Short-circuit protection structure for switching power devices with low turn-off overshoot

Abstract

This invention belongs to the technical field of short-circuit protection for power electronic equipment. It discloses a short-circuit protection structure for switching power devices with low turn-off overshoot, wherein a gate resistor voltage detection circuit detects the gate resistor voltage of the device and outputs a detection voltage V. G The on-state voltage drop detection circuit detects the on-state voltage drop when the device is turned on and outputs a detection voltage V. D The device voltage detection circuit detects the device voltage and outputs the detected voltage V. H The short-circuit detection circuit is based on the voltage V. G and V D Determine if a short circuit fault has occurred and output a control signal S. SC The shutdown determination circuit is based on S SC and V H Determine whether the device needs to be turned off and output control signal S. SD The gate drive module is used to determine the gate drive module based on S. SC and S SD The device status is determined and the device drive voltage is controlled. Through the above short-circuit protection structure, the response speed to short-circuit faults can be improved and appropriate timing shut-off devices can be selected, thereby effectively reducing short-circuit overshoot.

Description

Technical Field

[0001] This invention belongs to the technical field of short-circuit protection for power electronic equipment, and more specifically, relates to a short-circuit protection structure for switching power devices that achieves low turn-off overshoot. Background Technology

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

[0003] Given a fixed rated capacity for power switching devices, engineering applications urgently need to improve device voltage utilization while meeting insulation and thermal design boundaries. However, practice shows that turn-off voltage overshoot under short-circuit conditions is the main factor limiting the improvement of power switching device voltage utilization. Current datasheets typically recommend that the actual operating voltage be approximately 75% of the rated value, resulting in excessive design redundancy and difficulty in further reducing size and cost. Short-circuit protection within the driver board is the primary protection mechanism after a short circuit occurs, and its detection scheme and turn-off strategy directly affect the peak short-circuit current and turn-off overvoltage. However, current short-circuit protection mechanisms generally suffer from problems such as delayed short-circuit fault detection and unreasonable turn-off timing selection, leading to significant short-circuit overshoot phenomena.

[0004] Therefore, improving the response speed of short-circuit faults and selecting appropriate timing interruption devices to effectively reduce short-circuit overshoot are technical problems that urgently need to be solved. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides a short-circuit protection structure for switching power devices with low turn-off overshoot. Its purpose is to improve the response speed of short-circuit faults and select appropriate time-shutdown devices, thereby effectively reducing short-circuit overshoot.

[0006] To achieve the above objectives, a short-circuit protection structure for switching power devices with low turn-off overshoot is proposed, comprising a detection module, a control module, and a gate drive module, wherein...

[0007] The detection module includes a gate resistance voltage detection circuit, a forward voltage drop detection circuit, and a device voltage detection circuit; the gate resistance voltage detection circuit is used to detect the gate resistance voltage of the device and output a detection voltage V. G When the device enters the fully on state, V G <V ref1 Otherwise, V G ≥V ref1 V ref1The reference voltage for determining the fully conduction state of the device; the conduction voltage drop detection circuit is used to detect the conduction voltage drop when the device is conducting and output a detection voltage V. D When the device enters the fully on state, V D Equal to the on-state voltage drop, otherwise, V D The voltage is grounded; the device voltage detection circuit is used to detect the device voltage and output the detection voltage V. H Voltage V H It is proportional to the device voltage;

[0008] 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 At that time, V ref3 The upper limit of the safe operating voltage of the device determines whether the device needs to be turned off.

[0009] The gate driving module is used to determine 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.

[0010] In summary, compared with the prior art, the technical solutions conceived in this invention have the following main advantages:

[0011] This invention acquires the gate resistor voltage through a gate resistor voltage detection circuit. Based on changes in the gate resistor voltage, it identifies whether the device has entered a fully conducting state. It also acquires the device's on-state voltage drop through a on-state voltage drop detection circuit. Based on changes in the on-state voltage drop, it identifies whether the device has experienced desaturation. Combining the detection results from both circuits, a short-circuit fault is determined. If desaturation occurs even when the device is fully conducting, a short-circuit fault has occurred. This allows for accurate and rapid identification of short-circuit faults, avoiding misjudgments. Furthermore, this invention also acquires the device voltage through a device voltage detection circuit. Combining the detection results from both circuits with the short-circuit determination circuit, a short-circuit turn-off point is determined. When a short-circuit fault occurs and the device voltage rises close to the device's operating voltage, it indicates a low carrier concentration, relatively stable device characteristics, controllable turn-off current rate, and minimal turn-off overshoot. Overall, based on the short-circuit protection structure for switching power devices mentioned in this invention, the response speed to short-circuit faults can be improved, and appropriate timing for turning off devices can be selected, thereby effectively reducing short-circuit overshoot. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a short-circuit protection structure for a switching power device according to an embodiment of the present invention.

[0013] Figure 2 This is a schematic diagram of the structure of a power switching device according to an embodiment of the present invention.

[0014] Figure 3 This is a circuit diagram of the detection module in one embodiment of the present invention.

[0015] Figure 4 This is a circuit diagram of the control module in one embodiment of the present invention.

[0016] Figure 5 This is a circuit diagram of the gate driving module in one embodiment of the present invention.

[0017] Figure 6 The results are from a hard-open short-circuit measurement after applying conventional desaturation protection.

[0018] Figure 7 The results are from a hard-open short-circuit measurement after protection using the short-circuit protection structure of this invention.

[0019] Figure 8 The results are from load short-circuit measurements after applying conventional desaturation protection.

[0020] Figure 9 The results are the load short-circuit measurement results after protection using the short-circuit protection structure of this invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0022] In a first aspect, the present invention claims a short-circuit protection structure for a switching power device that achieves low turn-off overshoot.

[0023] like Figure 1 The diagram shown is a schematic representation of a short-circuit protection structure for a switching power device according to an embodiment of the present invention. Figure 2 The diagram shown is a schematic of the power switching device in one embodiment. Taking an IGBT as an example, its gate is connected to a gate resistor R. g The device drive voltage is applied through the gate resistor R. g Applied to power switching devices.

[0024] This short-circuit protection structure for a switching power device includes a detection module, a control module, and a gate drive module. The detection module includes a gate 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.

[0025] The gate resistance voltage detection circuit is used to detect the gate resistance voltage of the device and output the detection voltage V. G When the device enters the fully on state, V G <V ref1 Otherwise, V G ≥V ref1 V ref1 This serves as a reference voltage for determining the fully on state of a device. For power switching devices, a reference voltage V can be set to determine the fully on state of the device. ref1 By collecting the gate resistance voltage, the device can identify whether it has entered a fully conductive state based on the change in the gate resistance voltage.

[0026] The on-state voltage drop detection circuit is used to detect the on-state voltage drop when a device is turned on and outputs a detection voltage V. D When the device enters the fully on state, V D Equal to the on-state voltage drop, otherwise, V D This is the ground voltage. For power switching devices, if a short-circuit fault occurs, the device will experience desaturation, and its on-state voltage drop will increase sharply. Therefore, a reference voltage V can be set to determine if the device has experienced desaturation. ref2 By collecting the on-state voltage drop, the device can identify whether desaturation has occurred based on the changes in the on-state voltage drop.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] like Figure 3 The diagram shown is a circuit diagram of the detection module in one embodiment of the present invention.

[0032] In one embodiment, the gate resistor voltage detection circuit 11 includes a differential amplifier circuit OP1 and diodes D1 and D2. The two input terminals of the differential amplifier circuit OP1 are connected one-to-one to the device gate resistor R through diodes D1 and D2. g At both ends, the gate resistor R g The two ends are represented as R g-1 and R g-2 The output of the differential amplifier circuit OP1 outputs the detection voltage V. G Detecting voltage V G It is equal to the voltage across the device's gate resistance.

[0033] In one embodiment, the on-state voltage drop detection circuit 12 includes: a diode D3, a current-limiting resistor R1, a switching transistor S1, and a gate driver GD3; the cathode of the diode D3 is connected to the collector C of the device, the anode is connected to the drain of the switching transistor S1 and one end of the current-limiting resistor R1, the source of the switching transistor S1 is grounded, and the other end of the current-limiting resistor R1 is used to connect to the driving power supply V. CC The gate driver GD3 is used to input the normal drive signal PWM of the device and, after inverting it, input it to the gate of the switching transistor S1. The drain output of the switching transistor S1 detects the voltage V. D .

[0034] In this embodiment, the gate driver GD3 has an inverted output function;

[0035] When the normal drive signal PWM of the device is high: power device S0 is turned on, GD3 outputs a low level to turn off S1. During this period when power device S0 is turned on and desaturation has not occurred, when the on-state voltage drop of S0 is less than V... CC When diode D3 is turned on, voltage V D The on-state voltage drop V equals S0 CE(sat) With the forward voltage drop V of diode D3 F When S0 is turned on and desaturation occurs, the voltage drop rises to a value greater than V. CC After that, D1 ends, and at this time V D Voltage equals V CC ;

[0036] When the normal drive signal PWM of the device is low: power device S0 is off, GD3 outputs a low level to turn on S1, D3 is cut off, and the withstand voltage V... D =0.

[0037] In one embodiment, the device voltage detection circuit 13 includes: voltage divider resistors R2 and R3 and voltage divider capacitors C1 and C2. Resistors R2 and R3 are connected in series, C1 and R2 are connected in parallel, and C2 and R3 are connected in parallel to form a voltage divider structure. The voltage divider ratio k = R3 / (R2+R3), and the output voltage V H The drain-source voltage V of the power device CE The relation satisfies: V H =k V CE .

[0038] like Figure 4 The diagram shown is a circuit diagram of the control module in one embodiment of the present invention.

[0039] In one embodiment, the short-circuit detection circuit includes comparators CP1 and CP2 and an AND gate IC1; the inverting input of comparator CP1 is connected to a voltage V. G The non-inverting input is used to connect the reference voltage V. ref1 The output terminal outputs a comparison level signal S. G The non-inverting input of comparator CP2 is connected to voltage V. D The inverting input is used to connect the reference voltage V. ref2 The output terminal outputs a comparison level signal S. D AND gate IC1 is used to input signal S G and signal S D It performs an AND gate operation and outputs a control signal S. SC .

[0040] In this embodiment, when power device S0 is turned off, the gate current is large, and its gate resistance voltage is large. When power device S0 is turned on, its gate resistance voltage is also large during the turn-on transient, and then the voltage drops to a lower value, entering a fully on state. Therefore, by setting the reference voltage V... ref1 The voltage V is compared using comparator CP1. G and V ref1 When V G <V ref1 When the power device S0 is determined to be fully on, comparator CP1 outputs a high level, and S... G =1, that is, S G =1 indicates that the power device is close to or has reached a fully turned-on state; otherwise, S G =0. In practical operation, the reference voltage V... ref1 It can be set to V DRV-ON V is the turn-on drive voltage connected to the gate resistor. mil S 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... GOutput high level.

[0041] In this embodiment, when the power device S0 is turned off, V D =0, when the power device S0 is turned on and desaturation has not occurred, the device's on-state voltage is a relatively small value, i.e., V. D The voltage is relatively small. When the power device S0 turns on and desaturation occurs, the device's on-state voltage increases instantaneously, i.e., V. D The value is relatively large. Therefore, by setting the reference voltage V... ref2 The voltage V is compared using comparator CP2. D and V ref2 When V D ≥V ref2 When power device S0 is desaturated, comparator CP2 outputs a high level. D =1, that is, S D =1 indicates that the current flowing through the power device is large, and desaturation has occurred; otherwise, S D =0. In practical operation, the reference voltage V ref2 It can be set to V sat For power devices at rated drive voltage and twice rated current I CM The saturation voltage value under [condition]. When the power device desaturates, S [value]. D Output high level.

[0042] In this embodiment, the signal S is processed by the AND gate arithmetic unit IC1. G and signal S D Perform an AND gate operation only if S G =1 and S D When =1, the AND gate IC1 outputs a high level, S SC =1, meaning that desaturation only occurs when the device is fully on, indicating a short circuit fault. It should be noted that desaturation occurs both during a short circuit fault and during the device's turn-on transient. If desaturation is used directly as the criterion for short circuit faults, the device's turn-on transient might also be mistaken for a short circuit fault, leading to misjudgment. In this invention, the judgment is made by combining the detection results of the gate resistor voltage detection circuit and the on-state voltage drop detection circuit. Desaturation occurring when the device is fully on indicates a short circuit fault, thus enabling accurate and rapid identification of short circuit faults and avoiding misjudgment.

[0043] In one embodiment, the shutdown determination circuit includes a comparator CP3, an AND gate arithmetic unit IC2, and a latch IC3; the non-inverting input of the comparator CP3 is connected to a voltage V. H The inverting input is used to connect the reference voltage V. ref3 The output terminal outputs a comparison level signal S.H Latch IC3 is used to control signal S SC Latching is performed; AND gate arithmetic unit IC3 is used to input signal S. H The signal S latched by latch IC3 SC It performs an AND gate operation and outputs a control signal S. SD .

[0044] In this embodiment, when a short-circuit fault occurs and the device voltage continues to rise to a certain value, the concentration of excess carriers inside the device is low. At this time, the rate of decrease of the short-circuit current when turning off the device is highly controllable, and the peak value of the turn-off voltage is low. Therefore, by setting a short-circuit turn-off point threshold V... ref3 The voltage V is compared using comparator CP3. H and V ref3 When V H <V ref3 When the voltage of power device S0 rises to a suitable short-circuit cutoff point, comparator CP1 outputs a low level, and S... H =0, that is, S H =0 indicates that the power device is not yet suitable for short-circuit shutdown. When V H ≥V ref3 When it is determined that the voltage of power device S0 has risen to the appropriate short-circuit cutoff point, comparator CP1 outputs a high level, and 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 practical operation, the reference voltage V... ref3 It can be set to , where V BUS This is the bus voltage.

[0045] In this embodiment, the signal S is processed by the AND gate arithmetic unit IC2. H and signal S SC Perform an AND gate operation only if S H =1 and S SC When =1, the AND gate IC2 outputs a high level, S SD=1, meaning that the device needs to be turned off only when a short-circuit fault occurs and the device voltage rises to a suitable short-circuit turn-off point. It should be noted that if the device is turned off directly upon the occurrence of a short-circuit fault, especially if the short-circuit fault is a load short-circuit fault, the device voltage will be low, and the internal carriers will not be fully emptied, potentially leading to turn-off overshoot. In this invention, the judgment is made by combining the detection results of the device voltage detection circuit and the judgment results of the short-circuit determination circuit. When a short-circuit fault occurs and the device voltage rises to a suitable short-circuit turn-off point, the internal carrier concentration of the device is low, the device characteristics are relatively stable, the turn-off current rate is controllable, the device can be turned off, and the turn-off overshoot is small.

[0046] like Figure 5 The diagram shown is a circuit diagram of a gate driving module according to an embodiment of the present invention.

[0047] In one embodiment, the gate driving module includes: gate driving chips GD1 and GD2, a NAND gate IC4, and an OR gate IC5; the NAND gate IC4 is used to invert the normal drive signal PWM and the control signal S. SC After performing a NAND operation, the signal is input to the gate driver chip GD1, and the output of the gate driver chip GD1 is connected to the gate of the device; the OR gate IC4 is used to invert the normal drive signal PWM and the control signal S. SD After performing an OR operation, the input is sent to the input terminal of the gate driver chip GD2, and the output terminal of the gate driver chip GD2 is connected to the emitter of the device; the device driving voltage V is formed between the output terminals of the gate driver chips GD1 and GD2. DRV .

[0048] In this embodiment, when the device does not experience a short-circuit fault, S SC S is low level. SD When the voltage is low, IC4 outputs a high level, and IC5 follows the inverted signal of the normal drive signal PWM. The device drive voltage V DRV Follows the normal drive signal PWM changes; when the device experiences a short-circuit fault but does not need to be turned off, S SC S is a high level. SD When the voltage is low, IC4 follows the normal drive signal PWM, and IC5 follows the inverted signal of the normal drive signal PWM. The device drive voltage V DRV The voltage is pulled low compared to when there is no short-circuit fault, following the normal drive signal PWM changes; when the device experiences a short-circuit fault and needs to be turned off, S... SC S is a high level. SD When the voltage is high, IC4 follows the normal drive signal PWM, IC5 outputs a high level, and the device drive voltage V... DRVIt was pulled down to the device shutdown threshold.

[0049] In specific settings, the GD1 input power is V. CC and V EE The input power supply for GD2 is GND and V. EE V EE The voltage level is negative. During normal driving, GD1 outputs a high level V. CC GD2 outputs a low level VEE, and the device drive voltage V... DRV =V CC -V EE When S SC After 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.

[0050] 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.

[0051] 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.

[0052] In the experiment, V D V H V G S D S H S G S SC S SD The signals at each signal point were measured by a TDDP1000 low-voltage differential probe with a bandwidth of 1 GHz, and the collector-emitter voltage V... CE Collector current I was measured by a THDP0200 with a bandwidth of 200MHz. C The waveform was measured using a Rogowski coil CWT Mini50HF with a bandwidth of 50MHz. An MSO54 oscilloscope with a bandwidth of 1GHz was selected to capture and record the waveform.

[0053] The two short circuit scenarios, hard-open short circuit and load short circuit, were verified separately.

[0054] For situations involving hard-open short circuits, such as... Figure 6 The image shows the measurement results of a hard-open short circuit after applying conventional desaturation protection. Figure 7 The image shows the hard-turn-on short-circuit measurement results after protection using the short-circuit protection structure of this invention. A sudden increase in the upper transistor drive waveform indicates a short-circuit fault has occurred.

[0055] Figure 6 In the short circuit signal DESAT, the transition from low to high level indicates that a short circuit fault has been detected and the shutdown protection has been activated. The protection delay is 1.56μs, the shutdown current is as high as 1000A, and the shutdown voltage overshoot is as high as 320V.

[0056] And in Figure 7In the circuit, the transition of SC from low to high indicates that a short-circuit fault has been detected, and the transition of SD from low to high indicates that the protection mechanism has shut down the protection device. The delay from the actual occurrence of a short-circuit fault to its detection is only 400ns, which improves the short-circuit protection speed by 75%. Moreover, after the short-circuit fault is detected, it can immediately shut down the fault with a shutdown current of only 132A, which is 85% lower than the 1000A short-circuit current of desaturation protection. The shutdown voltage overshoot is only 220V, which is 320V lower than the 320V shutdown voltage overshoot of desaturation protection. Therefore, this solution can effectively protect against hard-open short circuits.

[0057] For situations involving load short circuits, such as... Figure 8 The image shows the load short-circuit measurement results after applying conventional desaturation protection. Figure 9 The image shows the load short-circuit measurement results after protection using the short-circuit protection structure of this invention. A sudden increase in the upper transistor drive waveform indicates a short-circuit fault has occurred.

[0058] Figure 8 In the short circuit signal DESAT, the transition from low to high indicates that a short circuit fault has been detected and the shutdown protection has been activated. The protection delay is 240ns, the shutdown current is as high as 700A, and the shutdown voltage overshoot is as high as 480V.

[0059] And in Figure 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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 conducting state, V G <V ref1 , otherwise, V G ≥V ref1 , V ref1 is a reference voltage for judging the fully conducting 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 conducting and outputting a detection voltage V D When the device enters a fully conducting 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 of the switching power device 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 two terminals of the device gate resistor R 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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