CN219372282U - Auxiliary power supply circuit applied to high-voltage power device and related circuit - Google Patents

Abstract

The application discloses be applied to auxiliary power circuit of high-voltage power device belongs to high-voltage drive technical field, and this circuit includes: a single-tube forward power supply controlled by an open loop is adopted; a 555 timer circuit which is built by a 555 timer and has a soft start function and is used for providing PWM signals for the single-tube forward power supply; and the buffer module is connected with the 555 timer and the single-tube forward power supply and is used for buffering the PWM signals. Because the PWM signal of the single-tube forward power supply is provided by the 555 timer circuit, and the manufacturing cost of the 555 timer circuit is far lower than the manufacturing cost of the power supply control chip, the design cost required by the auxiliary power supply of the high-voltage power device can be obviously reduced through the arrangement structure. Correspondingly, the high-voltage driving circuit disclosed by the utility model has the beneficial effects.

Description

Auxiliary power supply circuit applied to high-voltage power device and related circuit

Technical Field

The utility model relates to the technical field of high-voltage driving, in particular to an auxiliary power supply circuit applied to a high-voltage power device and a high-voltage driving circuit.

Background

In a driving circuit including high-voltage power devices such as IGBTs (Insulated Gate Bipolar Transistor), insulated Gate Bipolar Transistors (IGBTs), silicon Carbide (SiC), and the like, it is generally necessary to isolate an auxiliary power supply to supply power to the driving circuit. Because the forward power supply has the advantages of simple structure, low manufacturing cost, and the like, the forward power supply is used for supplying power to a driving circuit containing high-voltage power devices at present. In a topology circuit of a forward power supply, a control module is usually required to send a PWM (Pulse Width Modulation ) signal with a fixed frequency and a fixed duty ratio to drive a switching tube, and meanwhile, the control module is combined with a direct current voltage output by a transformer in the forward power supply to supply power to a high-voltage power device driving circuit.

In order to avoid safety accidents in the operation scene of the permanent magnet synchronous motor, before the permanent magnet synchronous motor stops rotating, a driving circuit for supplying power to the permanent magnet synchronous motor needs to be ensured to at least maintain a power supply state to support the permanent magnet synchronous motor to enter a low-rotation-speed state, and a control module in a forward power supply needs to be capable of generating a continuous and stable PWM signal. In the prior art, in order to achieve the above objective, a control module in a forward power supply is generally required to be set as an expensive power supply control chip, which results in a high-voltage power device auxiliary power supply circuit requiring high design cost. Currently, there is no more effective solution to this technical problem.

Therefore, how to reduce the design cost required by the auxiliary power circuit of the high-voltage power device is a technical problem to be solved by those skilled in the art.

Disclosure of Invention

In view of the above, the present utility model is directed to an auxiliary power circuit and a high-voltage driving circuit for a high-voltage power device, so as to reduce the design cost required by the auxiliary power supply of the high-voltage power device. The specific scheme is as follows:

an auxiliary power circuit for a high voltage power device, comprising:

a single-tube forward power supply controlled by an open loop is adopted;

a 555 timer circuit which is built by a 555 timer and has a soft start function and is used for providing PWM signals for the single-tube forward power supply;

and the buffer module is connected with the 555 timer and the single-tube forward power supply and is used for buffering the PWM signals.

Preferably, the single-tube forward power supply includes: the DC power supply, the first capacitor, the second capacitor, the third capacitor, the first resistor, the first diode, the second diode, the third diode, the transformer and the first switch tube; the primary side of the transformer is provided with two windings, and the secondary side of the transformer is provided with one winding;

the positive pole and the negative pole of the DC power supply are respectively connected with the first end and the second end of the first capacitor, the second end of the first capacitor is grounded, the first end of the primary side first winding of the transformer is connected with the negative pole of the first diode, the positive pole of the first diode is grounded, a common end formed by the second end of the primary side first winding of the transformer and the first end of the primary side second winding of the transformer is connected with the first end of the first capacitor, the second end of the primary side second winding of the transformer is connected with the first end of the first switch tube, the second end of the first switch tube is grounded, the first end of the secondary side winding of the transformer is connected with the positive pole of the second diode, the negative pole of the second diode is respectively connected with the first end of the first resistor and the first end of the second capacitor, the second end of the first resistor is connected with the negative pole of the third diode, the second end of the second resistor is connected with the second end of the second capacitor and the second end of the second resistor, and the second end of the second resistor is connected with the second end of the second resistor;

correspondingly, the control end of the first switching tube is connected with the buffer module.

Preferably, the first switch tube is specifically an NMOS tube;

correspondingly, the G pole of the NMOS tube is the control end of the first switching tube, the D pole of the NMOS tube is the first end of the first switching tube, and the S pole of the NMOS tube is the second end of the first switching tube.

Preferably, the buffer module is specifically an operational amplifier.

Preferably, the 555 timer circuit includes: 555 timer, fourth diode, fifth diode, sixth diode, second resistor, third resistor, fourth resistor, fifth resistor, sixth resistor, fourth capacitor, fifth capacitor, sixth capacitor and second switch tube;

the first end of the fourth capacitor is connected with a power supply, the second end of the fourth capacitor is grounded, the first end of the fourth capacitor is connected with the first end of the second resistor, the first end of the third resistor, the first end of the fifth resistor, the first end of the sixth resistor and the RESET end of the 555 timer respectively, the first end of the second resistor is connected with the Vcc end of the timer, the second end of the second resistor is connected with the control end of the second switching tube and the first end of the fifth capacitor respectively, the second end of the fifth capacitor is grounded, the first end of the second switching tube is connected with the second end of the fifth resistor, the second end of the second switching tube is connected with the positive electrode of the sixth diode, the DISCH end of the 555 timer is connected with the negative electrode of the sixth diode, the second end of the fourth resistor is connected with the positive end of the fourth resistor and the second end of the 555 timer respectively, the second end of the fourth resistor is connected with the second end of the fourth resistor, the second end of the second switching tube is connected with the second end of the 555 timer, the second end of the fourth resistor is connected with the second end of the 555 timer respectively, and the second end of the fourth resistor is connected with the second end of the fourth resistor.

Preferably, the difference between the resistance values of the third resistor and the fifth resistor is greater than a preset threshold.

Preferably, the second switching tube is a PMOS tube;

correspondingly, the G pole of the PMOS tube is the control end of the second switching tube, the S pole of the PMOS tube is the first end of the second switching tube, and the D pole of the PMOS tube is the second end of the second switching tube.

Preferably, the method further comprises: a fifth diode;

the positive electrode of the fifth diode is connected with the THRES end of the 555 timer, and the negative electrode of the fifth diode is connected with the second end of the fourth resistor.

Preferably, the power supply voltage of the power supply is determined by the attribute characteristics of the 555 timer.

Correspondingly, the utility model also discloses a high-voltage driving circuit which comprises an auxiliary power circuit applied to the high-voltage power device.

Therefore, the auxiliary power supply circuit provided by the utility model is provided with the single-tube forward power supply adopting open loop control, the buffer module and the 555 timer circuit, wherein the 555 timer circuit is built by the 555 timer, has a soft start function, and can provide PWM signals for the single-tube forward power supply through the buffer module. Compared with the prior art, because the PWM signal of the single-tube forward power supply is provided by the 555 timer circuit, and the manufacturing cost of the 555 timer circuit is far lower than that of the power supply control chip, the design cost required by the auxiliary power supply of the high-voltage power device can be obviously reduced through the arrangement structure. Correspondingly, the high-voltage driving circuit disclosed by the utility model has the beneficial effects.

Drawings

In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present utility model, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.

Fig. 1 is a block diagram of an auxiliary power circuit applied to a high-voltage power device according to an embodiment of the present utility model;

fig. 2 is a block diagram of another auxiliary power circuit applied to a high-voltage power device according to an embodiment of the present utility model;

FIG. 3 is a block diagram of a single tube forward power supply in the prior art;

FIG. 4 is a block diagram of a 555 timer circuit according to an embodiment of the present utility model;

fig. 5 is a schematic diagram of the 555 timer circuit when outputting PWM signals during soft start.

Detailed Description

The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

Referring to fig. 1, fig. 1 is a block diagram of an auxiliary power circuit applied to a high-voltage power device according to an embodiment of the present utility model, where the circuit includes:

a single-tube forward power supply 11 controlled by an open loop is adopted;

a 555 timer circuit 13 which is built by a 555 timer and has a soft start function and is used for providing PWM signals for the single-tube forward power supply 11;

and the buffer module 12 is connected with the 555 timer and the single-tube forward power supply 11 and is used for buffering the PWM signals.

In the embodiment, an auxiliary power supply circuit applied to a high-voltage power device is provided, wherein a single-tube forward power supply 11, a buffer module 12 and a 555 timer circuit 13 which are controlled by open loop are arranged in the auxiliary power supply circuit; the 555 timer circuit 13 not only has a soft start function, but also the 555 timer in the 555 timer circuit 13 can provide PWM signals to the single-tube forward power supply 11 through the buffer module 12. When the 555 timer outputs the PWM signal, the buffer module 12 buffers the PWM signal, and transmits the buffered PWM signal to the single-tube forward power supply 11. In this embodiment, the buffer module 12 is used to make the PWM signal output by the 555 timer circuit 13 smoother and more stable.

It can be thought that when the single-tube forward power supply 11 receives the PWM signal sent by the 555 timer circuit 13 through the buffer module 12, the single-tube forward power supply 11 drives the switching tube under the action of the PWM signal, and simultaneously, the direct-current voltage output by the transformer in the single-tube forward power supply 11 is combined to supply power to the high-voltage power device. The high-voltage power device comprises, but is not limited to, power devices such as IGBT, siC and the like.

In this embodiment, the buffer module 12 may be any circuit structure capable of implementing a signal buffer function. Since the buffer module 12 is a functional module that is relatively common in practical applications, the configuration of the buffer module 12 is not specifically described herein. And 555 timer circuit 13 is a circuit module for providing PWM signals to single-tube forward power supply 11, which is composed of 555 timer and related peripheral circuits.

Obviously, because the core circuit of the 555 timer circuit 13 is constructed by the 555 timer with low price, compared with the prior art that a power control chip with high price can provide stable and reliable PWM signals for the forward power supply, the design cost required by the auxiliary power supply circuit of the high-voltage power device can be obviously reduced by the arrangement mode.

Therefore, the auxiliary power supply circuit provided by the utility model is provided with the single-tube forward power supply adopting open loop control, the buffer module and the 555 timer circuit, wherein the 555 timer circuit is built by the 555 timer, has a soft start function, and can provide PWM signals for the single-tube forward power supply through the buffer module. Compared with the prior art, because the PWM signal of the single-tube forward power supply is provided by the 555 timer circuit, and the manufacturing cost of the 555 timer circuit is far lower than that of the power supply control chip, the design cost required by the auxiliary power supply of the high-voltage power device can be obviously reduced through the arrangement structure.

Based on the above embodiments, the technical solution is further described and optimized in this embodiment, please refer to fig. 2, fig. 2 is a block diagram of another auxiliary power circuit applied to a high-voltage power device provided in the embodiment of the present utility model; as a preferred embodiment, the single-tube forward power supply 11 includes: the DC power supply, a first capacitor C1, a second capacitor C2, a third capacitor C3, a first resistor R1, a first diode D1, a second diode D2, a third diode D3, a transformer T and a first switch tube K1; the primary side of the transformer T is provided with two windings, and the secondary side of the transformer T is provided with one winding;

the positive electrode and the negative electrode of the DC power supply are respectively connected with the first end and the second end of a first capacitor C1, the second end of the first capacitor C1 is grounded, the first end of a primary winding of a transformer T is connected with the negative electrode of a first diode D1, the positive electrode of the first diode D1 is grounded, a public end formed by the second end of the primary winding of the transformer T and the first end of a secondary winding of the transformer T is connected with the first end of the first capacitor C1, the second end of the secondary winding of the transformer T is connected with the first end of a first switch tube K1, the second end of the first switch tube K1 is grounded, the first end of a secondary winding of the transformer T is connected with the positive electrode of a second diode D2, the negative electrode of the second diode D2 is respectively connected with the first end of a first resistor R1 and the first end of a second capacitor C2, the second end of the first resistor R1 is connected with the negative electrode of a third diode D3, the second end of the second capacitor C2 is connected with the second end of the third capacitor C3 and the second end of the third capacitor C3 is connected with the positive electrode of the third diode D1, and the second end of the second resistor C3 is connected with the second end of the second diode D2 is connected with the positive electrode of the third capacitor C1;

correspondingly, the control end of the first switching tube K1 is connected with the buffer module 12.

In this embodiment, a specific description is given of the arrangement structure of the single-tube forward power supply. Referring to fig. 3, fig. 3 is a block diagram of a single-tube forward power supply in the prior art. In this embodiment, in order to further simplify the circuit structure of the single-tube forward power supply, the inductance L and the freewheeling diode D13 on the secondary side of the transformer T in the single-tube forward power supply in the prior art are removed. In addition, because the driving power of the high-voltage power device is smaller and the load condition is fixed, in the embodiment, the single-tube forward power supply is set to be in open loop control, and the topological structure of the single-tube forward power supply is further simplified.

In the single-tube forward power supply shown in fig. 2, a primary side and a secondary side of a transformer T are electrically isolated, the primary side of the transformer T is a low-voltage side, and the secondary side of the transformer T is a high-voltage side. The primary side of the transformer T is provided with two windings, the windings connected with the first switching tube K1 transmit energy through the first switching tube K1, and the windings connected with the second diode D2 provide a reset channel for the transformer T during the turn-off period of the first switching tube K1. The transformer T rectifies an output voltage of the transformer T through the second diode D2, the second capacitor C2, and the third capacitor C3.

As a preferred embodiment, the first switching tube K1 is specifically an NMOS tube;

correspondingly, the G of the NMOS tube is the control end of the first switching tube K1, the D of the NMOS tube is the first end of the first switching tube K1, and the S of the NMOS tube is the second end of the first switching tube K1.

It can be understood that, because the on-resistance of the NMOS transistor is small and easy to manufacture, the first switching transistor K1 is set as the NMSO transistor in the present embodiment. In addition, in the embodiment, in order to further ensure the reliability of the NMOS tube in the working and running process, a parasitic diode is further arranged on the NMOS tube so as to prevent the NMOS tube from being burnt out when the NMOS tube suffers overvoltage.

Obviously, by the technical scheme provided by the embodiment, the circuit topology of the single-tube forward power supply can be further simplified, and the working performance of the single-tube forward power supply is more stable and reliable.

Based on the above embodiments, the present embodiment further describes and optimizes the technical solution, and as a preferred implementation, the buffer module 12 is specifically an op-amp.

Specifically, in this embodiment, the buffer module 12 is set as an operational amplifier, because the operational amplifier is low in price and manufacturing difficulty, and the space volume of the operational amplifier is small, when the buffer module 12 is set as the operational amplifier, the design cost of the auxiliary power circuit of the high-voltage power device can be further reduced, and the occupation amount of the auxiliary power circuit of the high-voltage power device to the space volume can be reduced.

Based on the above embodiments, the technical solution is further described and optimized in this embodiment, please refer to fig. 4, and fig. 4 is a block diagram of a 555 timer circuit provided in the embodiment of the present utility model. As a preferred embodiment, the 555 timer circuit comprises: 555 timer, fourth diode D4, fifth diode D5, sixth diode D6, second resistor R2, third resistor R3, fourth resistor R4, fifth resistor R5, sixth resistor R6, fourth capacitor C4, fifth capacitor C5, sixth capacitor C6 and second switch tube K2;

wherein the first end of the fourth capacitor C4 is connected to the power supply VCC, the second end of the fourth capacitor C4 is grounded, the first end of the fourth capacitor C4 is connected to the first end of the second resistor R2, the first end of the third resistor R3, the first end of the fifth resistor R5, the first end of the sixth resistor R6 and the RESET end of the 555 timer respectively, the first end of the second resistor R2 is connected to the Vcc end of the timer, the second end of the second resistor R2 is connected to the control end of the second switch tube K2 and the first end of the fifth capacitor C5 respectively, the second end of the fifth capacitor C5 is grounded, the first end of the second switch tube K2 is connected to the second end of the fifth resistor R5, the second end of the second switch tube K2 is connected with the positive pole of the sixth diode D6, the DISCH end of the 555 timer is respectively connected with the negative pole of the sixth diode D6, the second end of the third resistor R3, the first end of the fourth resistor R4 and the positive pole of the fourth diode D4, the second end of the fourth resistor R4 and the negative pole of the fourth diode D4 are respectively connected with the THRES end of the 555 timer, the second end of the fourth resistor R4 is respectively connected with the first end of the sixth capacitor C6 and the TRIG end of the 555 timer, the second end of the sixth capacitor C6 is grounded, and the output end of the 555 timer is respectively connected with the second end of the sixth resistor R6 and the buffer module.

In this embodiment, a 555 timer circuit is specifically described. The 555 timer circuit can output a PWM signal with a fixed frequency and a duty ratio, and the PWM signal output by the 555 timer circuit is buffered by the buffer module 12 and then sent to the single-tube forward power supply 11.

In practical application, the second switching tube K2 may be set as a triode, or the second switching tube K2 may be set as a PMOS tube. Because the coordination capability of the PMOS tube is better, and the PMOS tube is more convenient for integration in the processing technology. Therefore, in this embodiment, the second switching tube K2 is set as a PMOS tube; the G of the PMOS tube is the control end of the second switching tube K2, the S of the PMOS tube is the first end of the second switching tube K2, and the D of the PMOS tube is the second end of the second switching tube K2.

In this embodiment, in order to prevent the sixth capacitor C6 from flowing in the reverse direction during the discharging process, a fifth diode D5 may be further disposed in the 555 timer circuit; the positive electrode of the fifth diode D5 is connected to the THRES end of the 555 timer, and the negative electrode of the fifth diode D5 is connected to the second end of the fourth resistor R4.

It should be noted that, in order to ensure the operation performance of the 555 timer circuit, the supply voltage of the supply power VCC is determined by the attribute characteristics of the 555 timer. Meanwhile, in order to more obviously observe the soft start function of the 555 timer circuit, the resistance difference between the third resistor R3 and the fifth resistor R5 is larger than a preset threshold. In other words, the resistance of the third resistor R3 is much higher than the resistance of the fifth resistor R5, so as to select the resistances of the third resistor R3 and the fifth resistor R5, for example: the resistance of the third resistor R3 may be set to about 15 times that of the fifth resistor R5.

When the second switching tube K2 is set as a PMOS tube, the working principle of the 555 timer circuit is specifically as follows: when the 555 timer is electrified, the power supply VCC charges the fifth capacitor C5 through the second resistor R2, and the G pole voltage of the PMOS tube is increased from zero, and the S pole voltage of the PMOS tube is the voltage provided by the power supply VCC. In the charging process of the fifth capacitor C5, the voltage between the S pole and the G pole of the PMOS tube is slowly reduced, and as the voltage between the S pole and the G pole of the PMOS tube is gradually reduced, the impedance between the D pole and the S pole of the PMOS tube is gradually increased, and the current flowing through the PMOS tube is gradually reduced. When the voltage between the S pole and the G pole of the PMOS tube is smaller than the threshold voltage of the PMOS tube, the PMOS tube is turned off, and the current flowing through the PMOS tube is zero.

Since the resistance value of the fifth resistor R5 is far smaller than that of the third resistor R3, when the 555 timer is powered on, the power supply VCC charges the sixth capacitor C6 through the fifth resistor R5, the PMOS transistor, the sixth diode D6, and the fourth diode D4. When the voltage of the sixth capacitor C6 is greater than Vcc/3, the 555 timer will output low level, and the 555 timer will open the switch at the DISCH terminal, and the sixth capacitor C6 will start the discharging mode.

Specifically, the sixth capacitor C6 starts to discharge through the fifth diode D5, the fourth resistor R4 and the DISCH terminal of the 555 timer, and when the sixth capacitor C6 starts to discharge, the voltage of the sixth capacitor C6 starts to decrease. When the voltage of the sixth capacitor C6 is lower than Vcc/3, the 555 timer will output high level, and the switch at the disc end of the 555 timer will be turned off. When the switch at the DISCH end of the 555 timer is turned off, the sixth capacitor C6 starts to charge, and when the voltage of the sixth capacitor C6 rises to Vcc/3, the 555 timer outputs a low level again, and the above-mentioned process is repeated.

The charging current of the sixth capacitor C6 mainly flows through the fifth resistor R5, the PMOS transistor, the sixth diode D6 and the fourth diode D4 until the impedance value of the PMOS transistor is equal to the resistance value of the third resistor R3 in a period from the power-up time of the 555 timer, and the discharging current of the sixth capacitor C6 mainly flows through the DISCH terminals of the fifth diode D5, the fourth resistor R4 and the 555 timer. In the power-on process of the 555 timer, the impedance of the PMOS tube gradually becomes larger, the charging current of the sixth capacitor C6 gradually becomes smaller, and the charging time of the sixth capacitor C6 gradually increases. Since the impedance value of the discharge path of the sixth capacitor C6 is always constant, the discharge time of the sixth capacitor C6 is always constant.

It is conceivable that the charging time of the sixth capacitor C6 is prolonged, so that the time for the voltage of the sixth capacitor C6 to rise to Vcc/3 is gradually prolonged, and the time for the 555 timer to output the PWM signal at the high level is gradually increased, and in this case, the duty ratio of the PWM signal output by the 555 timer is increased. When the PMOS tube is turned off, the soft start of the 555 timer circuit is completely finished. At this time, the sixth capacitor C6 is charged through the third resistor R3 and the fourth diode D4, and the sixth capacitor C6 is discharged through the fifth diode D5, the fourth resistor R4 and the DISCH end of the 555 timer, the discharging loop of the sixth capacitor C6 remains unchanged, and the 555 timer outputs a PWM signal with a fixed duty ratio and frequency.

Referring to table 1, table 1 is a truth table of 555 timers.

TABLE 1

Referring to fig. 5, fig. 5 is a schematic diagram of the 555 timer circuit when outputting the PWM signal during soft start. As can be seen from fig. 5, when the charging time of the sixth capacitor C6 is gradually prolonged, the duty ratio of the PWM signal output by the 555 timer is also gradually increased.

Obviously, through the technical scheme that this embodiment provided, not only can make 555 timer circuit can be to single tube forward power supply output stable PWM signal, but also make 555 timer circuit have soft start function, just so can further improve high-voltage power device auxiliary power supply circuit's stability and reliability in operation.

Correspondingly, the embodiment of the utility model also discloses a high-voltage driving circuit which comprises an auxiliary power circuit applied to the high-voltage power device.

The high-voltage driving circuit provided by the embodiment of the utility model has the beneficial effects of the auxiliary power circuit applied to the high-voltage power device.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present utility model. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the utility model. Thus, the present utility model is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. An auxiliary power circuit for a high voltage power device, comprising:

a single-tube forward power supply controlled by an open loop is adopted;

a 555 timer circuit which is built by a 555 timer and has a soft start function and is used for providing PWM signals for the single-tube forward power supply;

and the buffer module is connected with the 555 timer and the single-tube forward power supply and is used for buffering the PWM signals.

2. The auxiliary power circuit of claim 1 wherein the single-tube forward power supply comprises: the DC power supply, the first capacitor, the second capacitor, the third capacitor, the first resistor, the first diode, the second diode, the third diode, the transformer and the first switch tube; the primary side of the transformer is provided with two windings, and the secondary side of the transformer is provided with one winding;

the positive pole and the negative pole of the DC power supply are respectively connected with the first end and the second end of the first capacitor, the second end of the first capacitor is grounded, the first end of the primary side first winding of the transformer is connected with the negative pole of the first diode, the positive pole of the first diode is grounded, a common end formed by the second end of the primary side first winding of the transformer and the first end of the primary side second winding of the transformer is connected with the first end of the first capacitor, the second end of the primary side second winding of the transformer is connected with the first end of the first switch tube, the second end of the first switch tube is grounded, the first end of the secondary side winding of the transformer is connected with the positive pole of the second diode, the negative pole of the second diode is respectively connected with the first end of the first resistor and the first end of the second capacitor, the second end of the first resistor is connected with the negative pole of the third diode, the second end of the second resistor is connected with the second end of the second capacitor and the second end of the second resistor, and the second end of the second resistor is connected with the second end of the second resistor;

correspondingly, the control end of the first switching tube is connected with the buffer module.

3. The auxiliary power circuit of claim 2, wherein the first switching tube is embodied as an NMOS tube;

correspondingly, the G pole of the NMOS tube is the control end of the first switching tube, the D pole of the NMOS tube is the first end of the first switching tube, and the S pole of the NMOS tube is the second end of the first switching tube.

4. Auxiliary power supply circuit according to claim 1, characterized in that the buffer module is in particular an op-amp.

5. The auxiliary power circuit of claim 1 wherein the 555 timer circuit comprises: 555 timer, fourth diode, fifth diode, sixth diode, second resistor, third resistor, fourth resistor, fifth resistor, sixth resistor, fourth capacitor, fifth capacitor, sixth capacitor and second switch tube;

the first end of the fourth capacitor is connected with a power supply, the second end of the fourth capacitor is grounded, the first end of the fourth capacitor is connected with the first end of the second resistor, the first end of the third resistor, the first end of the fifth resistor, the first end of the sixth resistor and the RESET end of the 555 timer respectively, the first end of the second resistor is connected with the Vcc end of the timer, the second end of the second resistor is connected with the control end of the second switching tube and the first end of the fifth capacitor respectively, the second end of the fifth capacitor is grounded, the first end of the second switching tube is connected with the second end of the fifth resistor, the second end of the second switching tube is connected with the positive electrode of the sixth diode, the DISCH end of the 555 timer is connected with the negative electrode of the sixth diode, the second end of the fourth resistor is connected with the positive end of the fourth resistor and the second end of the 555 timer respectively, the second end of the fourth resistor is connected with the second end of the fourth resistor, the second end of the second switching tube is connected with the second end of the 555 timer, the second end of the fourth resistor is connected with the second end of the 555 timer respectively, and the second end of the fourth resistor is connected with the second end of the fourth resistor.

6. The auxiliary power circuit of claim 5, wherein a difference in resistance between the third resistor and the fifth resistor is greater than a preset threshold.

7. The auxiliary power circuit of claim 5, wherein the second switching tube is embodied as a PMOS tube;

correspondingly, the G pole of the PMOS tube is the control end of the second switching tube, the S pole of the PMOS tube is the first end of the second switching tube, and the D pole of the PMOS tube is the second end of the second switching tube.

8. The auxiliary power circuit of claim 5, further comprising: a fifth diode;

the positive electrode of the fifth diode is connected with the THRES end of the 555 timer, and the negative electrode of the fifth diode is connected with the second end of the fourth resistor.

9. The auxiliary power circuit of claim 5 wherein the supply voltage of the supply is determined by a characteristic feature of the 555 timer.

10. A high voltage driving circuit comprising an auxiliary power supply circuit as claimed in any one of claims 1 to 9 for use in a high voltage power device.