A driving method and a driving system of a power switch tube

Abstract

The application relates to the technical field of power switches, and discloses a driving method and a driving system of a power switch tube, wherein the driving method of the power switch tube is used for driving a circuit, and the method comprises the following steps: S1, a driving transformer is controlled to output a pre-charging driving voltage, the amplitude of the pre-charging driving voltage is configured to be able to drive a reverse bias voltage generating circuit to work to establish a reverse bias voltage, and the effective driving voltage applied to the control end of the power switch tube is kept below the conduction threshold voltage of the power switch tube; S2, the pre-charging driving voltage is maintained until a preset reverse bias voltage establishment condition is met; and S3, the driving transformer is controlled to switch to output a working driving voltage, and the working driving voltage is configured to be higher than the sum of the conduction threshold voltage of the power switch tube and the reverse bias voltage, so as to drive the power switch tube to be turned on. The application can reduce the risk of mis-conduction of the power switch tube in the starting stage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power switch, in particular to a driving method and system of power switch tube. BACKGROUND

[0002] In the power switch technology, double-ended topological structures such as full-bridge and half-bridge are widely used, and the upper and lower bridge arms are usually driven by an isolation transformer. The MCU sends two complementary PWM driving waveforms, which drive the upper bridge arm power switch tube and the lower bridge arm power switch tube after isolation by the isolation transformer. The power switch tube is usually a MOSFET. When one side of the bridge arm MOSFET is turned on, the drain voltage of the other side of the bridge arm MOSFET rises rapidly. Due to the existence of the MOSFET parasitic capacitor Cgd, its gate will couple a voltage spike, which may cause the MOSFET to mis-conduct, and further cause the upper and lower bridge arms to be directly connected and damaged. Usually, the gate drive voltage of the MOSFET needs to be pulled to a certain negative voltage during the off period of the MOSFET, so as to ensure that even if the gate is coupled to an interference voltage, the gate voltage can still be maintained below the conduction threshold.

[0003] In the prior art, a reverse bias voltage generation circuit is usually used, such as a charge pump circuit composed of a diode, a voltage stabilizing tube and a capacitor, which clamps the gate of the power switch tube at a reverse bias voltage during the off period of the switch tube. However, the negative voltage clamping scheme based on the charge pump principle mainly relies on the matching of the RC time constant and the circuit switching frequency to establish and maintain the negative voltage, which is a passive working mechanism relying on the inherent parameters of the circuit. This design can work well in the scene where the circuit parameters are fixed and the working conditions are stable, but in the system startup stage, the working condition requiring frequency adjustment or the scene of dynamic load change, due to the limitation of the inherent response characteristics of the circuit, the timing and amplitude of the negative voltage establishment are difficult to adjust in real time according to the actual working condition, and the situation that the negative voltage has not been stabilized before entering the normal driving stage may occur, which still has the risk of direct connection. SUMMARY

[0004] In order to improve the power tube mis-conduction problem caused by the traditional driving circuit, the present application provides a driving method and system of power switch tube.

[0005] In the first aspect, the present application provides a driving method of power switch tube, which adopts the following technical scheme:

[0006] The application relates to a driving method of a power switch tube, which is applied to a driving circuit, the driving circuit comprising a driving transformer for driving the power switch tube and a reverse bias voltage generation circuit connected between the secondary side of the driving transformer and the power switch tube, and the method comprises the following steps: S1, a pre-charging driving voltage is output by controlling the driving transformer, the amplitude of the pre-charging driving voltage is configured to be able to drive the reverse bias voltage generation circuit to work so as to establish a reverse bias voltage, and the effective driving voltage applied to the control end of the power switch tube is kept below the conduction threshold voltage of the power switch tube; S2, the pre-charging driving voltage is maintained until a preset reverse bias voltage establishment condition is met; and S3, the driving transformer is controlled to switch to output a working driving voltage, and the working driving voltage is configured to be higher than the sum of the conduction threshold voltage of the power switch tube and the reverse bias voltage, so as to drive the power switch tube to be turned on.

[0007] By adopting the technical scheme, the pre-charging driving voltage lower than the conduction threshold voltage of the power switch tube is first output, the reverse bias voltage generation circuit is driven to establish the reverse bias voltage under the premise that the power switch tube is not turned on, the working driving voltage is switched to after the establishment condition is met, the active control logic of 'first establishing the reverse bias voltage and then turning on the switch' is realized, the problem of the lag of the reverse bias voltage establishment in the starting, frequency conversion or dynamic load scene is improved compared with the traditional passive negative voltage generation scheme, the gate of the power switch tube is ensured to be in the safe reverse bias state from the first normal driving period, and the risk of the upper and lower bridge arms being short-circuited is reduced.

[0008] Optionally, the determination step until the preset reverse bias voltage establishment condition is met comprises: starting a timer or a counter to count the duration or the number of switching periods of the output pre-charging driving voltage; if the duration reaches a preset first time length threshold value or the number of periods reaches a preset first period number threshold value, it is determined that the reverse bias voltage establishment condition is met.

[0009] By adopting the technical scheme, the timing determination logic is simple and direct, does not need an additional voltage acquisition circuit, can be realized by relying on the timer or the counter, and the system complexity and cost are reduced. The preset time length or period threshold value is verified by experiments, can ensure that the reverse bias voltage generation circuit fully completes the charging, meets the reliability requirement of most conventional application scenes, and is suitable for the use environment which is cost-sensitive and stable in working condition.

[0010] Optionally, the determination step until the preset reverse bias voltage establishment condition is met comprises: S21, the amplitude of the reverse bias voltage at the control end of the power switch tube is acquired; and S22, the amplitude of the reverse bias voltage is compared with a preset target reverse bias voltage threshold value, and if the amplitude of the reverse bias voltage is greater than or equal to the target reverse bias voltage threshold value, it is determined that the reverse bias voltage establishment condition is met.

[0011] By adopting the technical scheme, adaptive determination is realized based on voltage feedback, without relying on fixed timing, and different element parameter tolerances, temperature changes and input voltage fluctuation scenarios can be accurately matched. Only when the reverse bias voltage reaches the target reverse bias voltage threshold can the working signal be switched, ensuring that the reverse bias voltage clamping is reliable and effective, preventing determination errors caused by parameter drift, and further improving system adaptability and stability.

[0012] Optionally, the driving circuit further comprises a driving level switching circuit connected to the primary side of the driving transformer, and a control end of the driving level switching circuit is connected to the control circuit; in step S1, the specific method of controlling the driving transformer to output the pre-charging driving voltage comprises: the control circuit sends a pre-charging control instruction to the driving level switching circuit, controls the driving level switching circuit to input a first voltage to the driving transformer, and controls the driving transformer to output the pre-charging driving voltage; in step S3, the specific method of controlling the driving transformer to switch to output the working driving voltage comprises: when the preset reverse bias voltage establishment condition is met, the control circuit sends a working control instruction to the driving level switching circuit, controls the driving level switching circuit to input a second voltage to the driving transformer, and controls the driving transformer to switch to output the working driving voltage.

[0013] By adopting the technical scheme, the input voltage of the driving transformer is accurately adjusted by relying on the cooperation of the control circuit and the driving level switching circuit, and then the switching of the output voltage amplitude is realized. The logic link is clear and controllable, and the smooth transition of the pre-charging and working states can be ensured, thereby reducing the impact of voltage mutation on the circuit.

[0014] Optionally, the reverse bias voltage generation circuit comprises an auxiliary switch tube, a rectifier diode, an energy storage capacitor and a voltage stabilizing diode; the rectifier diode is arranged between the control end and the output end of the auxiliary switch tube, and constitutes a switching type charging circuit; the input end of the switching type charging circuit is connected to the secondary side of the driving transformer, the output end of the switching type charging circuit is connected to the first end of the energy storage capacitor, the second end of the energy storage capacitor is connected to the gate of the power switch tube, and the voltage stabilizing diode is connected to the energy storage capacitor in parallel, and is used to clamp the voltage across the energy storage capacitor, so as to form the reverse bias voltage; in step S1, the pre-charging driving voltage charges the energy storage capacitor through the switching type charging circuit, so that a potential difference is established across the energy storage capacitor, and the reverse bias voltage acting on the gate of the power switch tube is formed, and the amplitude of the reverse bias voltage is configured to be lower than the turn-on threshold voltage of the power switch tube.

[0015] By adopting the technical scheme, the switching type charging circuit can efficiently charge the energy storage capacitor, and the voltage stabilizing diode clamps the reverse bias voltage, so as to ensure that the voltage is stable in a safe range. The pre-charging driving voltage realizes reliable establishment of the reverse bias voltage through the circuit, and the structure is mature and low in cost. In cooperation with the active control logic, the performance is ensured while the hardware cost is controlled.

[0016] Optionally, the preset first time length threshold is 0.3 ms to 0.5 ms, and the preset first cycle number threshold is 40 to 60 switching cycles.

[0017] By adopting the above technical solution, the first time length threshold of 0.3 ms to 0.5 ms or the threshold of 40 to 60 switching cycles can be compatible with energy storage capacitors of different capacitance values, ensure that they are fully charged and establish stable reverse bias voltage, and improve the adaptability of the system to different device parameters.

[0018] Optionally, the method further comprises a monitoring and protection step: starting a timer or a counter while outputting the pre-charge driving voltage, and counting the duration of the pre-charge driving voltage or the number of switching cycles; if the duration reaches a preset second time length threshold, or the cycle number reaches a preset second cycle number threshold, and the amplitude of the reverse bias voltage at the control end of the power switch tube is still less than the target reverse bias voltage threshold, it is determined that the driving circuit has a fault, the second time length threshold is greater than the first time length threshold, and the second cycle number threshold is greater than the first cycle number threshold; stop outputting the pre-charge driving voltage, and lock the system or output a fault alarm signal.

[0019] By adopting the above technical solution, the fault diagnosis and protection mechanism is added to prevent the problem that the traditional hardware circuit continues to work abnormally until it is damaged when the reverse bias voltage fails to be established. When it is detected that the reverse bias voltage cannot meet the standard within the maximum allowed time, the driving is stopped in time and the protection is triggered, which can prevent the power switch tube from being damaged due to the lack of reverse bias voltage clamping, and can also prompt maintenance through the fault alarm, thereby improving the safety and maintainability of the system.

[0020] In a second aspect, the application provides a driving system for a power switch tube, which adopts the following technical solution:

[0021] The driving system for the power switch tube comprises a control circuit and a driving circuit, the control circuit is configured to generate control instructions and driving control signals, and the input end of the driving circuit is connected to the control circuit and the output end is used to connect the power switch tube; wherein the driving circuit comprises a driving level switching circuit, a driving transformer and a reverse bias voltage generation circuit, the input end of the driving level switching circuit is connected to the control circuit and is configured to adjust the amplitude of the output voltage according to the control instructions; the primary side of the driving transformer is connected to the output end of the driving level switching circuit, and is used to isolate and transmit the voltage signal output by the driving level switching circuit to the secondary side; the reverse bias voltage generation circuit is connected between the secondary side of the driving transformer and the control end of the power switch tube; the control circuit controls the driving level switching circuit to output voltage signals of different amplitudes, which are transmitted through the driving transformer, and cooperate with the reverse bias voltage generation circuit to establish a reverse bias voltage or a driving conduction voltage at the control end of the power switch tube.

[0022] By adopting the technical solutions, an intelligent driving link of "detection-decision-execution" is constructed, the driving level switching circuit realizes flexible adjustment of voltage amplitude, the driving transformer guarantees electrical isolation and signal transmission, and the reverse bias voltage generation circuit completes establishment of the reverse bias voltage. The modules work cooperatively to realize active reverse bias voltage driving control, improve the reliability defects of the traditional passive scheme, and meanwhile, the mature circuit topology is utilized to balance performance, cost and realizability.

[0023] Optionally, the driving level switching circuit comprises at least one of a digital potentiometer, a programmable power supply or a multi-path power supply switching switch, and is used to switch between the first voltage and the second voltage after receiving an instruction of the control circuit.

[0024] By adopting the technical solutions, multiple selection schemes of the driving level switching circuit are provided, the digital potentiometer, the programmable power supply and the multi-path power supply switching switch are all mature power electronic devices or modules, and have strong compatibility and high control precision. Different selection schemes can adapt to application requirements of different costs and different control precisions, and enhance flexibility and scalability of the system.

[0025] Optionally, the system further comprises a driving level detection circuit connected between the gate of the power switch tube and the control circuit, and used to collect the gate driving voltage and feed back to the control circuit.

[0026] By adopting the technical solutions, the driving level detection circuit provides a voltage feedback signal for the control circuit, so that the control circuit can monitor the establishment of the reverse bias voltage in real time, and realize adaptive determination and fault diagnosis functions. The introduction of the feedback mechanism enables the system to have intelligent adjustment capability, can cope with complex working conditions such as component parameter drift and temperature change, and further improves the reliability of the reverse bias voltage clamping and the overall safety of the system.

[0027] In summary, the present application includes at least one of the following beneficial technical effects:

[0028] 1. A pre-charge driving voltage lower than a conduction threshold of the power switch tube is output first, the reverse bias voltage generation circuit is driven to establish the reverse bias voltage under the premise that the power switch tube is not conducting, and then the normal working driving voltage is switched to after the establishment condition is met, so as to realize the active control logic of "first building negative voltage and then conducting switch". Compared with the traditional passive negative voltage generation scheme, the problem of negative voltage establishment lag in the starting, frequency conversion or dynamic load scene is improved, the gate of the power switch tube is ensured to be in a safe negative voltage state from the first normal driving period, and the upper and lower bridge arms are prevented from being short-circuited.

[0029] 2. Timing determination and voltage feedback adaptive determination are supported, different working condition requirements are adapted to, and a fault diagnosis and protection mechanism is additionally provided, so that the reverse bias voltage establishment failure fault can be detected in time and protection is triggered, circuit damage is prevented, and system safety and maintainability are improved.

[0030] 3. The system relies on existing MCU and other control resources, realizes hardware security through software algorithm upgrade, does not need complex and expensive new components, balances cost effectiveness and performance advantages, and the circuit topology is mature and flexible in selection, suitable for isolation transformer driving scenes of various double-ended conversion topologies such as full-bridge and half-bridge. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a driving system structure diagram provided by the related art;

[0032] Figure 2 is another driving system structure diagram provided by the related art;

[0033] Figure 3 is a driving signal timing simulation waveform diagram provided by the related art;

[0034] Figure 4 is a driving system structure diagram provided by the embodiments of the present application;

[0035] Figure 5 is another driving system structure diagram provided by the embodiments of the present application;

[0036] Figure 6 is a step flowchart of a driving method provided by the embodiments of the present application;

[0037] Figure 7 is a driving signal timing simulation waveform diagram provided by the embodiments of the present application;

[0038] Figure 8 is a logic flowchart of a driving method provided by the embodiments of the present application;

[0039] Figure 9 is another logic flowchart of a driving method provided by the embodiments of the present application.

[0040] Explanation of reference signs:

[0041] 1, control circuit; 2, driving circuit; 3, power switch tube; 4, driving level detection circuit. DETAILED DESCRIPTION

[0042] The following will be described in detail in combination with the accompanying Figures 1-9 The present application is further described in detail.

[0043] Reference is made to Figure 1The transformer-isolated drive structure provided for related technologies uses a MUC to output complementary A and B PWM drive waveforms, which, after isolation by the isolation transformer T1, drive the upper bridge arm MOSFET switch Q1 and the lower bridge arm MOSFET switch Q2. When the drive level is positive, Q1 is turned on via D1. When the drive level changes to 0 or negative, the P-channel MOSFET auxiliary switch Q1A pulls the drive level of Q1 down to 0, turning off Q1. The turn-on and turn-off of Q2 are similar and will not be described further.

[0044] When Q1 is on, Q2 should be off. However, in practical applications, when Q1 is on, the drain voltage of Q2 rises rapidly. Due to the presence of the MOSFET parasitic capacitor Cgd (not shown in the figure), a voltage spike will couple at the gate Vg2 of Q2, which may cause Q2 to be falsely turned on, resulting in shoot-through damage to the upper and lower bridge arms. The false turn-on situation of Q1 is similar.

[0045] To reduce the risk of shoot-through short circuits in the upper and lower bridge arm MOSFETs, it is typically necessary to pull their gate drive voltage to a specific negative voltage (for N-type MOSFETs) during MOSFET turn-off. For example, when the lower bridge arm Q2 is turned off, its gate voltage Vg2 is clamped to a specific negative value. When the upper bridge arm Q1 is turned on, even if interference voltage is coupled to the gate of Q2, it ensures that Vg2 remains below the turn-on threshold, thereby reducing the shoot-through risk of both the upper and lower bridge arms. Figure 2 As shown, a negative voltage generation circuit is set at the input terminals of the upper and lower bridge arm MOSFETs. Its principle lies in utilizing the charge pump characteristic. Taking Q2 as an example, when the isolation transformer T1 is driven positively, Q2 is driven through D2, simultaneously charging capacitor C2. The capacitor is positive on the left and negative on the right, with the maximum voltage across the capacitor being the regulated voltage Vz2 of the Zener diode Z2. When the drive turns negative, the PMOS turns on, and Vg2 discharges. The left end of the capacitor voltage is pulled low to 0 by the PMOS. Since the capacitor voltage cannot change abruptly, the right end of the capacitor voltage is clamped at -Vz2, meaning the gate of Q2 is pulled low at -Vz2. As long as the capacitor energy remains constant, the gate of Q2 will always be clamped at -Vz2.

[0046] like Figure 3 The figure shows the simulated drive waveforms for a transformer isolation drive scheme with negative voltage compensation. The upper waveform Vab in the figure represents the waveform of the primary winding of the drive transformer, and the lower waveform represents the drive waveform generated at Vg2 after passing through the isolation transformer. Due to the presence of C2, the negative capacitor of Vg2 gradually builds up (approximately 10 cycles), and the final negative voltage reaches -Vz2.

[0047] In the related art, the mainstream negative pressure generation scheme adopts a passive topology structure of "diode D, voltage stabilizing tube Z and capacitor C". The reliability of the negative pressure establishment of this topology completely depends on the matching relationship between the RC time constant and the switching frequency, and is a passive response, slow adjustment and uncontrollable working process. Under the working conditions of system startup, parameter drift, variable frequency operation or dynamic load switching, the negative pressure clamping failure is easily caused by the untimely and unreliable establishment of the clamping capacitor voltage, and then the risk of the upper and lower bridge arms of the bridge circuit is straight through.

[0048] In view of the above defects, although some improvement schemes are proposed in the prior art, or a complex auxiliary control circuit 1 is introduced, resulting in a substantial increase in the hardware cost of the system; or customized special devices are used, which reduces the universality and compatibility of the scheme.

[0049] Therefore, with reference to Figure 4 The driving system of the power switch tube disclosed in the embodiments of the present application comprises a control circuit 1 and a driving circuit 2. The control circuit 1 is configured to generate control instructions and driving control signals. The input end of the driving circuit 2 is connected to the control circuit 1, and the output end is used to connect the power switch tube 3. The driving circuit 2 comprises a driving level switching circuit, a driving transformer T1 and a reverse bias voltage generation circuit. The input end of the driving level switching circuit is connected to the control circuit 1, and is configured to adjust the amplitude of the output voltage according to the control instructions. The primary side of the driving transformer is connected to the output end of the driving level switching circuit, and is used to isolate and transmit the voltage signal output by the driving level switching circuit to the secondary side. The reverse bias voltage generation circuit is connected between the secondary side of the driving transformer and the control end of the power switch tube 3. The control circuit 1 controls the driving level switching circuit to output voltage with different amplitudes, which is transmitted through the driving transformer, and cooperates with the reverse bias voltage generation circuit to establish a reverse bias voltage or a driving conduction voltage at the control end of the power switch tube 3.

[0050] Specifically, the driving system of the present application is suitable for driving power switch devices of full-bridge, half-bridge and other power electronic topologies, such as Figure 4As shown, the upper and lower bridge arm power switches 3 (upper bridge power switch Q1, lower bridge power switch Q2) of the half-bridge topology are shown. In the drive system, the control circuit 1 can be a micro control unit (MCU), a digital signal processor (DSP) or a field programmable gate array (FPGA), which can generate pre-charge, working drive and other control instructions, and output PWM signals (such as DrvA, DrvB in the figure); the drive circuit 2 includes a drive level switching circuit, a drive transformer T1 and a reverse bias voltage generating circuit, wherein the drive level switching circuit can be a level conversion chip, a programmable power supply or a multi-path power supply switching network, a digital potentiometer controlled amplification ratio switching circuit, etc., which can switch output voltage signals of different amplitudes according to the instructions output by the control circuit 1, to meet the different voltage requirements of pre-charge drive and working drive, and can switch output voltage of different amplitudes according to the control instructions, the drive transformer T1 is an isolated pulse transformer, which realizes electrical isolation between the control side and the power side, and the reverse bias voltage generating circuit is composed of auxiliary switches (Q1A, Q1B), rectifier diodes (D1, D2), energy storage capacitors (C1, C2) and voltage stabilizing diodes (Z1, Z2), which is used to generate a reverse bias voltage. The drive system of the power switch 3 of the present application can ensure that the MOSFET gate is in a safe state from the first normal drive switching cycle by active control, reducing the risk of false start-up.

[0051] The following will take the driving process of the lower bridge power switch Q2 as an example for description:

[0052] Referring to Figure 4 , after the system is powered on, the control circuit 1 outputs a pre-charge drive signal (PWM pulse, Vg_pre), and the drive level switching circuit outputs a first voltage of low amplitude. The low amplitude voltage is transmitted to the secondary side through the primary side isolation of the drive transformer T1 to form a pre-charge drive voltage.

[0053] In the T1 secondary side, the inductive current charges the energy storage capacitor C2 through the rectifier diode D2; at the same time, the voltage stabilizing diode Z2 connected in parallel across C2 clamps the voltage across C2. Through this charging process, a stable DC voltage difference (for example, 2V) is established across the energy storage capacitor C2, which constitutes a reverse bias voltage source for the power switch 3 (Q2). During this pre-charge phase, since the pre-charge drive voltage amplitude is low (for example, 5V voltage is output through DrvA_1), after deducting the voltage drop on C2, the effective voltage (5-2=3V) applied to the control end (Vg2) of Q2 is lower than the conduction threshold (for example, 4V) of Q2, so Q2 remains off.

[0054] Subsequently, the control circuit 1 outputs the working drive signal (Vg_nom), and the drive level switching circuit outputs the second voltage switched to a high amplitude value (for example, outputs a 18V voltage through DrvA_1). The high amplitude value voltage is transmitted to the secondary side through T1 to form a working drive voltage, which is superimposed on the voltage established by the energy storage capacitor C2. At this time, after the voltage amplitude output by T1 overcomes the reverse voltage drop of C2, the remaining voltage (for example, 18V-2V=16V) is greater than the conduction threshold (for example, 4V) of Q2, so that Q2 can be reliably turned on. During the low period of the PWM signal, since T1 outputs zero or low, the voltage across C2 will cause the control end of Q2 to present a negative voltage (for example, -2V), thereby achieving reliable turn-off. The driving process of the upper bridge Q1 is symmetrical to Q2, and the pre-charging and working drive are independently completed through the other group of secondary sides of T1, thereby realizing isolated control of the upper and lower bridge arms.

[0055] It can be understood that in the embodiment, the drive system realizes flexible adjustment of the voltage amplitude value through the drive level switching circuit, the drive transformer guarantees electrical isolation and signal transmission, and the reverse bias voltage generation circuit completes the establishment of the reverse bias voltage. The modules work cooperatively to realize active reverse bias voltage drive control, improve the reliability defects of the traditional passive scheme, and at the same time, take into account the performance, cost and realizability by using mature circuit topology.

[0056] It should be noted that considering that the time constant required for the energy storage capacitor C1 / C2 to charge to the target reverse bias voltage is relatively fixed under certain hardware circuit parameters (such as drive transformer ratio, energy storage capacitor capacity, loop impedance, etc.). Therefore, the control circuit 1 (such as MCU) can internally preset a fixed "pre-charging time" (the time can be obtained by theoretical calculation or experimental calibration, and a certain safety margin is reserved, for example, set to tens of microseconds to several milliseconds). After the system is powered on, the control circuit 1 first outputs the pre-charging control instruction for the preset time, and after the timing ends, the control circuit 1 defaults that the reverse bias voltage has been established, and then automatically switches to the normal working drive mode.

[0057] In this open-loop control implementation, the drive level detection circuit 4 and its feedback loop on the hardware can be omitted, which can further reduce the hardware cost and wiring complexity of the circuit, reduce the system size, and be suitable for cost-sensitive or space-limited application scenarios.

[0058] For example, the control circuit 1 can be a microcontroller unit (MCU), and the drive level switching circuit can be a transistor (for example, a MOSFET or a BJT). Figure 5As shown, in an embodiment, the driving system of the power switch tube 3 is provided with a driving level detection circuit 4, which collects the voltage at the control end of the power switch tube 3 through a sampling circuit (not shown in the figure) composed of a voltage dividing resistor and an operational amplifier, and feeds back to the control circuit 1, and the driving level detection circuit 4 provides a voltage feedback signal for the control circuit 1, so that the control circuit 1 can monitor the establishment of the reverse bias voltage in real time, and realize the functions of adaptive judgment and fault diagnosis. Specifically, the driving level detection circuit 4 collects the voltage signal of Vg2 and feeds back to the control circuit 1. When it is determined that the amplitude of the reverse bias voltage (i.e. the voltage across C2) meets the standard, the control circuit 1 determines that the pre-charging is completed, and then outputs the working driving signal (Vg_nom).

[0059] It can be understood that the driving system of the present application constructs an intelligent driving link of "detection-decision-execution", and the introduction of the feedback mechanism enables the system to have intelligent adjustment capability, which can cope with complex working conditions such as component parameter drift and temperature change, and further improves the reliability of the reverse bias voltage clamping and the overall safety of the system.

[0060] It should be noted that in the present embodiment, the power switch tube 3 (Q1, Q2) is an N-type MOSFET, and the corresponding reverse bias voltage is negative voltage, so as to ensure that the voltage of the gate with respect to the source is lower than the turn-on threshold, so that the power switch tube 3 can be reliably turned off; in other embodiments, when the power switch tube 3 is a P-type MOSFET, the corresponding reverse bias voltage is positive voltage, and the polarity of the reverse bias voltage is opposite to the polarity required for the power switch tube 3 to be turned on, which functions to make the effective voltage at the control end of the power switch tube 3 lower than the turn-on threshold, so as to realize reliable turn-off of the device and inhibit unintended conduction.

[0061] It should be noted that in the design of the conventional driving circuit 2, the design habit generally followed by technicians is to pursue "fast response of the driving signal" and "as strong driving capability as possible", that is, it is generally believed that the device should respond immediately and enter the conduction state as soon as the driving signal is sent out. However, the present embodiment optimizes the relationship between system safety and performance by introducing the pre-charging timing (signal but not conduction), and suppresses the problem of mis-conduction of high-voltage and high-power devices at the starting moment by driving in stages with variable amplitude. Specifically, the present application uses the low-amplitude pre-charging stage to ensure that the gate of the power device has established a negative voltage clamping environment before it is subjected to the impact of high-voltage bus voltage. This active defense mechanism reduces the risk of mis-conduction caused by the Miller effect or line noise from the physical layer, thereby improving the robustness and reliability of the system.

[0062] In an embodiment, the drive level switching circuit includes at least one of a digital potentiometer, a programmable power supply, or a multi-path power supply switching switch, for switching between the first voltage amplitude and the second voltage amplitude upon receiving the instruction of the control circuit 1. Among them, the digital potentiometer can be adapted to small power and high precision driving scenarios, such as laboratory level power switch tube 3 test platform or small power electronic equipment, which has the advantages of small size and fine adjustment step, and can realize millivolt level voltage amplitude fine tuning through the serial instruction of the control circuit 1, meet the matching requirements of pre-charge drive voltage and working drive voltage; the programmable power supply is suitable for medium and large power, multi-working condition switching industrial scenarios, such as the drive system of electric arc furnace, frequency converter and other equipment, which supports wide voltage output range and fast amplitude switching response, can flexibly configure multiple voltage parameters according to the conduction threshold and reverse bias voltage requirements of different power switch tubes 3, and has overvoltage and overcurrent protection functions to improve the stability of the drive system; the multi-path power supply switching switch is more suitable for cost-sensitive and fixed topology standardized driving scenarios, such as mass-produced general-purpose power modules, which realize fast switching by pre-setting two fixed amplitude power supplies and cooperating with the level signal of the control circuit 1, have the characteristics of simple structure, high reliability and low maintenance cost, and can meet the cost-effective demand of large-scale application.

[0063] Specifically, when the multi-path power supply switching switch scheme is adopted, the drive circuit 2 can preset two independent DC power supplies VCC_pre (for example, 5V) and VCC_work (for example, 18V). The control circuit 1 controls an analog switch (such as a high-speed MOSFET switch group) through a simple GPIO high-low level signal to select VCC_pre or VCC_work to access the primary side power supply loop of the drive transformer T1, realizing fast switching of two voltage grades. This scheme has low cost and fast response. When the programmable power supply or digital potentiometer controlled operational amplifier scheme is adopted, the control circuit 1 can send digital instructions to the circuit through SPI or I2C serial bus to accurately set the amplitude of the output voltage. This scheme has high flexibility, not only can realize two-grade switching, but also can realize smooth transition or multi-stage regulation of voltage, and is suitable for high-performance application scenarios that require fine management of drive waveforms.

[0064] It can be understood that the selection scheme of providing multiple drive level switching circuits provides digital potentiometers, programmable power supplies, and multi-path power supply switching switches, which are mature power electronic devices or modules, have strong compatibility and high control precision. Different selection types can adapt to different cost and different control precision application requirements, enhancing the flexibility and scalability of the system.

[0065] As shown in Figure 6 The application also discloses a power switch tube driving method, applied to the drive circuit 2, the method comprising the steps of:

[0066] S1, control the driving transformer to output a pre-charge driving voltage, the amplitude of the pre-charge driving voltage is configured to be able to drive the reverse bias voltage generation circuit to work to establish the reverse bias voltage, and make the effective driving voltage applied to the control end of the power switch tube 3 remain below the turn-on threshold voltage of the power switch tube 3;

[0067] Specifically, in combination with the half-bridge topology driving system shown in Figure 4 or Figure 5 The following bridge power switch tube Q2 driving process is taken as an example, and the specific execution process of this step is as follows: the control circuit 1 outputs a pre-charge control instruction (a pre-charge driving signal), and the driving level switching circuit outputs a first voltage in response to the instruction. The first voltage is input to the primary side of the driving transformer T1, and after realizing electrical isolation between the control side and the power side through the driving transformer T1, the signal is transmitted to the secondary side, and a pre-charge driving voltage is generated in the secondary side by induction. The pre-charge driving voltage has a first voltage amplitude, for example, 5V. In the secondary side loop of the driving transformer T1, the induction current flows from the rectifier diode D2 in the reverse bias voltage generation circuit to the energy storage capacitor C2, completing the charging of the energy storage capacitor C2. At the same time, the zener diode Z2 connected in parallel across the energy storage capacitor C2 works synchronously to clamp the voltage across the energy storage capacitor C2, ensuring the stability of the charging process. Through the above charging process, a stable DC voltage difference (for example, 2V) is gradually established on the energy storage capacitor C2, which constitutes a reverse bias voltage source for the power switch tube Q2.

[0068] It should be noted that the first voltage amplitude (for example, 5V) set in this step can drive the reverse bias voltage generation circuit to work (for example, greater than the conduction voltage drop of the rectifier diode D2, the Schottky diode 0.2-0.2V, and the silicon-based rectifier diode 0.7V), and after deducting the 2V voltage drop on the energy storage capacitor C2, the effective voltage finally applied to the control end of Q2 (Vg2) is still lower than the turn-on threshold of Q2 (for example, 4V). Therefore, during the entire pre-charge phase, the power switch tube Q2 always remains in the off state, avoiding the risk of false turn-on during the pre-charge phase.

[0069] S2, maintain the output of the pre-charge driving voltage until the preset reverse bias voltage establishment condition is met;

[0070] In an embodiment, the reverse bias voltage establishment condition can be set by a fixed determination method of timing. Specifically, as shown in Figure 4 the control circuit 1 starts the built-in timer or counter synchronously while outputting the driving signal, and counts the duration of the pre-charge driving voltage or the number of switching cycles. If the counted duration reaches a preset first time threshold, or the counted cycle number reaches a preset first cycle number threshold, it is determined that the reverse bias voltage establishment condition is met.

[0071] It can be understood that the timing determination logic is simple and direct, does not require additional voltage acquisition circuit, and can be realized by relying on the timer or counter built in the control circuit 1, thereby reducing the system hardware complexity and production cost. The preset time length or cycle threshold is verified by experiments, and under the conventional element parameters and standard working conditions, can ensure that the reverse bias voltage generation circuit fully completes the charging, meets the reliability requirements of most general power electronic devices, and is especially suitable for cost-sensitive and stable working condition of large-scale application environment.

[0072] In an embodiment, the reverse bias voltage establishment condition can also be set by an adaptive determination method of voltage feedback, as shown in FIG. 4, and the determination steps include: Figure 5

[0073] S21, the drive level detection circuit 4 acquires the reverse bias voltage amplitude (i.e. the absolute value of the energy storage capacitor C2 voltage value) on the energy storage capacitor C2 of the power switch tube Q2 control end (Vg2) in real time;

[0074] S22, the control circuit 1 compares the acquired reverse bias voltage amplitude with the preset target reverse bias voltage threshold (for example, 2V). If the acquired reverse bias voltage amplitude is greater than or equal to the target reverse bias voltage threshold, it is determined that the reverse bias voltage establishment condition is met.

[0075] Specifically, the voltage input at the Q2 control end is acquired in real time by the drive level detection circuit 4. Since in the pre-charging process, the off gap of the PWM pulse period, the voltage value is negative (for example, -2V), and the circuit converts it into a positive voltage amplitude signal or a digital signal feedback to the MCU (control circuit 1). The preset target reverse bias voltage threshold is set to 2V (corresponding to a physical -2V reverse bias depth). If the feedback reverse bias voltage amplitude gradually rises and reaches 2V and above (for example, 2.2V is acquired, which means that the negative voltage depth reaches -2.2V), the control circuit 1 determines that the reverse bias voltage has been reliably established (i.e. the energy storage capacitor C2 has sufficient energy), at which point the pre-charging drive voltage can be stopped and the working drive phase can be switched to.

[0076] By adopting the above technical scheme, adaptive determination is realized based on voltage feedback, without relying on fixed timing, which can accurately match different element parameter tolerances, temperature changes and input voltage fluctuation scenarios. For example, when the ambient temperature rises slightly, the voltage feedback mechanism can sense the charging progress in real time, and prolong the pre-charging maintenance time until the voltage meets the standard; and if the input voltage fluctuates, the voltage acquisition can also ensure that the reverse bias voltage always reaches the target reverse bias voltage threshold. Only when the reverse bias voltage reaches the target reverse bias voltage threshold can the working signal be switched, ensuring that the reverse bias voltage clamping is reliable and effective, preventing determination errors caused by parameter drift, and further improving the adaptability and stability of the system. ​

[0077] It should be noted that the preset "target reverse bias voltage threshold" is determined based on the safety cutoff requirement of the power switch tube 3. Since in the precharge stage, the precharge drive voltage (for example, 5V) output by the drive transformer is higher than the turn-on threshold voltage (for example, 4V) of the N-type power switch tube Q2, if a sufficient voltage difference has not been established across the energy storage capacitor C2, directly applying the drive voltage signal can cause Q2 to conduct unexpectedly.

[0078] Therefore, the definition of the target reverse bias voltage threshold (Vta) needs to meet the following condition: the difference between the precharge drive voltage (VD) and the target reverse bias voltage threshold (Vta) is less than the turn-on threshold voltage Vth of the power switch tube 3 (i.e., VD-Vta < Vth).

[0079] In this embodiment, if the precharge drive voltage is 5V and the Q2 turn-on threshold is 4V, considering the circuit noise tolerance and safety margin, the target reverse bias voltage threshold is set to 2V. At this time, the zener diode Z2 connected in parallel across the capacitor C2 is preferably a 2V specification that adapts to this threshold, for clamping after the voltage is established.

[0080] S3, control the drive transformer to switch output a working drive voltage, the working drive voltage is configured to be higher than the sum of the turn-on threshold voltage and the reverse bias voltage of the power switch tube 3, to drive the power switch tube 3 to turn on.

[0081] Specifically, the control of the drive transformer to switch output a working drive voltage specifically includes: when the preset reverse bias voltage establishment condition is met, the control circuit 1 sends a working control instruction (working drive signal) to the drive level switching circuit, controls the drive level switching circuit to input a second voltage higher than the first voltage to the drive transformer, so that the drive transformer switches output the working drive voltage (for example, 18V).

[0082] It should be noted that the amplitude of the working drive voltage is higher than the sum of the turn-on threshold voltage and the reverse bias voltage of the power switch tube 3, for example, the preset turn-on threshold voltage of Q2 is 4V, and the reverse bias voltage established through the precharge stage is 2V, the sum of which is 6V, and the working drive voltage amplitude set in this embodiment is 18V, which is much higher than 7V; When the second voltage is transmitted to the secondary side through the drive transformer T1 to form the working drive voltage, it is superimposed on the 2V reverse bias voltage already established across the energy storage capacitor C2, after offsetting the reverse voltage drop of the reverse bias voltage, the effective drive voltage applied to the Q2 control end (Vg2) is 16V, which is still higher than the 4V turn-on threshold of Q2, so that Q2 can be reliably driven to turn on.

[0083] In this embodiment, by cooperating the control circuit 1 with the drive level switching circuit, the input voltage of the drive transformer is accurately adjusted, and then the switching of the output voltage amplitude is realized. The logic link is clear and controllable, which can ensure the smooth transition of pre-charging and working state, and prevent the impact of voltage mutation on the circuit.

[0084] It can be understood that the driving method of the present application first outputs a pre-charging driving voltage lower than the conduction threshold of the power switch tube 3, drives the reverse bias voltage generation circuit to establish a reverse bias voltage under the premise that the power switch tube 3 is not conducting, and then switches to a normal working driving voltage after the establishment condition is met, to realize the active control logic of "first establishing reverse bias voltage and then turning on the switch". Compared with the traditional passive negative voltage generation scheme, the problem of negative voltage establishment lag in the starting, frequency conversion or dynamic load scene is improved, and the gate of the power switch tube 3 is ensured to be in a safe reverse bias voltage state from the first normal driving period, preventing the short circuit of the upper and lower bridge arms.

[0085] As shown in Figure 7 To describe the switching logic of the driving signal and the establishment process of the reverse bias voltage, the time sequence simulation waveform diagram of the driving signal in the present application is shown. In an embodiment, the preset first time threshold is 0.3ms to 0.5ms, and the preset first cycle number threshold is 40 to 60 switching cycles. Preferably, the preset first time threshold is 0.4ms, and the first cycle number threshold is 40 PWM cycles (the pre-charging driving signal is in the form of PWM). The control circuit 1 outputs the pre-charging driving signal (Vab) while starting the timer. When the duration displayed by the timer reaches 0.4ms or the number of output PWM cycles counted by the counter reaches 40, it is determined that the pre-charging is completed, and the reverse bias voltage establishment condition is met. The 0~0.0004s (0.4ms) stage in the figure corresponds to the pre-charging driving stage with low amplitude, and the waveform is switched to a high amplitude pulse after 0.0004s, that is, the normal driving stage is entered after the pre-charging is completed.

[0086] The waveform Vab is a PWM signal output by the control circuit 1 (MCU). After being coupled by the drive level switching circuit and the isolation transformer, it is applied to the control end (Vg2) of the power switch tube 3. In 0s~0.0004s (pre-charging stage): the MCU controls the primary side of the isolation transformer to generate a low voltage excitation, so that the output Vab presents a relatively low amplitude AC pulse waveform (for example, ±5V), and the drive level switching circuit inputs a first voltage to the drive transformer. The signal in this stage is mainly used to provide energy to the energy storage capacitor C2. After 0.0004s (normal driving stage): the MCU switches the control strategy, so that the amplitude of the output Vab is expanded to a larger amplitude AC pulse waveform (for example, ±18V).

[0087] Vg waveform is the gate-source voltage of power switch tube 3, which represents the voltage difference across energy storage capacitor C2. 0s~0.0004s: although the input signal Vab maintains a constant amplitude, the Vg waveform presents a trend of overall downward shift. This is because the energy storage capacitor C2 is accumulating charge, and the voltage across it (i.e. the reverse bias voltage) gradually rises. According to the series voltage relationship, the DC level of Vg2 is pulled down, and the positive peak of Vg2 is shifted downward and always below the turn-on threshold of MOSFET (Vth, for example, 4V), ensuring that the MOSFET is reliably turned off (not conducting) during pre-charging. At the same time, the negative peak of Vg2 gradually drops to a preset clamping voltage (for example, -2V), indicating that the negative voltage establishment is complete.

[0088] After 0.0004s, as Vab switches to high amplitude, the positive peak of Vg jumps to a level sufficient to saturate the MOSFET into conduction (for example, 12.5V), while the negative voltage during turn-off is still clamped to a safe value, thus achieving normal driving with negative voltage turn-off protection.

[0089] Referring to Figure 8 In an embodiment, a logic flowchart of the driving method provided by the present application is shown, and the complete process is as follows,

[0090] The system first completes power-on initialization, and then enters the pre-charging driving stage, outputting a low-amplitude pre-charging PWM signal (Vg_pre); at the same time, the driving level Vg2 of power switch tube Q2 is continuously detected to determine whether the reverse bias voltage Vg2_neg reaches the stable voltage of stable voltage tube Vz2 (i.e. the target threshold of reverse bias voltage establishment).

[0091] If Vg2_neg does not reach Vz2, the output of the pre-charging driving signal is continued, and the level detection and threshold judgment are executed in a loop; if Vg2_neg≥Vz2, it indicates that the reverse bias voltage has been stably established, and the switching condition is met, and then the driving circuit 2 is switched to a high-amplitude normal driving signal (Vg_nom), and the system finally enters the normal working state.

[0092] It can be understood that in the present embodiment, the logic of pre-charging to establish a reverse bias voltage, detection threshold meeting, and switching to normal driving is presented, which embodies the reliability of the pre-charging stage and the smoothness of the switching process.

[0093] Referring to Figure 9In an embodiment, the method further comprises a monitoring protection step: starting a timer or a counter while outputting the pre-charge drive voltage, counting the duration of the pre-charge drive voltage or the number of switching cycles; if the duration reaches a preset second duration threshold or the number of cycles reaches a preset second cycle number threshold, and the amplitude of the reverse bias voltage at the control end of the power switch tube 3 is still less than the target reverse bias voltage threshold, it is determined that the drive circuit 2 has a fault; stop outputting the pre-charge drive voltage, and perform a protection action of locking the system or outputting a fault alarm signal.

[0094] In an embodiment, the preset second duration threshold is 1 ms (greater than the first duration threshold 0.4 ms), and the second cycle number threshold is 100 switching cycles (greater than the second cycle number threshold); the control circuit 1 starts the timer and the counter synchronously while outputting the pre-charge drive signal: if the duration counted by the timer reaches 1 ms or the number of switching cycles counted by the counter reaches 100, and the amplitude of the reverse bias voltage at the control end of Q2 fed back by the drive level detection circuit 4 is still lower than the target threshold of 2 V, it is determined that the drive circuit 2 has a fault (for example, the energy storage capacitor C2 is damaged, the rectifier diode D2 is open, etc.); at this time, the drive level detection circuit 4 outputs a fault alarm signal to the control circuit 1 of the system, the control circuit 1 stops outputting the pre-charge drive signal, the drive transformer synchronously stops outputting the pre-charge drive voltage, and the signal output of the drive channel is locked at the same time to prevent the fault from expanding.

[0095] Specifically, the execution process of the monitoring protection step is as follows: after the system is powered on and initialized, the pre-charge PWM drive (Vg_pre) is first output; at the same time, the safety timer is started synchronously to start counting the duration of the pre-charge drive.

[0096] In the pre-charge phase, the drive level Vg2 at the control end of the power switch tube 3 Q2 is continuously detected, and it is judged whether the reverse bias voltage Vg2_neg reaches the stable voltage Vz2 of the stabilizing tube Z2 (i.e. the target reverse bias voltage threshold); if Vg2_neg ≥ Vz2, it indicates that the reverse bias voltage has been stably established, and then the normal working drive signal (Vg_nom) is switched to, and the system enters the normal working state;

[0097] If Vg2_neg does not reach the threshold, the pre-charge drive voltage is continuously output, and it is synchronously detected whether the safety timer is timed out; if the timer is not timed out, it returns to continuously detecting the Vg2 level; if the timer reaches the preset second duration threshold (i.e. timed out), it is determined that the drive circuit 2 has a fault, the PWM output is stopped, and the fault is reported, and finally the shutdown operation is performed to lock the system.

[0098] It can be understood that the additional fault diagnosis and protection mechanism prevents the traditional hardware circuit from continuously abnormal working until damage when the reverse bias voltage fails to establish. When it is detected that the reverse bias voltage fails to meet the standard within the maximum allowed time, the driving is stopped in time and the protection is triggered, which can prevent the power switch tube 3 from being damaged due to the straight-through without the reverse bias voltage clamping, and can also prompt maintenance through fault alarm, thereby significantly improving the system safety and maintainability.

[0099] In an embodiment, the first voltage amplitude ranges from 3V to 6V, and the second voltage amplitude ranges from 10V to 20V; and the preset first cycle threshold is 40 to 60 switching cycles.

[0100] It can be understood that the first voltage amplitude of 3V to 6V can adapt to the conduction threshold (usually 2V-4V) of different types of power switch tubes 3, which can improve the pre-charge stage mis-conduction and drive the reverse bias voltage generation circuit to work stably; the second voltage amplitude of 10V to 20V covers the driving requirements of mainstream power switch tubes 3, and can adapt to the conduction driving of different types of devices such as MOS tubes and IGBTs; and the threshold of 40 to 60 switching cycles can be compatible with energy storage capacitors of different capacitance values, so as to ensure that they are fully charged and a stable reverse bias voltage is established, thereby improving the adaptability of the system to different device parameters.

[0101] It should be noted that in an embodiment, the internal software of the control circuit 1 (such as MCU) can include an initialization module, a PWM generation module, a state switching logic module, and a fault processing module. After the system is powered on, the initialization module configures the PWM timer parameters (frequency, duty cycle) and the GPIO state. Subsequently, the state switching logic module is first placed in the pre-charge state, instructs the PWM generation module to output the driving signal corresponding to the first voltage, and starts an internal timer. The control circuit 1 judges the reverse bias voltage establishment condition through the ADC channel (if there is a driving level detection circuit 4) or only relies on the internal timer. Once the condition is met, the state switching logic module switches to the normal working state, adjusts the PWM driving parameters to output the working driving signal corresponding to the second voltage. If the condition is still not met within the preset timeout threshold, the fault state is entered, the PWM output is closed, and the fault flag bit is set.

[0102] In addition, the present application also provides a data basis for health management and predictive maintenance of the system. In the embodiment employing voltage feedback, the control circuit 1 can record the time required for the reverse bias voltage to be established from zero to the target threshold value each time the system is started. Through long-term trend analysis of this build-up time data, the health status of key components in the reverse bias voltage generation circuit (such as the energy storage capacitor C1 / C2) can be effectively evaluated. If the build-up time is significantly prolonged, it can be an early warning that the components may be aging or failing, guiding preventive maintenance, thereby upgrading the traditional post-failure maintenance to pre-failure warning, enhancing the full life cycle reliability and availability of the power electronic system.

[0103] The above are preferred embodiments of the present application, which do not limit the protection scope of the present application, therefore: any equivalent changes made in the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method of driving a power switching transistor, characterized by, The method is applied to a drive circuit (2) comprising a drive transformer for driving a power switch tube (3) and a reverse bias voltage generation circuit connected between a secondary side of the drive transformer and the power switch tube (3), and comprises the steps of: S1, controlling the drive transformer to output a pre-charge drive voltage, the amplitude of the pre-charge drive voltage being configured to be able to drive the reverse bias voltage generation circuit to establish a reverse bias voltage, and to keep the effective drive voltage applied to the control end of the power switch tube (3) below the turn-on threshold voltage of the power switch tube (3); S2, maintaining the output of the pre-charge drive voltage until a preset reverse bias voltage establishment condition is met; S3, controlling the drive transformer to switch to output a working drive voltage, the working drive voltage being configured to be higher than the sum of the turn-on threshold voltage of the power switch tube (3) and the reverse bias voltage, to drive the power switch tube (3) to turn on.

2. The driving method according to claim 1, wherein The determination step until the preset reverse bias voltage establishment condition is met comprises: starting a timer or a counter to count the duration or the number of switching cycles of the output of the pre-charge drive voltage; if the duration reaches a preset first time threshold or the number of cycles reaches a preset first cycle threshold, it is determined that the reverse bias voltage establishment condition is met.

3. The driving method according to claim 1, wherein The determination step until the preset reverse bias voltage establishment condition is met comprises: S21, acquiring the amplitude of the reverse bias voltage at the control end of the power switch tube (3); S22, comparing the amplitude of the reverse bias voltage with a preset target reverse bias voltage threshold, and if the amplitude of the reverse bias voltage is greater than or equal to the target reverse bias voltage threshold, it is determined that the reverse bias voltage establishment condition is met.

4. The driving method according to claim 1, wherein The drive circuit (2) further comprises a drive level switching circuit connected to the primary side of the drive transformer, and a control circuit (1) connected to the controlled end of the drive level switching circuit; In step S1, the control of the drive transformer to output the pre-charge drive voltage specifically comprises: the control circuit (1) sends a pre-charge control instruction to the drive level switching circuit, controls the drive level switching circuit to input a first voltage to the drive transformer, and makes the drive transformer output the pre-charge drive voltage; In step S3, the control of the drive transformer to switch to output the working drive voltage specifically comprises: after the preset reverse bias voltage establishment condition is met, the control circuit (1) sends a working control instruction to the drive level switching circuit, controls the drive level switching circuit to input a second voltage to the drive transformer, and makes the drive transformer switch to output the working drive voltage.

5. The driving method according to claim 1, wherein The reverse bias voltage generation circuit comprises an auxiliary switch tube, a rectifier diode, an energy storage capacitor and a voltage stabilizing diode. The rectifier diode is arranged between the control end and the output end of the auxiliary switch tube, and constitutes a switching charging circuit. An input end of the switching charging circuit is connected with a secondary side of the drive transformer, and an output end of the switching charging circuit is connected with a first end of the energy storage capacitor. A second end of the energy storage capacitor is connected with a gate of the power switch tube (3). The voltage stabilizing diode is connected in parallel with the energy storage capacitor, and is used for clamping the voltage across the energy storage capacitor, so as to form a reverse bias voltage. In step S1, the pre-charge driving voltage charges the energy storage capacitor through the switching charging circuit, so that a potential difference is established across the energy storage capacitor, and a reverse bias voltage acting on the gate of the power switch tube (3) is formed. The amplitude of the reverse bias voltage is configured to be lower than the turn-on threshold voltage of the power switch tube (3).

6. The driving method according to claim 2, wherein The preset first time length threshold value is 0.3 ms to 0.5 ms, and the preset first cycle number threshold value is 40 to 60 switching cycles.

7. The driving method according to claim 2, wherein The method further comprises a monitoring protection step: While outputting the pre-charge driving voltage, a timer or a counter is started to count the duration of the pre-charge driving voltage or the number of switching cycles. If the duration reaches a preset second time length threshold value, or the number of cycles reaches a preset second cycle number threshold value, and the amplitude of the reverse bias voltage at the control end of the power switch tube (3) is still less than the target reverse bias voltage threshold value, it is determined that the drive circuit (2) has a fault. The second time length threshold value is greater than the first time length threshold value, and the second cycle number threshold value is greater than the first cycle number threshold value. The output of the pre-charge driving voltage is stopped, and the system is locked or an output fault alarm signal is output.

8. A driving system for a power switching transistor, characterized in that, Comprise: a control circuit (1) configured to generate a control instruction; a drive circuit (2) having an input end connected with the control circuit (1) and an output end connected with the power switch tube (3); The drive circuit (2) comprises: a drive level switching circuit having an input end connected with the control circuit (1) and configured to adjust the amplitude of the output voltage according to the control instruction; a drive transformer having a primary side connected with the output end of the drive level switching circuit and a secondary side for transmitting the voltage signal output by the drive level switching circuit; a reverse bias voltage generation circuit connected between the secondary side of the drive transformer and the control end of the power switch tube (3). The control circuit (1) is configured to control the drive level switching circuit to output voltages with different amplitudes, which are transmitted by the drive transformer to establish a reverse bias voltage or a drive turn-on voltage at the control end of the power switch tube (3) in cooperation with the reverse bias voltage generation circuit.

9. The drive system of claim 8, wherein, The drive level switching circuit comprises at least one of a digital potentiometer, a programmable power supply or a multi-path power supply switching switch, and is used for switching between a first voltage and a second voltage after receiving the control instruction of the control circuit (1).

10. The drive system of claim 8, wherein, Further comprising a drive level detection circuit (4) connected between the gate of the power switch tube (3) and the control circuit (1), and used for collecting the gate drive voltage and feeding back to the control circuit (1).

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