A switching device isolated driving circuit

Abstract

The application relates to a kind of switch device isolation driving circuit, a kind of switch device isolation driving circuit includes signal isolation module, multistage amplification and level conversion module and push-pull power amplification module;Signal output end of signal isolation module is connected with the signal input end of multistage amplification and level conversion module;Multistage amplification and level conversion module includes transistor cascade unit, and the signal output end of multistage amplification and level conversion module is connected with the controlled end of push-pull power amplification module;Push-pull power amplification module includes at least one set of complementary drive transistor unit, and a set of complementary drive transistor unit is used to convert control signal into positive and negative drive voltage and output to the gate and source between switch device, to realize the saturation conduction of switch device or reliable shutdown.Make switch device still be able to realize fast, stable conduction and shutdown under high-frequency working condition, to reduce switching loss, improve system efficiency.

Description

Technical Field

[0001] This invention relates to the technical field of switching device drive circuits, and in particular to an isolated drive circuit for switching devices. Background Technology

[0002] Currently, high-power switching devices are widely used in power electronic systems. Their gates typically have large capacitances, requiring the drive circuit to provide sufficient instantaneous peak current for rapid charging and discharging, enabling high-speed turn-on and turn-off. Insufficient drive capability leads to slower switching speeds, increased switching losses, and reduced system efficiency. It can also cause overheating and shorten the device's lifespan. Furthermore, the selection of the drive voltage amplitude directly affects the device's conduction saturation and turn-off reliability. Insufficient drive voltage can easily lead to mis-turn-on or incomplete turn-off, reducing system stability. Therefore, improving the drive current capability and appropriately setting the drive voltage amplitude are crucial for enhancing the performance of high-power switching devices. Summary of the Invention

[0003] To address the problems of insufficient drive current, slow switching speed, high losses, and unreliable turn-off caused by large gate capacitance in high-power switching devices, this application provides an isolated drive circuit for switching devices.

[0004] An isolation drive circuit for switching devices is used in the gate drive control of switching devices. The isolation drive circuit for switching devices includes a signal isolation module, a multi-stage amplification and level conversion module, and a push-pull power amplification module. The signal input terminal of the signal isolation module is used to receive control signals, and the signal output terminal of the signal isolation module is connected to the signal input terminal of the multi-stage amplification and level conversion module. The multi-stage amplification and level conversion module includes a transistor cascade unit, which is used to invert and amplify the control signal output by the signal isolation module and perform level conversion. The signal output terminal of the multi-stage amplification and level conversion module is connected to the controlled terminal of the push-pull power amplifier module. The push-pull power amplifier module includes at least one set of complementary driving transistor units, which are used to convert the control signal into positive and negative driving voltages and output them between the gate and source of the switching device to achieve saturation conduction or reliable turn-off of the switching device.

[0005] By adopting the above technical solution and constructing a drive structure including a signal isolation module, a multi-stage amplification and level conversion module, and a push-pull power amplification module, the transmission integrity and driving capability of the control signal can be effectively improved, enabling the switching devices to achieve fast and stable turn-on and turn-off under high-frequency operating conditions, thereby reducing switching losses, improving system efficiency, and enhancing overall anti-interference performance.

[0006] Preferably, the set of complementary driving transistor units includes an NPN transistor V11, an NPN transistor V12, a PNP transistor V13, and a PNP transistor V14. The base of the NPN transistor V11 is connected to the signal output terminal of the multi-stage amplification and level conversion module. The collector of the NPN transistor V11 is connected to the positive power supply. The emitter of the NPN transistor V11 is connected to the base of the PNP transistor V13. The collector of the PNP transistor V13 is connected to the negative power supply. The emitter of the PNP transistor V13 is connected to the gate terminal of the switching device. The base of the PNP transistor V14 is connected to the signal output terminal of the multi-stage amplification and level conversion module. The collector of the PNP transistor V14 is connected to the negative power supply. The emitter of the PNP transistor V14 is connected to the base of the NPN transistor V12. The collector of the NPN transistor V12 is connected to the positive power supply. The emitters of the NPN transistor V12 and the PNP transistor V13 are connected to the gate terminal of the switching device. A push-pull output node is formed between the emitter of the PNP transistor V12 and the emitter of the NPN transistor V13. This node is used to alternately turn on the PNP transistor V12 and the NPN transistor V13 when the control signal is at different levels, so that the push-pull output node outputs positive and negative driving voltages to drive the gate of the switching device.

[0007] By adopting the above technical solution, a complementary driving structure consisting of two NPN transistors and two PNP transistors is used. This structure can alternately drive the upper and lower bridge arm transistors to conduct when the control signal changes, thereby achieving positive and negative voltage swing control at the output terminal. This provides a higher amplitude and greater current driving capability, meeting the requirements of high-power switching devices for charging and discharging speed and amplitude accuracy.

[0008] Preferably, the push-pull power amplifier module further includes diodes D15 and D16. The anode of diode D15 is connected to the emitter of PNP transistor V14, and the cathode of diode D15 is connected to the push-pull output node. This allows the diode to conduct when the voltage at the push-pull output node is lower than the emitter potential of PNP transistor V14, thus limiting negative overvoltage from damaging the base of NPN transistor V12. The anode of diode D16 is connected to the push-pull output node, and the cathode of diode D16 is connected to the emitter of NPN transistor V11. This allows the diode to conduct when the voltage at the push-pull output node is higher than the emitter potential of NPN transistor V11, thus preventing overshoot of the control signal.

[0009] By adopting the above technical solution, diodes D15 and D16 are introduced as control signal protection elements in the push-pull power amplifier module. This can effectively suppress overshoot and negative voltage spikes generated by abnormal voltage fluctuations at the push-pull output node, and prevent the drive signal from directly impacting the base of the preamplifier tube or the power tube in the subsequent stage, thereby improving the stability and reliability of the circuit during rapid switching.

[0010] Preferably, the push-pull power amplifier module further includes diode D13, diode D14 and filter capacitor C24. Diode D13 and diode D14 are connected in reverse series between the gate and source of the switching device to limit the positive and negative driving voltage between the gate and source, preventing the gate voltage of the switching device from exceeding the corresponding allowable range. The series connection formed by the reverse series connection of diodes D13 and D14 is connected in parallel with the filter capacitor C24 to absorb spike interference in the output signal of the push-pull power amplifier module.

[0011] By adopting the above technical solution, by setting a clamping diode group consisting of D13 and D14 connected in reverse series between the gate and source of the switching device, and a filter capacitor C24 connected in parallel with it, the positive and negative driving voltages can be bidirectionally limited, while absorbing the spike interference in the output waveform, ensuring that the gate voltage is in the safe operating range, and effectively protecting the switching device from overvoltage damage.

[0012] Preferably, the multi-stage amplification and level conversion module includes a transistor cascade unit composed of PNP transistor V3, PNP transistor V5 and NPN transistor V7 cascaded in sequence. The base of PNP transistor V3 is connected to the signal output terminal of the signal isolation module, the collector of PNP transistor V3 is connected to the base of PNP transistor V5, and the emitter of PNP transistor V3 is connected to the positive power supply. The collector of the PNP transistor V5 is connected to the base of the NPN transistor V7, and the emitter of the PNP transistor V5 is connected to the positive power supply; the emitter of the NPN transistor V7 is connected to the negative power supply, and the collector of the NPN transistor V7 serves as the signal output terminal of the multi-stage amplification and level conversion module.

[0013] By adopting the above technical solution, and utilizing a three-stage cascaded structure composed of PNP and NPN transistors, the input control signal can be amplified and its polarity adjusted in multiple stages. This also completes the conversion from low-voltage control logic to positive and negative voltage drive signals, improving the level and drive capability of the drive signal and providing a clear and stable control reference for subsequent push-pull power output.

[0014] Preferably, the multi-stage amplification and level conversion module further includes resistors R38 and R39. The first end of resistor R39 is connected to the positive power supply, the second end of resistor R39 is connected to the first end of resistor R38, the second end of resistor R38 is connected to the collector of the NPN transistor V7, and the common node between the second end of resistor R39 and the first end of resistor R38 serves as the signal output terminal of the multi-stage amplification and level conversion module.

[0015] By adopting the above technical solution, and utilizing a three-stage cascaded structure composed of PNP and NPN transistors, the input control signal can be amplified and its polarity adjusted in multiple stages. This also completes the conversion from low-voltage control logic to positive and negative voltage drive signals, improving the level and drive capability of the drive signal and providing a clear and stable control reference for subsequent push-pull power output.

[0016] Preferably, the isolation drive circuit for the switching device further includes an overcurrent protection module. The overcurrent protection module is used to detect the overcurrent signal in the circuit where the switching device is located. The multi-stage amplification and level conversion module further includes a resistor R32. The first end of the resistor R32 is connected to the collector of the PNP transistor V3, and the second end of the resistor R32 is connected to the base of the PNP transistor V5. The common node between the second end of the resistor R32 and the base of the PNP transistor V5 is connected to the control output terminal of the overcurrent protection module, so as to cut off the drive signal and clamp the output of the push-pull power amplifier module to a negative voltage level when an overcurrent occurs, thereby preventing damage to the switching device.

[0017] By adopting the above technical solution, and introducing a control node between the PNP transistor amplification stage and the overcurrent protection module, the protection signal can accurately intervene in the drive link. When an overcurrent occurs, the front-end control path of the push-pull drive can be cut off in time, and the output terminal can be clamped to a safe level, effectively preventing the burning of switching devices caused by false triggering.

[0018] Preferably, the overcurrent protection module includes a latch control chip D1, a resistor R4, and a capacitor C3. The signal output terminal of the latch control chip D1 is connected to the first terminal of the resistor R4 and the first terminal of the capacitor C3, respectively. The common node between the second terminal of the resistor R32 and the base of the PNP transistor V5 is connected to the second terminal of the resistor R4 and the second terminal of the capacitor C3, respectively.

[0019] By adopting the above technical solution, a latching control chip D1 is introduced into the overcurrent protection module, and used in conjunction with a current-limiting resistor R4 and a filter capacitor C3, so that the protection logic has the ability to maintain its state after being triggered. Even if the fault signal disappears instantaneously, the clamping action can still be maintained, ensuring the integrity of the protection process and the clarity of the action, effectively improving the reliability and controllability of the system's fault response.

[0020] Preferably, the signal isolation module includes an optocoupler N1, which includes a light-emitting diode (LED) portion and a transistor portion. The anode of the LED portion is used to receive control signals, and the cathode of the LED portion is grounded. The first conducting terminal of the transistor portion is connected to the positive power supply, and the second conducting terminal of the transistor portion is connected to the signal input terminal of the multi-stage amplification and level conversion module.

[0021] By adopting the above technical solution and using optocoupler N1 as an isolation element for input signals, electrical isolation between the low-voltage control terminal and the high-voltage drive circuit can be achieved, cutting off the ground loop interference path, preventing interference signals from being fed back to the control side during high-power switching, and improving the anti-interference capability and signal transmission security of the entire drive system.

[0022] Preferably, the signal isolation module further includes resistors R27 and R28. The common node between the first end of resistor R27 and the first end of resistor R28 serves as the signal input terminal of the signal isolation module for receiving control signals. The second end of resistor R27 is connected to the anode of the light-emitting diode portion, and the second end of resistor R28 is grounded.

[0023] By adopting the above technical solution, and by setting current-limiting resistors R27 and R28 to perform voltage division and current control at the input terminal of the optocoupler, it can be ensured that the internal light-emitting diode of the optocoupler works reliably under a stable current, avoiding damage caused by unstable input signal amplitude or overdrive, thereby improving the reliability and long-term stability of the signal isolation process.

[0024] In summary, this application includes at least one of the following beneficial technical effects: This application constructs a hierarchical driving structure consisting of a signal isolation module, a multi-stage amplification and level conversion module, and a push-pull power amplifier module, forming a switching device driving circuit that possesses both anti-interference capabilities and strong driving output capabilities. The technical solution first utilizes the signal isolation module to achieve electrical decoupling between the control signal and the power loop, effectively blocking ground loop interference and ensuring the stability of the upstream control system. Subsequently, a multi-stage cascaded transistor amplification circuit inverts the isolated control signal and boosts its voltage level, transforming the originally weak ground-referenced signal into a high-amplitude signal suitable for driving the power device. Finally, the push-pull power amplifier module employs a complementary transistor pair structure, working with positive and negative power rails to form a positive and negative swing driving output, providing high-current push-pull capability to ensure that the gate capacitor of the high-power switching device completes charging and discharging in a very short time. It not only improves the driving speed and significantly reduces energy loss during the switching process, but also enhances the integrity of conduction and turn-off, avoiding false turn-on or incomplete turn-on caused by insufficient gate voltage. This effectively improves the overall conversion efficiency, thermal stability and device reliability of the system, and comprehensively addresses the key issues raised in the background technology, such as insufficient driving capability, low switching efficiency and limited device life. Attached Figure Description

[0025] Figure 1 This is a flowchart of an isolation drive circuit for a switching device according to one embodiment of this application.

[0026] Figure 2 This is a partial circuit structure diagram of an isolation drive circuit for a switching device according to one embodiment of this application.

[0027] Explanation of reference numerals in the attached diagram: 1. Signal isolation module; 2. Multi-stage amplification and level conversion module; 3. Push-pull power amplifier module; 4. Overcurrent protection module. Detailed Implementation

[0028] The present application will be further described in detail below with reference to the accompanying drawings.

[0029] In one embodiment, such as Figure 1-2 As shown, this application discloses a switching device isolation drive circuit, which is applied to the gate drive control of switching devices. The switching device isolation drive circuit includes a signal isolation module 1, a multi-stage amplification and level conversion module 2, and a push-pull power amplification module 3. The signal input terminal of the signal isolation module 1 is used to receive control signals, and the signal output terminal of the signal isolation module 1 is connected to the signal input terminal of the multi-stage amplification and level conversion module 2. The multi-stage amplification and level conversion module 2 includes a transistor cascade unit, which is used to invert and amplify the control signal output by the signal isolation module 1 and perform level conversion. The signal output terminal of the multi-stage amplification and level conversion module 2 is connected to the controlled terminal of the push-pull power amplifier module 3. The push-pull power amplifier module 3 includes at least one set of complementary driving transistor units. The set of complementary driving transistor units is used to convert the control signal into positive and negative driving voltages and output them between the gate and source of the switching device to realize the saturation conduction or reliable turn-off of the switching device.

[0030] In this embodiment, the signal input terminal of the signal isolation module 1 is connected to the output of the external control system to receive the original control signal, which is typically a logic level referenced to ground. After receiving the control signal, the signal isolation module 1 transmits it from the control side to the drive side via photoelectric conversion through optocouplers or other electrical isolation methods. Its signal output terminal serves as the signal input source for the multi-stage amplification and level conversion module 2, thereby structurally achieving electrical isolation between the control terminal and the power drive circuit, preventing high-voltage interference or faults from flowing back to the control side. In the multi-stage amplification and level conversion module 2, the transistor cascade unit consists of multiple stages of transistors. The output of each stage transistor is connected to the input of the next stage transistor, forming a sequential amplification path. The input terminal of this module receives the low-level control signal output from the signal isolation module 1. Through stage-by-stage amplification and inversion, it not only enhances the signal's driving capability but also raises its level from a ground-referenced logic level to a high-amplitude control level referenced to the positive and negative power supplies, thus achieving level conversion of the control signal. The final output of the transistor cascade unit serves as the controlled input signal of the push-pull power amplifier module 3, directly determining the on / off state of the complementary driving transistors in the subsequent push-pull structure. The push-pull power amplifier module 3 contains at least one set of complementary driving transistor units composed of NPN and PNP transistors. The two transistors in this structure are controlled by positive or negative control signals, respectively. When the control signal is high, the PNP transistor is turned on, and its output is pulled towards the positive voltage rail; conversely, when the control signal is low, the NPN transistor is turned on, and its output is pulled towards the negative voltage rail. Therefore, the push-pull power amplifier module 3 can generate a positive-negative switching driving voltage at its output under the drive of the control signal, thereby achieving bidirectional voltage drive between the gate and source of the switching device. This structure ensures that the switching device receives sufficient positive driving voltage when it needs to be turned on, and applies a stable negative voltage when it needs to be turned off, thus enabling fast and reliable device turn-on and turn-off. Simultaneously, it suppresses false turn-on caused by the Miller capacitance effect, improving the switching speed, energy efficiency, and safety of the entire drive system.

[0031] Furthermore, such as Figure 2As shown, a set of complementary driving transistor units includes NPN transistor V11, NPN transistor V12, PNP transistor V13 and PNP transistor V14. The base of NPN transistor V11 is connected to the signal output terminal of the multi-stage amplification and level conversion module 2. The collector of NPN transistor V11 is connected to the positive power supply. The emitter of NPN transistor V11 is connected to the base of PNP transistor V13. The collector of PNP transistor V13 is connected to the negative power supply. The emitter of PNP transistor V13 is connected to the gate terminal of the switching device. The base of PNP transistor V14 is connected to the signal output terminal of multi-stage amplification and level conversion module 2. The collector of PNP transistor V14 is connected to the negative power supply. The emitter of PNP transistor V14 is connected to the base of NPN transistor V12. The collector of NPN transistor V12 is connected to the positive power supply. The emitter of NPN transistor V12 and the emitter of PNP transistor V13 are connected to the gate terminal of the switching device. A push-pull output node is formed between the emitter of PNP transistor V12 and the emitter of NPN transistor V13. This node is used to alternately turn on PNP transistor V12 and NPN transistor V13 when the control signal is at different levels, so that the push-pull output node outputs positive and negative drive voltages to drive the gate of the switching device.

[0032] In this embodiment, the base of the NPN transistor V11 is directly connected to the signal output terminal, the collector is connected to the positive power supply, and the emitter is connected to the base of the PNP transistor V13. This path constitutes a control channel for the positive transmission of the control signal to the PNP transistor V13. The conduction of the NPN transistor V11 causes the PNP transistor V13 to conduct, and then its emitter outputs the potential on the negative power supply side through its internal transmission path to the push-pull output node shared with the emitter of the NPN transistor V12, i.e., the gate terminal of the switching device, thereby realizing negative voltage drive output. Meanwhile, the base of PNP transistor V14 also receives the same control signal, its collector is connected to the negative power supply, and its emitter is connected to the base of NPN transistor V12, forming a reverse drive path for the control signal. When the control signal is at the corresponding level that turns on PNP transistor V14, its emitter applies a negative power supply potential to the base of NPN transistor V12. If the control logic is valid at this time, NPN transistor V12 turns on, its collector is connected to the positive power supply, and its emitter transmits the positive power supply potential to the push-pull output node, i.e., the gate of the switching device, realizing forward drive. Therefore, the emitters of NPN transistor V12 and PNP transistor V13 share the same output node in structure. Under different input control levels, this node is turned on by either NPN transistor V12 or PNP transistor V13 to output a positive or negative drive voltage, completing the push-pull drive of the switching device gate. This mirror-symmetric complementary structure can alternately establish a low-impedance conduction path from the positive or negative power supply to the gate of the switching device under logic high and low levels. This not only improves the drive current capability and ensures rapid charging and discharging of the gate charge, but also effectively enhances the anti-interference capability and signal overshoot absorption capability, thereby achieving stable and reliable control of high-power switching devices in high-frequency and high-speed operating scenarios.

[0033] Furthermore, such as Figure 2 As shown, the push-pull power amplifier module 3 also includes diodes D15 and D16. The anode of diode D15 is connected to the emitter of PNP transistor V14, and the cathode of diode D15 is connected to the push-pull output node to enable conduction when the voltage of the push-pull output node is lower than the emitter potential of PNP transistor V14, thereby limiting the damage to the base of NPN transistor V12 caused by negative overvoltage. The anode of diode D16 is connected to the push-pull output node, and the cathode of diode D16 is connected to the emitter of NPN transistor V11 to enable conduction when the voltage of the push-pull output node is higher than the emitter potential of NPN transistor V11, thereby preventing control signal overshoot.

[0034] In this embodiment, diodes D15 and D16 form protection channels with the emitters of PNP transistor V14 and NPN transistor V11, respectively, to construct a voltage clamping path to absorb any abnormal voltage that may occur at the drive output terminal. Specifically, the anode of diode D15 is connected to the emitter of PNP transistor V14, meaning its internal side is the negative power supply side, while the cathode is connected to the push-pull output node, where the emitters of PNP transistor V13 and NPN transistor V12 are common. When the potential of the push-pull output node drops below the emitter potential of PNP transistor V14 due to load inductiveity or switching transients, diode D15 will conduct due to forward bias. At this time, the negative power supply potential is applied in reverse to the push-pull output node through the diode, effectively limiting further voltage drop at the node and preventing base over-surge breakdown or gate drive circuit instability of NPN transistor V12 due to negative overvoltage, thereby achieving voltage clamping protection in the negative voltage direction. On the other hand, the anode of diode D16 is directly connected to the push-pull output node, and the cathode is connected to the emitter of NPN transistor V11, whose emitter potential corresponds to the positive power supply voltage. When the push-pull output node is affected by factors such as control signal interference or loop induction, and the potential rises above the emitter level of NPN transistor V11, diode D16 is forward biased and conducts. At this time, the excess forward overvoltage of the push-pull output node will be discharged to the positive power supply side through this diode, suppressing current backflow caused by overshoot or abnormal conduction of transistor V11, thereby protecting the stability of the upper-stage amplifier and the entire output channel. Therefore, diodes D15 and D16 constitute a clamping protection mechanism for the positive and negative limit voltages of the push-pull output node. Under edge voltage changes during the push-pull output process, a discharge path can be quickly established, effectively preventing overshoot and drop of the drive voltage, ensuring the integrity of the push-pull output waveform and the electrical safety of the driving devices, and further improving the anti-interference capability and long-term stability of the entire isolated drive circuit in high-frequency, high-power applications.

[0035] Furthermore, such as Figure 2 As shown, the push-pull power amplifier module 3 also includes diode D13, diode D14 and filter capacitor C24. Diodes D13 and D14 are connected in reverse series between the gate and source of the switching device to limit the positive and negative driving voltage between the gate and source, preventing the gate voltage of the switching device from exceeding the corresponding allowable range. The series connection formed by diodes D13 and D14 after being connected in reverse series is connected in parallel with filter capacitor C24 to absorb spike interference in the output signal of push-pull power amplifier module 3.

[0036] In this embodiment, diodes D13 and D14 form a limiting protection structure. They are connected in reverse series and then bridging the gate and source of the switching device. Specifically, the anode of D13 is connected to the source of the switching device, the cathode to the cathode of D14, and the anode of D14 to the gate of the switching device, thus forming a clamping pair with opposing positive and negative conduction thresholds. When the drive voltage of the push-pull output node exceeds a preset range, surpassing the conduction voltage threshold of D13 or D14, the corresponding diode will enter a forward conduction state, quickly releasing the overvoltage charge to the source, blocking further rise or fall of the gate potential, and preventing the drive signal from causing breakdown of the gate oxide layer of the switching device or mis-conduction due to abnormal voltage. This voltage clamping structure can effectively control the voltage change between the gate and source of the switching device within a safe range, ensuring that high-power devices are not affected by voltage spikes during high-frequency switching. Furthermore, the filter capacitor C24 is connected in parallel with the reverse series structure formed by diodes D13 and D14, with its two electrodes connected between the gate and source, forming a symmetrical damping network. When the output edge of the push-pull power amplifier module 3 changes drastically, the filter capacitor C24 can quickly absorb and weaken high-frequency interference components in the drive signal and smooth the output waveform. Especially during the rapid turn-on and turn-off transition phase, it can suppress voltage ringing caused by wiring parasitic inductance and drive output surges, thereby avoiding noise interference to other control loops or power modules in the system. This limiting and absorption composite network together constructs a voltage regulation protection mechanism for the gate port of the switching device, effectively improving the electrical reliability and long-term operational stability of the gate drive system while ensuring signal integrity.

[0037] Furthermore, such as Figure 2 As shown, the multi-stage amplification and level conversion module 2 includes a transistor cascade unit composed of PNP transistor V3, PNP transistor V5 and NPN transistor V7 connected in sequence. The base of PNP transistor V3 is connected to the signal output terminal of signal isolation module 1, the collector of PNP transistor V3 is connected to the base of PNP transistor V5, and the emitter of PNP transistor V3 is connected to the positive power supply. The collector of PNP transistor V5 is connected to the base of NPN transistor V7, and the emitter of PNP transistor V5 is connected to the positive power supply; the emitter of NPN transistor V7 is connected to the negative power supply, and the collector of NPN transistor V7 serves as the signal output terminal of the multi-stage amplification and level conversion module 2.

[0038] In this embodiment, the base of PNP transistor V3 is directly connected to the signal output terminal of signal isolation module 1, so that the control signal is first received by PNP transistor V3 after optocoupler isolation, and its base responds to the input control level. If the control signal is low, V3 is turned on. The emitter of PNP transistor V3 is connected to the positive power supply, and its collector is connected to the base of the next stage PNP transistor V5. When V3 is turned on, its collector potential drops, thereby driving the base of V5 into the conducting state. The emitter of PNP transistor V5 is also connected to the positive power supply. When its base is low relative to the emitter, it will be turned on. Its collector is further connected to the base of NPN transistor V7, meaning that V5 will drive V7 to be turned on after it is turned on. The emitter of NPN transistor V7 is connected to the negative power supply, and its base receives the initial input signal through the collector of V5. If the bias threshold between the base and emitter of V7 is reached, it will be turned on and output an amplified signal. Ultimately, the collector of NPN transistor V7 forms the signal output terminal of the multi-stage amplification and level conversion module 2. During the stage-by-stage amplification process of the multi-stage transistors, the input signal is effectively inverted and superimposed with driving capability, converting the low-level optocoupler output signal into a high-speed, high-current control signal capable of driving the push-pull power stage. The entire cascaded structure consists of PNP transistors V3 and V5, and NPN transistor V7, forming a top-down, stage-by-stage current amplification path. This achieves the conversion of the control signal from the low-power optocoupler output to a high-driving-capability gate drive signal, completing both level boosting and improving signal response speed and load driving capability, thus ensuring reliable driving of the subsequent push-pull power amplifier module 3.

[0039] Furthermore, such as Figure 2 As shown, the multi-stage amplification and level conversion module 2 also includes resistors R38 and R39. The first end of resistor R39 is connected to the positive power supply, the second end of resistor R39 is connected to the first end of resistor R38, the second end of resistor R38 is connected to the collector of NPN transistor V7, and the common node between the second end of resistor R39 and the first end of resistor R38 serves as the signal output terminal of the multi-stage amplification and level conversion module 2.

[0040] In this embodiment, the multi-stage amplification and level conversion module 2 further includes resistors R38 and R39. The first end of resistor R39 is connected to the positive power supply to provide a pull-up potential. The second end of resistor R39 is directly connected to the first end of resistor R38, forming a voltage divider and current-limiting path. The second end of resistor R38 is connected to the collector of NPN transistor V7. When NPN transistor V7 is turned on, its collector voltage is pulled low, resulting in a voltage drop across resistor R38, causing the potential of the common node connected between R39 and R38 to decrease accordingly. When V7 is turned off, R39 pulls up the node voltage through its connection to the positive power supply. Therefore, this common node can output corresponding high and low level signals depending on whether V7 is on or off, forming an effective control output. This achieves a smooth transition of the collector level of V7 and also provides some current-limiting protection. This node serves as the signal output terminal of this module, providing drive control for the subsequent push-pull power amplifier module 3.

[0041] Furthermore, such as Figure 2 As shown, a switching device isolation drive circuit also includes an overcurrent protection module 4. The overcurrent protection module 4 is used to detect the overcurrent signal in the circuit where the switching device is located. The multi-stage amplification and level conversion module 2 also includes a resistor R32. The first end of the resistor R32 is connected to the collector of the PNP transistor V3, and the second end of the resistor R32 is connected to the base of the PNP transistor V5. The common node between the second end of the resistor R32 and the base of the PNP transistor V5 is connected to the control output terminal of the overcurrent protection module 4, so as to cut off the drive signal and clamp the output of the push-pull power amplifier module 3 to a negative voltage level when an overcurrent occurs, so as to prevent damage to the switching device.

[0042] In this embodiment, the switching device isolation drive circuit is further provided with an overcurrent protection module 4. This module is used to monitor the current changes in the switching device's operating circuit in real time and generate a control signal to provide protection when an overcurrent event is detected. A resistor R32 is added to the multi-stage amplification and level conversion module 2. The first end of resistor R32 is connected to the collector of PNP transistor V3 to receive the amplified signal output by V3, and the second end is connected to the base of PNP transistor V5, forming a signal transmission path between V3 and V5. Simultaneously, the common node between the second end of resistor R32 and the base of PNP transistor V5 is connected to the control output terminal of the overcurrent protection module 4 to inject the protection signal into this node. When an overcurrent fault occurs, the overcurrent protection module 4 outputs a low-level or negative voltage control signal, forcing the PNP transistor V5 to turn off, thereby interrupting the signal transmission link of the multi-stage amplification and level conversion module 2. This causes the subsequent push-pull power amplifier module 3 to lose its effective drive signal and enter the cutoff state. At the same time, it clamps its output terminal to a negative voltage potential to prevent the switching device from thermally breaking down or being damaged at the gate due to overcurrent, thus improving the safety and reliability of the entire machine.

[0043] Furthermore, such as Figure 2 As shown, the overcurrent protection module 4 includes a latch control chip D1, a resistor R4, and a capacitor C3. The signal output terminal of the latch control chip D1 is connected to the first terminal of the resistor R4 and the first terminal of the capacitor C3, respectively. The common node between the second terminal of the resistor R32 and the base of the PNP transistor V5 is connected to the second terminal of the resistor R4 and the second terminal of the capacitor C3, respectively.

[0044] In this embodiment, the overcurrent protection module 4 includes a latch control chip D1, a resistor R4, and a capacitor C3. It generates and maintains a protection control signal after detecting an overcurrent signal to provide continuous protection for the drive circuit. The signal output terminal of the latch control chip D1 is connected to the first terminal of resistor R4 and the first terminal of capacitor C3, forming a delay filter branch for the output signal to enhance the stability of the protection signal. The second terminal of resistor R4 and the second terminal of capacitor C3 are connected to a common node between the second terminal of resistor R32 and the base of PNP transistor V5, allowing this node to receive control signals from the latch control chip D1. When an overcurrent event occurs, the latch control chip D1 outputs a high-level or negative voltage signal, which is applied to the common node via resistor R4, causing PNP transistor V5 to enter a cutoff state, interrupting the drive path and clamping the output voltage. Capacitor C3 helps maintain the protection state for a short time, ensuring sufficient protection response time even if the overcurrent signal disappears instantaneously, thereby effectively avoiding the risk of gate surge and thermal breakdown of high-power switching devices caused by instantaneous high current.

[0045] Furthermore, such as Figure 2As shown, the signal isolation module 1 includes an optocoupler N1, which includes a light-emitting diode (LED) section and a transistor section. The anode of the LED section is used to receive control signals, and the cathode of the LED section is grounded. The first conducting terminal of the transistor section is connected to the positive power supply, and the second conducting terminal of the transistor section is connected to the signal input terminal of the multi-stage amplification and level conversion module 2.

[0046] In this embodiment, the anode of the light-emitting diode receives the control signal, and the cathode is grounded. When a control signal is input, the light-emitting diode triggers the transistor to conduct. Its first conducting terminal is connected to the positive power supply, and its second conducting terminal is connected to the signal input terminal of the multi-stage amplification and level conversion module 2, thereby realizing the isolated transmission of the control signal.

[0047] Furthermore, such as Figure 2 As shown, the signal isolation module 1 also includes resistors R27 and R28. The common node between the first end of resistor R27 and the first end of resistor R28 serves as the signal input terminal of the signal isolation module 1 for receiving control signals. The second end of resistor R27 is connected to the anode of the light-emitting diode section, and the second end of resistor R28 is grounded.

[0048] In this embodiment, by setting current-limiting resistors R27 and R28 to perform voltage division and current control at the input terminal of the optocoupler, it can be ensured that the internal light-emitting diode of the optocoupler works reliably under a stable current, avoiding damage caused by unstable input signal amplitude or overdrive, thereby improving the reliability and long-term stability of the signal isolation process.

[0049] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A switching device isolation drive circuit, characterized in that, The isolation drive circuit for switching devices, which is used in the gate drive control of switching devices, includes a signal isolation module, a multi-stage amplification and level conversion module, and a push-pull power amplification module. The signal input terminal of the signal isolation module is used to receive control signals, and the signal output terminal of the signal isolation module is connected to the signal input terminal of the multi-stage amplification and level conversion module. The multi-stage amplification and level conversion module includes a transistor cascade unit, which is used to invert and amplify the control signal output by the signal isolation module and perform level conversion. The signal output terminal of the multi-stage amplification and level conversion module is connected to the controlled terminal of the push-pull power amplifier module. The push-pull power amplifier module includes at least one set of complementary driving transistor units, which are used to convert the control signal into positive and negative driving voltages and output them between the gate and source of the switching device to achieve saturation conduction or reliable turn-off of the switching device.

2. The isolation drive circuit for a switching device according to claim 1, characterized in that, The set of complementary driving transistor units includes NPN transistor V11, NPN transistor V12, PNP transistor V13, and PNP transistor V14. The base of NPN transistor V11 is connected to the signal output terminal of the multi-stage amplification and level conversion module. The collector of NPN transistor V11 is connected to the positive power supply. The emitter of NPN transistor V11 is connected to the base of PNP transistor V13. The collector of PNP transistor V13 is connected to the negative power supply. The emitter of PNP transistor V13 is connected to the gate terminal of the switching device. The base of the PNP transistor V14 is connected to the signal output terminal of the multi-stage amplification and level conversion module. The collector of the PNP transistor V14 is connected to the negative power supply. The emitter of the PNP transistor V14 is connected to the base of the NPN transistor V12. The collector of the NPN transistor V12 is connected to the positive power supply. The emitters of the NPN transistor V12 and the PNP transistor V13 are connected to the gate terminal of the switching device. A push-pull output node is formed between the emitter of the PNP transistor V12 and the emitter of the NPN transistor V13. This node is used to alternately turn on the PNP transistor V12 and the NPN transistor V13 when the control signal is at different levels, so that the push-pull output node outputs positive and negative driving voltages to drive the gate of the switching device.

3. The isolation drive circuit for a switching device according to claim 2, characterized in that, The push-pull power amplifier module further includes diodes D15 and D16. The anode of diode D15 is connected to the emitter of PNP transistor V14, and the cathode of diode D15 is connected to the push-pull output node. This allows the diode to conduct when the voltage at the push-pull output node is lower than the emitter potential of PNP transistor V14, thus limiting negative overvoltage from damaging the base of NPN transistor V12. The anode of diode D16 is connected to the push-pull output node, and the cathode of diode D16 is connected to the emitter of NPN transistor V11. This allows the diode to conduct when the voltage at the push-pull output node is higher than the emitter potential of NPN transistor V11, thus preventing overshoot of the control signal.

4. The isolation drive circuit for a switching device according to claim 2, characterized in that, The push-pull power amplifier module also includes diode D13, diode D14 and filter capacitor C24. Diode D13 and diode D14 are connected in reverse series between the gate and source of the switching device to limit the positive and negative driving voltage between the gate and source, preventing the gate voltage of the switching device from exceeding the corresponding allowable range. The series connection formed by the reverse series connection of diodes D13 and D14 is connected in parallel with the filter capacitor C24 to absorb spike interference in the output signal of the push-pull power amplifier module.

5. The isolation drive circuit for a switching device according to claim 1, characterized in that, The multi-stage amplification and level conversion module includes a transistor cascade unit composed of PNP transistor V3, PNP transistor V5 and NPN transistor V7 cascaded in sequence. The base of PNP transistor V3 is connected to the signal output terminal of the signal isolation module, the collector of PNP transistor V3 is connected to the base of PNP transistor V5, and the emitter of PNP transistor V3 is connected to the positive power supply. The collector of the PNP transistor V5 is connected to the base of the NPN transistor V7, and the emitter of the PNP transistor V5 is connected to the positive power supply; the emitter of the NPN transistor V7 is connected to the negative power supply, and the collector of the NPN transistor V7 serves as the signal output terminal of the multi-stage amplification and level conversion module.

6. The isolation drive circuit for a switching device according to claim 5, characterized in that, The multi-stage amplification and level conversion module also includes resistors R38 and R39. The first end of resistor R39 is connected to the positive power supply, and the second end of resistor R39 is connected to the first end of resistor R38. The second end of resistor R38 is connected to the collector of NPN transistor V7. The common node between the second end of resistor R39 and the first end of resistor R38 serves as the signal output terminal of the multi-stage amplification and level conversion module.

7. The isolation drive circuit for a switching device according to claim 5, characterized in that, The isolation drive circuit for the switching device further includes an overcurrent protection module, which is used to detect overcurrent signals in the circuit where the switching device is located. The multi-stage amplification and level conversion module also includes a resistor R32. The first end of the resistor R32 is connected to the collector of the PNP transistor V3, and the second end of the resistor R32 is connected to the base of the PNP transistor V5. The common node between the second end of the resistor R32 and the base of the PNP transistor V5 is connected to the control output terminal of the overcurrent protection module, so as to cut off the drive signal and clamp the output of the push-pull power amplifier module to a negative voltage level when an overcurrent occurs, thereby preventing damage to the switching device.

8. The isolation drive circuit for a switching device according to claim 7, characterized in that, The overcurrent protection module includes a latch control chip D1, a resistor R4, and a capacitor C3. The signal output terminal of the latch control chip D1 is connected to the first terminal of the resistor R4 and the first terminal of the capacitor C3, respectively. The common node between the second terminal of the resistor R32 and the base of the PNP transistor V5 is connected to the second terminal of the resistor R4 and the second terminal of the capacitor C3, respectively.

9. The isolation drive circuit for a switching device according to claim 1, characterized in that, The signal isolation module includes an optocoupler N1, which comprises a light-emitting diode (LED) portion and a transistor portion. The anode of the LED portion is used to receive control signals, and the cathode of the LED portion is grounded. The first conducting terminal of the transistor portion is connected to the positive power supply, and the second conducting terminal of the transistor portion is connected to the signal input terminal of the multi-stage amplification and level conversion module.

10. The isolation drive circuit for a switching device according to claim 9, characterized in that, The signal isolation module further includes resistors R27 and R28. The common node between the first end of resistor R27 and the first end of resistor R28 serves as the signal input terminal of the signal isolation module for receiving control signals. The second end of resistor R27 is connected to the anode of the light-emitting diode portion, and the second end of resistor R28 is grounded.

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