RT1 is grounded through resistor R5;

[0095] The second terminal of the thermistor RT1 is connected to the control terminal of the negative voltage adjustment module 12.

[0096] In one embodiment of this application, the clamping module 14 includes: a resistor R3 and a diode Z2;

[0097] The first end of resistor R3 is connected to the second end of capacitor C2, the second end of resistor R3 is connected to the positive terminal of diode Z2, and the negative terminal of diode Z2 is grounded.

[0098] In this embodiment, the thermistor RT1 is a negative temperature coefficient resistor, whose resistance decreases as the temperature increases. That is, when the surface temperature of the MOSFET increases, the resistance of the thermistor RT1 decreases, resulting in a smaller voltage drop. The resistance of resistor R5 remains unchanged, but the corresponding voltage drop increases. Therefore, as the temperature increases, the output voltage of the temperature detection module 13 increases. Diode Z2 can clamp the lower limit of the negative voltage, ensuring the operating range of the driving negative voltage. For example, it can output a negative voltage of -3.9 volts when the temperature is normal, and a negative voltage of -5.1 volts when the temperature exceeds the limit.

[0099] As can be seen from the above, the temperature detection module 13 of this application consists of only two components: a thermistor RT1 and a resistor R5. Its structure is simple and easy to implement. Compared to complex temperature detection circuits, this simple structure not only reduces the difficulty of circuit design but also reduces the number of components used, thereby lowering the manufacturing cost and offering high cost-effectiveness, making it suitable for mass production and application. During circuit operation, the clamping characteristic of diode Z2 prevents excessively low negative voltage, ensuring that the driving negative voltage is always within a reasonable operating range. This helps protect circuit components such as MOSFETs, preventing the MOSFETs from failing to turn off properly or experiencing other abnormal operating states due to excessively low negative voltage, thus improving the stability and reliability of the entire circuit system.

[0100] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A negative voltage generating circuit, characterized in that, The system provides a negative voltage to the gate of the MOSFET, including: a driving module, a negative voltage generation module, a negative voltage adjustment module, a temperature detection module, and a clamping module; The input terminal of the drive module is used to receive PWM signals, and the output terminal of the drive module is connected to the input terminal of the negative pressure generation module; the output terminal of the negative pressure generation module is used to output negative pressure. The first end of the negative pressure adjustment module is connected to the output end of the drive module, the second end of the negative pressure adjustment module is connected to the output end of the negative pressure generation module, and the control end of the negative pressure adjustment module is connected to the temperature detection module. The temperature detection module is configured to detect the surface temperature of the MOS transistor. The output of the negative pressure generation module is connected to the clamping module.

2. The negative voltage generating circuit as described in claim 1, characterized in that, The driving module includes: resistor R1, transistor Q1, transistor Q2, resistor R4, and capacitor C1; The first end of the resistor R1 is used to receive the PWM signal, and the second end of the resistor R1 is connected to the base of the transistor Q1, the base of the transistor Q2, and the first end of the resistor R4, respectively. The collector of transistor Q1 is connected to the power supply; the emitter of transistor Q1 is connected to the emitter of transistor Q2. The collector of the transistor Q2 and the second terminal of the resistor R4 are both grounded; The first terminal of capacitor C1 is connected to the collector of transistor Q1, and the second terminal of capacitor C1 is grounded. The emitter of the transistor Q1 is connected to the input terminal of the negative pressure generation module.

3. The negative voltage generating circuit as described in claim 1, characterized in that, The negative pressure generating module includes: capacitor C2; The first end of the capacitor C2 is connected to the output end of the drive module; The second terminal of capacitor C2 is used to output negative voltage.

4. The negative voltage generating circuit as described in claim 1, characterized in that, The negative pressure adjustment module includes: a temperature judgment unit and a negative pressure adjustment unit; The input terminal of the temperature judgment unit is connected to the temperature detection module, the output terminal of the temperature judgment unit is connected to the control terminal of the negative pressure adjustment unit, the first terminal of the negative pressure adjustment unit is connected to the output terminal of the drive module, and the second terminal of the negative pressure adjustment unit is connected to the output terminal of the negative pressure generation module.

5. The negative voltage generating circuit as described in claim 4, characterized in that, The temperature judgment unit includes: resistor R8, resistor R9, capacitor C4, capacitor C5, operational amplifier U2, voltage adjustment chip U3, and AND gate U4; The input terminal of the voltage adjustment chip U3 is connected to the power supply; The input terminal of the voltage adjustment chip U3 is connected to the ground terminal of the voltage adjustment chip U3 through the capacitor C5; The output terminal of the voltage adjustment chip U3 is connected to the non-inverting input terminal of the operational amplifier U2 through the resistor R9; The output terminal of the voltage adjustment chip U3 is connected to the ground terminal of the voltage adjustment chip U3 through the capacitor C4; the ground terminal of the voltage adjustment chip U3 is grounded. The first end of the resistor R8 is connected to the temperature detection module, and the second end of the resistor R8 is connected to the inverting input terminal of the operational amplifier U2. The first input terminal and the second input terminal of AND gate U4 are both connected to the output terminal of operational amplifier U2; The output terminal of AND gate U4 is connected to the control terminal of the negative pressure adjustment unit.

6. The negative voltage generating circuit as described in claim 5, characterized in that, The negative pressure adjustment unit includes: resistor R6, resistor R7, transistor Q3, relay P1, diode Z1, and diode Z3; The first end of the resistor R6 is connected to the output terminal of the AND gate U4, the second end of the resistor R6 is connected to the base of the transistor Q3, the second end of the resistor R6 is grounded through the resistor R7, and the collector of the transistor Q3 is grounded. The first input terminal of the relay P1 is connected to the power supply, and the second input terminal of the relay P1 is connected to the emitter of the transistor Q3. The common terminal of the relay P1 is connected to the output terminal of the negative pressure generation module; The first output terminal of the relay P1 is connected to the positive terminal of the diode Z1, and the negative terminal of the diode Z1 is connected to the output terminal of the drive module. The second output terminal of the relay P1 is connected to the positive terminal of the diode Z3, and the negative terminal of the diode Z3 is connected to the output terminal of the drive module.

7. The negative voltage generating circuit as described in claim 1, characterized in that, The temperature detection module includes: a thermistor RT1 and a resistor R5; The first terminal of the thermistor RT1 is connected to a power supply. The second terminal of the thermistor RT1 is grounded through the resistor R5; The second terminal of the thermistor RT1 is connected to the control terminal of the negative pressure adjustment module.

8. A negative voltage generating circuit as described in claim 3, characterized in that, The clamping module includes: resistor R3 and diode Z2; The first end of the resistor R3 is connected to the second end of the capacitor C2, the second end of the resistor R3 is connected to the positive terminal of the diode Z2, and the negative terminal of the diode Z2 is grounded.

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