Switching power device short circuit protection structure for realizing low turn-off overshoot

Abstract

The invention belongs to the related technical field of short-circuit protection of power electronic equipment, and discloses a short-circuit protection structure of a switching power device for realizing low turn-off overshoot. A grid resistance voltage detection circuit detects grid resistance voltage of the device and outputs detection voltage VG; the conduction voltage drop detection circuit detects the conduction voltage drop when the device is conducted and outputs a detection voltage VD, and the device voltage detection circuit detects the device voltage and outputs a detection voltage VH; the short circuit judgment circuit judges whether a short circuit fault occurs or not according to the voltage VG and the voltage VD and outputs a control signal SSC; the turn-off judgment circuit judges whether a device needs to be turned off according to the SSC and the VH and outputs a control signal SSD; and the gate driving module is used for judging the device state according to the SSC and the SSD and controlling the device driving voltage. Through the short-circuit protection structure, the response speed of a short-circuit fault can be improved, and a proper time switch-off device can be selected, so that short-circuit overshoot is effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of short-circuit protection of power electronic devices, and more particularly relates to a short-circuit protection structure of a switching power device for realizing low turn-off overshoot. BACKGROUND

[0002] With the rapid development of new energy and new power systems, power electronic devices such as converters have higher requirements in terms of power density, efficiency and reliability. As the core component of power electronic devices, the safe and controllable operation of power switching devices has become a key link restricting the performance of the system.

[0003] Under the premise that the rated capacity of the power switching device is given, engineering applications need to improve the voltage utilization rate of the device under the condition of meeting the insulation and thermal design boundaries. However, practice shows that the turn-off voltage overshoot under short-circuit conditions is the main factor limiting the improvement of the voltage utilization rate of the power switching device, and the current data manual usually suggests that the actual use voltage is about 75% of the rated value, resulting in that the design redundancy is too large, and the volume and cost are difficult to further reduce. The short-circuit protection in the drive board is the primary protection mechanism after the short-circuit of the device, and its detection scheme and turn-off strategy directly affect the short-circuit current peak and turn-off overvoltage. However, the current short-circuit protection mechanism generally has problems such as short-circuit fault detection delay and unreasonable turn-off time selection, which still causes a large short-circuit overshoot.

[0004] Therefore, how to improve the response speed of short-circuit faults and select the appropriate time to turn off the device so as to effectively reduce the short-circuit overshoot is a technical problem to be solved at present. SUMMARY

[0005] In view of the above defects or improvement needs of the prior art, the present application provides a short-circuit protection structure of a switching power device for realizing low turn-off overshoot, which aims to improve the response speed of short-circuit faults and select the appropriate time to turn off the device so as to effectively reduce the short-circuit overshoot.

[0006] To achieve the above-mentioned purpose, a short-circuit protection structure of a switching power device for realizing low turn-off overshoot is provided, which comprises a detection module, a control module and a gate drive module, wherein, The detection module comprises a gate resistor voltage detection circuit, a conduction voltage drop detection circuit and a device voltage detection circuit; the gate resistor voltage detection circuit is used for detecting the gate resistor voltage of the device and outputting a detection voltage V G When the device enters a fully conducting state, V G <V ref1 , otherwise, V G ≥V ref1 , V ref1a reference voltage for judging the full conduction state of the device; the conduction voltage drop detection circuit is used for detecting the conduction voltage drop of the device when the device is in conduction and outputting a detection voltage V D , when the device enters the full conduction state, V D is equal to the conduction voltage drop, otherwise, V D is the ground voltage; the device voltage detection circuit is used for detecting the device voltage and outputting a detection voltage V H , the voltage V H is proportional to the device voltage; The control module comprises a short circuit judging circuit and a turn-off judging circuit, the short circuit judging circuit is used for judging whether a short circuit fault occurs according to the voltage V G and the voltage V D and outputting a control signal S SC , when V G <V ref1 and V D ≥V ref2 , V ref2 is a reference voltage for judging the occurrence of the desaturation of the device and judging the occurrence of the short circuit fault; the turn-off judging circuit is used for judging whether the device needs to be turned off according to the signal S SC and the voltage V H and outputting a control signal S SD , when the signal S SC indicates the occurrence of the short circuit fault and V H ≥V ref3 , V ref3 is an upper limit of the safe operation voltage of the device, and the device needs to be turned off is judged; The gate drive module is used for judging the state of the device according to the signals S SC and S SD and controlling the device driving voltage, when the device does not have a fault, the device driving voltage is only controlled by the normal driving signal of the device, when the device has a short circuit fault but does not need to be turned off, the device driving voltage is reduced, and when the device has a short circuit fault and needs to be turned off, the device is turned off.

[0007] Overall, compared with the prior art, the above technical scheme conceived by the present application mainly has the following beneficial effects: The application collects the gate resistance voltage through the gate resistance voltage detection circuit, identifies whether the device enters the fully conducting state based on the change of the gate resistance voltage, collects the conducting voltage drop of the device through the conducting voltage drop detection circuit, identifies whether the device occurs desaturation phenomenon based on the change of the conducting voltage drop, combines the detection results of the gate resistance voltage detection circuit and the detection results of the conducting voltage drop detection circuit to determine whether the short circuit fault occurs, and when the device enters the fully conducting state and still occurs desaturation, it indicates that the short circuit fault occurs, so that the short circuit fault can be accurately and quickly identified, and misjudgment is avoided. Moreover, the device voltage is collected through the device voltage detection circuit, the detection results of the device voltage detection circuit and the determination results of the short circuit determination circuit are combined to determine the short circuit shutdown point, when the short circuit fault occurs and the device voltage rises close to the device operating voltage, it indicates that the carrier concentration in the device is low at this time, the device characteristics are relatively stable, the shutdown current rate is controllable, the device can be shut down and the shutdown overshoot is small. Overall, based on the short circuit protection structure of the switching power device mentioned in the application, the response speed of the short circuit fault can be improved and the device can be shut down at the appropriate time, so that the short circuit overshoot is effectively reduced. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a structure schematic diagram of the short circuit protection structure of the switching power device in an embodiment of the application.

[0009] Figure 2 is a structure schematic diagram of the power switching device in an embodiment of the application.

[0010] Figure 3 is a circuit diagram of the detection module in an embodiment of the application.

[0011] Figure 4 is a circuit diagram of the control module in an embodiment of the application.

[0012] Figure 5 is a circuit diagram of the gate drive module in an embodiment of the application.

[0013] Figure 6 is the hard opening short circuit measurement result after adopting the conventional desaturation protection.

[0014] Figure 7 is the hard opening short circuit measurement result after adopting the short circuit protection structure of the application.

[0015] Figure 8 is the load short circuit measurement result after adopting the conventional desaturation protection.

[0016] Figure 9 is the load short circuit measurement result after adopting the short circuit protection structure of the application. DETAILED DESCRIPTION

[0017] In order to make the objects, technical solutions and advantages of the present application clearer, the following further describes the present application with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0018] In a first aspect, the present application claims a short-circuit protection structure of a switching power device for realizing low turn-off overshoot.

[0019] As Figure 1 shown is a structure schematic diagram of a short-circuit protection structure of a switching power device in an embodiment of the present application. As Figure 2 shown is a structure schematic diagram of a power switching device in an embodiment, taking IGBT as an example, the gate electrode of which is connected with a gate electrode resistance L g , and a device driving voltage is applied to the power switching device through the gate electrode resistance L g .

[0020] The short-circuit protection structure of the switching power device includes a detection module, a control module and a gate electrode driving module. The detection module includes a gate electrode resistance voltage detection circuit, a conduction voltage drop detection circuit and a device voltage detection circuit. The control module includes a short-circuit determination circuit and a turn-off determination circuit.

[0021] The gate electrode resistance voltage detection circuit is used for detecting the gate electrode resistance voltage of the device and outputting a detection voltage V G , when the device enters a fully conducting state, V G < V ref1 , otherwise, V G ≥ V ref1 , V ref1 is a reference voltage for determining the fully conducting state of the device. For the power switching device, the reference voltage V ref1 for determining the fully conducting state of the device can be set, and whether the device enters the fully conducting state is identified based on the change of the gate electrode resistance voltage by collecting the gate electrode resistance voltage.

[0022] The conduction voltage drop detection circuit is used for detecting the conduction voltage drop of the device when it is conducting and outputting a detection voltage V D , when the device enters the fully conducting state, V D is equal to the conduction voltage drop, otherwise, V D is a ground voltage. For the power switching device, if a short-circuit fault occurs, the device will have a desaturation phenomenon, and its conduction voltage drop will rise sharply, therefore, a reference voltage V ref2 for determining whether the device has the desaturation phenomenon can be set, and whether the device has the desaturation phenomenon is identified based on the change of the conduction voltage drop by collecting the conduction voltage drop.

[0023] The device voltage detection circuit is used to detect the device voltage and output the detected voltage V. H Voltage V H It is proportional to the device voltage. For power switching devices, when a short-circuit fault occurs, excess carriers inside the device are gradually discharged as the device voltage rises. Turning off when the internal carrier concentration is high reduces the controllability of the short-circuit current decrease rate, leading to an increase in the peak turn-off voltage. Therefore, a short-circuit turn-off threshold V can be set. ref3 By collecting the device voltage, when it exceeds the safety shutdown threshold V ref3 When this occurs, a short-circuit shutdown is triggered.

[0024] The short-circuit detection circuit is used to determine the short circuit based on the voltage V. G and voltage V D Determine if a short circuit fault has occurred and output a control signal S. SC When V G <V ref1 And V D ≥V ref2 At that time, V ref2 A reference voltage is used to determine when a device desaturates, thus identifying a short-circuit fault. V G <V ref1 This indicates that the device has been fully turned on, V D ≥V ref2 This indicates that the device has desaturated. If desaturation occurs when the device is fully conducting, it indicates that a short circuit fault has occurred and safety protection measures need to be activated.

[0025] The shutdown determination circuit is used to determine the shutdown based on signal S. SC and voltage V H Determine whether the device needs to be turned off and output control signal S. SD When signal S SC Indicates a short circuit fault and V H ≥V ref3 At that time, V ref3 This is the short-circuit shutdown threshold for the device, used to determine whether a short-circuit shutdown with a low voltage peak is permissible. When the device is in a short-circuit fault and the device voltage exceeds its shutdown threshold, it indicates that a short-circuit shutdown can be performed.

[0026] The gate drive module is used to drive the gate according to the signal S. SC and S SD The device status is determined and the device drive voltage is controlled. When the device is not faulty, the device drive voltage is only controlled by the normal drive signal of the device. When the device has a short circuit fault but does not need to be turned off, the device drive voltage is reduced. When the device has a short circuit fault and needs to be turned off, the device is turned off.

[0027] As Figure 3 shown is a circuit diagram of the detection module in an embodiment of the application.

[0028] In an embodiment, the gate resistance voltage detection circuit 11 comprises: a differential amplifier OP1 and diodes D1 and D2, two inputs of the differential amplifier OP1 are connected to two ends of the device gate resistance L g respectively through the diodes D1 and D2, the two ends of the device gate resistance L g are denoted as R g-1 and R g-2 respectively, and an output of the differential amplifier OP1 outputs a detection voltage V G , wherein the detection voltage V G is equal to the voltage of the device gate resistance.

[0029] In an embodiment, the on-voltage drop detection circuit 12 comprises: a diode D3, a current-limiting resistor R1, a switch S1 and a gate driver GD3; a cathode of the diode D3 is connected to the collector C of the device, an anode is connected to one end of the current-limiting resistor R1 and a drain of the switch S1 respectively, a source of the switch S1 is grounded, the other end of the current-limiting resistor R1 is used for connecting a driving power source V CC , the gate driver GD3 is used for connecting a normal driving signal PWM of the device and inputting to the gate of the switch S1 after inverting operation, and a drain of the switch S1 outputs a detection voltage V D .

[0030] In the embodiment, the gate driver GD3 has a reverse output function; When the normal driving signal PWM of the device is high: the power device S0 is turned on, GD3 outputs low to make S1 off, during the period when the power device S0 is turned on and no desaturation occurs, when the on-voltage drop of S0 is less than V CC , the diode D3 is turned on, and the voltage V D is equal to the sum of the on-voltage drop V CE(sat) of S0 and the on-voltage drop V F of the diode D3, when S0 is turned on and desaturation occurs, the voltage drop rises to be greater than V CC , then D1 is cut off, and at this time, the voltage V D is equal to V CC . When the normal driving signal PWM of the device is low: the power device S0 is turned off, GD3 outputs low to make S1 turned on, D3 is cut off, and V D =0.

[0031] In an embodiment, the device voltage detection circuit 13 comprises voltage dividing resistors R2, R3 and voltage dividing capacitors C1, C2, the resistors R2, R3 are connected in series with C1 and R2 in parallel, and C2 and R3 in parallel, forming a voltage dividing structure, the voltage dividing ratio k = R3 / (R2+R3), and the output voltage V H is related to the device drain-source voltage V CE of the power device. H The relationship satisfies: V CE =k*V G .

[0032] As shown in Figure 4 is a circuit diagram of the control module in an embodiment of the application.

[0033] In an embodiment, the short circuit determination circuit comprises comparators CP1, CP2 and an AND operation device IC1; the inverting input terminal of the comparator CP1 is connected to the voltage V ref1 , the non-inverting input terminal is used to connect to the reference voltage V G , and the output terminal outputs a comparison level signal S D ; the non-inverting input terminal of the comparator CP2 is connected to the voltage V ref2 , the inverting input terminal is used to connect to the reference voltage V D , and the output terminal outputs a comparison level signal S G ; the AND operation device IC1 is used to connect to the signals S D and S SC and perform AND operation, and output a control signal S ref1 .

[0034] In this embodiment, when the power device S0 is turned off, the gate current is large, and the gate resistance voltage is large; when the power device S0 is turned on, the gate resistance voltage is also large in the transient state of turning on, and then the voltage drops to a lower value and enters the fully on state. Therefore, by setting the reference voltage V G , the voltage V ref1 is compared by the comparator CP1, when V G <V ref1 , it is determined that the power device S0 is in the fully on state, the comparator CP1 outputs a high level, S G =1, that is, S G =1 indicates that the power device has approached or reached the fully on state, otherwise, S G =0. In specific operation, the reference voltage V ref1 may be set as , where V DRV-ON is the turn-on driving voltage connected by the gate resistance, and V mil is the Miller plateau voltage of the device. After the power device is turned on and the device voltage drops to the fully on state, S G outputs a high level.

[0035] In the embodiment, when the power device S0 is off, V D =0, when the power device S0 is on and no desaturation occurs, the on voltage of the device is a smaller voltage value, i.e. V D is smaller, and when the power device S0 is on and desaturation occurs, the on voltage of the device instantaneously increases, i.e. V D is larger. Therefore, by setting the reference voltage V ref2 , the comparator CP2 compares the voltage V D and V ref2 , when V D ≥V ref2 , it is determined that the power device S0 has desaturated, the comparator CP2 outputs a high level, S D =1, i.e. S D =1 indicates that the current flowing through the power device at this time is large and desaturation occurs, otherwise, S D =0. In the specific operation, the reference voltage V ref2 may be set as , and V sat is the saturation voltage value of the power device under the rated drive voltage and twice the rated current I CM . When the power device desaturates, S D outputs a high level.

[0036] In the embodiment, the AND gate operator IC1 performs AND operation on the signal S G and the signal S D , only when S G =1 and S D =1, the AND gate operator IC1 outputs a high level, S SC =1, i.e. only when the device is in a fully on state and desaturation occurs, it indicates that a short circuit fault occurs. It should be noted that desaturation occurs in both the short circuit fault and the on transient state of the device, and if the occurrence of desaturation is directly used as the judgment standard of the short circuit fault, it is very likely that the on transient state of the device will also be considered as a short circuit fault, thus causing misjudgment. In the present application, the detection result of the gate resistor voltage detection circuit and the detection result of the on voltage drop detection circuit are combined to make the judgment, when the device enters a fully on state and still desaturates, it indicates that a short circuit fault occurs, thus the short circuit fault can be accurately and quickly identified, and misjudgment is avoided.

[0037] In an embodiment, the off judgment circuit includes a comparator CP3, an AND gate operator IC2 and a latch IC3; the non-inverting input end of the comparator CP3 is connected to the voltage V H , the inverting input end is used to connect to the reference voltage V ref3 , and the output end outputs a comparison level signal S H; the latch IC3 is used for latching the control signal S SC ; the AND gate operator IC3 is used for inputting the signal S H and the signal S SC latched by the latch IC3 and performing AND gate operation to output the control signal S SD .

[0038] In the embodiment, when the short circuit fault occurs and the device voltage continuously rises to a certain value, the concentration of the excess carriers in the device is low, at this time, the controllability of the turn-off rate of the short circuit current of the device is strong, and the peak value of the turn-off voltage is low. Therefore, by setting the short circuit turn-off point threshold V ref3 , the voltage V H is compared with V ref3 by the comparator CP3, when V H <V ref3 , it is determined whether the voltage of the power device S0 rises to the appropriate short circuit turn-off point, the comparator CP1 outputs low level, S H =0, that is, S H =0 indicates that the device of the power device is not suitable for short circuit turn-off, when V H ≥V ref3 , it is determined that the voltage of the power device S0 has risen to the appropriate short circuit turn-off point, the comparator CP1 outputs high level, S H =1, that is, S H =1 indicates that the device voltage of the power device has risen to the appropriate short circuit turn-off point. In the specific operation, the reference voltage V ref3 may be set as , wherein V BUS is the bus voltage.

[0039] In the embodiment, the AND gate operator IC2 is used for performing AND gate operation on the signal S H and the signal S SC , only when S H =1 and S SC =1, the AND gate operator IC2 outputs high level, S SD =1, that is, only when the short circuit fault occurs and the device voltage rises to the appropriate short circuit turn-off point, it indicates that the device needs to be turned off. It should be noted that if the device is directly turned off when the short circuit fault occurs, when the short circuit fault is the load short circuit fault, the device is directly turned off when the short circuit fault occurs, at this time, the device voltage is low, the carriers in the device have not been fully evacuated, and it is very likely to cause turn-off overshoot. In the present application, the detection result of the device voltage detection circuit and the determination result of the short circuit determination circuit are combined to determine whether the short circuit fault occurs and the device voltage rises to the appropriate short circuit turn-off point, at this time, the concentration of the carriers in the device is low, the characteristics of the device are stable, the turn-off current rate is controllable, the device can be turned off, and the turn-off overshoot is small.

[0040] As shown in Figure 5 is a circuit diagram of a gate drive module in an embodiment of the present application.

[0041] In an embodiment, the gate drive module comprises: gate drive chips GD1, GD2, NAND operator IC4, and OR operator IC5; the NAND operator IC4 is used to perform NAND operation on the negated signal of the normal drive signal PWM of the device and the control signal S SC , and input the result to the input end of the gate drive chip GD1, the output end of the gate drive chip GD1 is connected to the gate of the device; the OR operator IC4 is used to perform OR operation on the negated signal of the normal drive signal PWM of the device and the control signal S SD , and input the result to the input end of the gate drive chip GD2, the output end of the gate drive chip GD2 is connected to the emitter of the device; the output end of the gate drive chip GD1 and the output end of GD2 form the device drive voltage V DRV .

[0042] In the embodiment, when the device does not have short-circuit failure, S SC is low, S SD is low, IC4 outputs high level, IC5 follows the negated signal of the normal drive signal PWM, and the device drive voltage V DRV follows the change of the normal drive signal PWM; when the device has short-circuit failure but does not need to be shut down, S SC is high, S SD is low, IC4 follows the normal drive signal PWM, IC5 follows the negated signal of the normal drive signal PWM, and the device drive voltage V DRV follows the change of the normal drive signal PWM and is pulled down compared with when the device does not have short-circuit failure; when the device has short-circuit failure and needs to be shut down, S SC is high, S SD is high, IC4 follows the normal drive signal PWM, IC5 outputs high level, and the device drive voltage V DRV is pulled down to the device shut-down threshold.

[0043] In specific settings, the input power of GD1 is V CC and V EE , the input power of GD2 is GND and V EE , wherein V EE is negative level. In the normal drive process, GD1 outputs high level V CC , GD2 outputs low level VEE, the device drive voltage V DRV = V CC - V EE ; when S SCAfter the signal goes high, GD2 outputs a low level V. EE Switching to output high level GND, device drive voltage V DRV By V CC -V EE Reduce to V CC Suppressing further increase in short-circuit current; subsequently when S SD After becoming high, GD1 outputs a high level V. CC Switch to output low level V EE This causes the device drive voltage V to... DRV By V CC Switch to V EE Perform short-circuit shutdown.

[0044] For example, the input power supply of gate driver chip GD1 is 10V and -5V, and the input power supply of gate driver chip GD2 is 0V and -5V. When S SC After the signal goes high, GD2 switches from output low level -5V to output high level 0V, reducing the power device voltage from 15V to 10V to suppress further increase in short-circuit current. Then, when S... SD After the output level changes to high, the gate driver chip GD1 switches from output high level 10V to output low level -5V, causing the gate voltage of the power device to switch from 10V to -5V, thus performing short-circuit shutdown.

[0045] The feasibility and advancement of the short-circuit protection in this invention are verified through specific experiments. In the experiments, the gate driver chip was model 1EDN7512BXTSA1, the comparators were all LTC6752, and the diode D2 used in the forward voltage drop measurement was model RS1MWF, the switching transistor was model DMN6075, and the gate driver was model LMG1025. The instrumentation amplifier used in the gate resistance voltage detection was AD8429, and the voltage across the power device was proportionally reduced by a factor of 100 (k=1 / 100) in the device voltage detection. The AND gate model was model SN74LVC1G08, and the latch model was model SN74LVC1G175. The short-circuit test bus voltage was selected as 100V, and the power device used was the company's IKY75N120CH7 IGBT device. The above is only one verification method; those skilled in the art should understand that the low turn-off overshoot short-circuit protection circuit is not limited to the models mentioned above. In the experiment, V D V H V G S D S H S G S SC S SDand each signal point signal is measured by a low voltage differential probe TDDP1000 with a bandwidth of 1GHz, collector-emitter voltage V CE measured by a THDP0200 with a bandwidth of 200MHz, collector current I C measured by a Rogowski coil CWT Mini50HF with a bandwidth of 50MHz. An MSO54 oscilloscope with a bandwidth of 1GHz is selected to capture and record the waveforms.

[0046] The two short circuit conditions of hard-on short circuit and load short circuit are verified respectively.

[0047] For the hard-on short circuit condition. As shown in Figure 6 the measurement result of the hard-on short circuit after using the conventional desaturation protection is shown. As shown in Figure 7 the measurement result of the hard-on short circuit after using the short circuit protection structure of the application is shown. When the upper tube driving waveform instantaneously increases, it indicates that a short circuit fault occurs.

[0048] Figure 6 In the middle, the short circuit signal DESAT jumps from low to high, indicating that a short circuit fault is recognized and shutdown protection is started, the protection delay is 1.56us, the shutdown current is as high as 1000A, and the shutdown voltage overshoot is as high as 320V.

[0049] And in Figure 7 , SC jumps from low to high, indicating that a short circuit fault is recognized, and SD jumps from low to high, indicating that the protection structure executes the device shutdown protection. From the actual occurrence of the short circuit fault to the detection of the short circuit fault, the delay is only 400ns, the short circuit protection speed is increased by 75%, and after recognizing the short circuit fault, the shutdown can be immediately executed. The shutdown current is only 132A, which is reduced by 85% compared with the desaturation short circuit current of 1000A; the shutdown voltage overshoot is only 220V, which is reduced by 32% compared with the desaturation protection shutdown voltage overshoot of 320V. Therefore, the present scheme can realize effective protection for hard-on short circuit.

[0050] For the load short circuit condition. As shown in Figure 8 the measurement result of the load short circuit after using the conventional desaturation protection is shown. As shown in Figure 9 the measurement result of the load short circuit after using the short circuit protection structure of the application is shown. When the upper tube driving waveform instantaneously increases, it indicates that a short circuit fault occurs.

[0051] Figure 8 In the middle, the short circuit signal DESAT jumps from low to high, indicating that a short circuit fault is recognized and shutdown protection is started, the protection delay is 240ns, the shutdown current is as high as 700A, and the shutdown voltage overshoot is as high as 480V.

[0052] And inFigure 9 In the circuit diagram, the transition of SC from low to high indicates the detection of a short-circuit fault, while the transition of SD from low to high indicates that the protection structure has initiated device shutdown protection. The delay from the actual occurrence of a short-circuit fault to its detection is only 160ns, compared to the 240ns delay of desaturation protection, representing a 34% improvement in short-circuit protection speed. Furthermore, after detecting a short-circuit fault, shutdown is not performed immediately; instead, it waits until the internal carrier concentration of the device is low and the device characteristics are relatively stable before executing shutdown. The shutdown current is only 550A, compared to 700A for desaturation short-circuit current, a 22% reduction. The shutdown voltage overshoot is only 420V, compared to 480V for desaturation protection, a 13% reduction in short-circuit shutdown voltage overshoot. Therefore, this solution can effectively protect the load from short circuits.

[0053] The experimental results show that the low turn-off overshoot short-circuit protection structure proposed in this invention can effectively improve the short-circuit detection speed, and by selecting a suitable turn-off tube break point, it can effectively reduce short-circuit turn-off overshoot, which is advanced.

[0054] In summary, this invention proposes a dual protection system for short-circuit failure of power switching devices, combining rapid identification and turn-off point control. Firstly, by integrating gate parameters and power-side parameters, it achieves online differentiation between hard-switching short circuits and normal turn-on, reducing the detection blanking time from the traditional 1.5-2 times the turn-on time to less than 1 time, significantly suppressing short-circuit current and reducing voltage overshoot under hard-switching short circuits. Secondly, it introduces device voltage criteria to optimize the load short-circuit turn-off point, triggering soft turn-off only after the voltage rises to a certain level, ensuring sufficient carrier evacuation and reducing turn-off overshoot. This short-circuit protection measure effectively reduces voltage overshoot under short circuits, minimizing the impact on power switching devices after a short circuit, and improving device voltage utilization and device lifespan.

[0055] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. It should be noted that the terms "in one embodiment," "for example," and "again" in this invention are intended to illustrate the invention and are not intended to limit the invention.

[0056] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A short-circuit protection structure for a switching power device that achieves low turn-off overshoot, comprising: The device comprises a detection module, a control module and a gate drive module, wherein, The detection module comprises a gate resistance voltage detection circuit, a conduction voltage drop detection circuit and a device voltage detection circuit; the gate resistance voltage detection circuit is used for detecting the gate resistance voltage of the device and outputting a detection voltage V G When the device enters a fully on state, V G <V ref1 , otherwise, V G ≥V ref1 , V ref1 is a reference voltage for judging the fully on state of the device; the conduction voltage drop detection circuit is used for detecting the conduction voltage drop of the device when the device is on and outputting a detection voltage V D When the device enters a fully on state, V D is equal to the conduction voltage drop, otherwise, V D is a ground voltage; the device voltage detection circuit is used for detecting the device voltage and outputting a detection voltage V H , and the voltage V H is proportional to the device voltage; The control module includes a short-circuit detection circuit and a shutdown detection circuit. The short-circuit detection circuit is used to determine the voltage V. G and voltage V D Determine if a short circuit fault has occurred and output a control signal S. SC When V G <V ref1 And V D ≥V ref2 At that time, V ref2 To determine the reference voltage at which a device desaturates, a short-circuit fault is identified; the shutdown determination circuit is used to determine the short-circuit fault based on signal S. SC and voltage V H Determine whether the device needs to be turned off and output control signal S. SD When signal S SC Indicates a short circuit fault and V H ≥V ref3 When it is determined that a short-circuit shutdown can be performed, V ref3 This is the threshold for the device to shut down during short-circuit operation. The gate drive module is configured to control the gate drive voltage of the device in accordance with a signal S SC and S SD determines the state of the device and controls the device drive voltage, when the device has not failed, the device drive voltage is controlled only by a normal drive signal of the device, when the device has a short circuit failure but does not need to be turned off, the device drive voltage is reduced, and when the device has a short circuit failure and needs to be turned off, the device is turned off.

2. The short protection structure of claim 1, wherein The gate resistance voltage detection circuit comprises differential amplifier circuit OP1 and diodes D1 and D2; The two inputs of the differential amplifier circuit OP1 are connected one-to-one via diodes D1, D2 to the terminals of the device gate resistor L g The output of the differential amplifier circuit OP1 outputs a detection voltage V G The detection voltage V G is equal to the voltage of the device gate resistor.

3. The short protection structure of claim 1, wherein The conduction voltage drop detection circuit comprises diode D3, current-limiting resistor R1, switch tube S1 and gate driver GD3; The cathode of diode D3 is connected to the collector C of the device, the anode is connected to the drain of switch tube S1 and one end of current-limiting resistor R1 respectively, the source of switch tube S1 is grounded, and the other end of current-limiting resistor R1 is used for connecting driving power source V CC , the gate driver GD3 is used for connecting normal driving signal PWM of the device, performing inversion operation, and then inputting to the gate of switch tube S1, and the drain of switch tube S1 outputs detection voltage V D .

4. The short protection structure of claim 1, wherein The device voltage detection circuit comprises voltage dividing resistors R2 and R3 and voltage dividing capacitors C1 and C2; One end of the resistor R2 is connected to the collector C of the device, the other end is grounded through the resistor R3, the capacitor C1 is connected in parallel with R2, the capacitor C2 is connected in parallel with R3, and the common end of the resistors R2 and R3 outputs a detection voltage V H .

5. The short protection structure of claim 1, wherein, The short circuit determination circuit comprises comparators CP1 and CP2 and AND gate operator IC1; The inverting input of the comparator CP1 is connected to the voltage V G , the non-inverting input is connected to the reference voltage V ref1 , and the output outputs a comparison level signal S G . The non-inverting input of the comparator CP2 is connected to the voltage V D , the inverting input is connected to the reference voltage V ref2 , and the output outputs a comparison level signal S D . AND gate operator IC1 is used for the access signal S G and signal S D AND gate operation is performed, and the control signal S SC is outputted. SC When the control signal S SC is high, it is determined that a short circuit failure has occurred. When the control signal S SC is low, it is determined that a short circuit failure has not occurred.

6. The short protection structure of claim 1, wherein, The turn-off determination circuit comprises comparator CP3, AND gate operator IC2 and latch IC3; The non-inverting input of the comparator CP3 is connected to the voltage V H The inverting input is used to connect to the reference voltage V ref3 The output outputs a comparison level signal S H ; The latch IC3 is used to latch the control signal S SC ; the control signal S SC is high, it is determined that a short-circuit fault occurs; the control signal S SC is low, it is determined that no short-circuit fault occurs; AND gate operator IC3 for input signal S H and the signal S latched by the latch IC3 SC and performs AND gate operation, outputting a control signal S SD ; the control signal S SC is high, it is determined that the device needs to be turned off, and the control signal S SC is low, it is determined that the device does not need to be turned off.

7. The short protection structure of claim 1, wherein The gate drive module comprises gate drive chips GD1 and GD2, NAND gate operator IC4 and OR gate operator IC5; The NAND gate operator IC4 is used to operate the inverted signal of the normal driving signal PWM of the device and the control signal S SC The input after the NAND operation is input to the input terminal of the gate driving chip GD1, and the output terminal of the gate driving chip GD1 is connected to the gate of the device; the control signal S SC When the control signal S is high, it is determined that a short circuit fault occurs SC When the control signal S is low, it is determined that no short circuit fault occurs; The OR gate operator IC4 is used to input the inverting signal of the device normal driving signal PWM and the control signal S SD The output of the OR gate operator IC4 is input to the input terminal of the gate driving chip GD2, and the output terminal of the gate driving chip GD2 is connected to the collector of the device. SC When the control signal S is high, it is determined that the device needs to be turned off. SC When the control signal S is low, it is determined that the device does not need to be turned off. A device driving voltage V is formed between the output terminal of the gate driving chip GD1 and the output terminal of GD2 DRV applied to the device; When the device does not have a short circuit fault, S SC is low, S SD is low, V DRV follows the normal driving signal PWM; when the device has a short circuit fault but does not need to be turned off, S SC is high, S SD is low, V DRV follows the normal driving signal PWM and the voltage value is pulled low compared to when there is no short circuit fault; when the device has a short circuit fault and needs to be turned off, S SC is high, S SD is high, the device driving voltage V DRV is pulled low to the device turn-off threshold.

8. The short protection structure of claim 1, wherein, Reference voltage V ref3 Set to where V BUS is the bus voltage, k is the proportionality factor of the voltage V H of the device.

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