Overcurrent Protection Circuit for IGBT Dynamic Testing and IGBT Dynamic Testing System

Abstract

One or more embodiments of the present invention provide an overcurrent protection circuit for IGBT dynamic testing and an IGBT dynamic testing system. The overcurrent protection circuit includes: a protection switch and a control circuit; the control circuit is connected to the first end, the second end, and the third end of the protection switch. The second end of the protection switch is connected to a power supply circuit, and the third end is connected to an IGBT dynamic testing loop. When the IGBT under test in the IGBT dynamic testing loop fails and shorts, the control circuit detects a first voltage between the second end and the third end of the protection switch, and turns off the protection switch when the first voltage exceeds a preset reference voltage, cutting off the direct discharge channel of the power supply circuit. The present invention can effectively limit the loop current when an overcurrent due to failure occurs in the IGBT dynamic testing system, protect the entire system from being impacted by a large current, has a simple circuit structure, and is fast and reliable.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic device testing, and particularly relates to an overcurrent protection circuit for IGBT dynamic testing and an IGBT dynamic testing system. Background Art

[0002] In an Insulated Gate Bipolar Transistor (IGBT) dynamic testing system, there is usually a large-capacity support capacitor for energy storage. When the IGBT under test fails, it will cause the capacitor to discharge directly, and the energy of the large-capacity capacitor will be instantaneously released through the test circuit, which will cause a great impact on the entire test system. If the protection is improper, it will accelerate the aging process of the equipment, increase the failure rate of the equipment, and seriously paralyze the entire test system. Therefore, it is extremely important to detect the overcurrent in the circuit within a short time and turn off the large current in a timely manner. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an overcurrent protection circuit for IGBT dynamic testing and an IGBT dynamic testing system to solve the problem of the great impact on the entire test system caused by the failure overcurrent in the IGBT dynamic testing system.

[0004] Based on the above object, one or more embodiments of the present invention provide an overcurrent protection circuit for IGBT dynamic testing, including: a protection switch and a control circuit; the control circuit is connected to the first end, the second end, and the third end of the protection switch, the second end of the protection switch is connected to a power supply circuit, and the third end is connected to an IGBT dynamic testing circuit; when the IGBT under test in the IGBT dynamic testing circuit fails and is short-circuited, the control circuit detects a first voltage between the second end and the third end of the protection switch, and turns off the protection switch when the first voltage exceeds a preset reference voltage, cutting off the direct discharge channel of the power supply circuit.

[0005] Optionally, the control circuit includes: a first diode, a first capacitor, a detection and drive circuit, and a microcontroller. The microcontroller is communicatively connected to the detection and drive circuit to transmit a fault signal and a control signal; the first end of the detection and drive circuit is connected to the anode of the first diode and is connected to the reference ground through the first capacitor. The cathode of the first diode is connected to the second end of the protection switch. The second end of the detection and drive circuit is connected to the third end of the protection switch and is connected to the reference ground. The third end of the detection and drive circuit is connected to the first end of the protection switch.

[0006] Optionally, the detection and drive circuit includes: a current source, a switching transistor, and a comparator; a first end of the detection and drive circuit is internally connected to the non-inverting input terminal of the comparator and the drain of the switching transistor, the first end of the detection and drive circuit is also connected to the current source internally, the inverting input terminal of the comparator is connected to the preset reference voltage, a second end of the detection and drive circuit is internally connected to the source of the switching transistor, and the gate of the switching transistor and the output terminal of the comparator are connected to the microcontroller.

[0007] Optionally, the control circuit further includes a first resistor, and the anode of the first diode is connected to the first end of the detection and drive circuit through the first resistor.

[0008] Optionally, the control circuit further includes: a second resistor, and a third end of the detection and drive circuit is connected to a first end of the protection switch through the second resistor.

[0009] Optionally, the protection switch is an IGBT transistor.

[0010] Optionally, the protection switch is a MOSFET transistor, and the overcurrent protection circuit further includes a second diode, the anode of the second diode is connected to a third end of the MOSFET transistor, and the cathode of the second diode is connected to a second end of the MOSFET transistor.

[0011] Optionally, a first end of the protection switch is a gate, a second end of the protection switch is a collector, and a third end of the protection switch is an emitter.

[0012] Based on the same inventive concept, one or more embodiments of the present invention further provide an IGBT dynamic test system, including: a power supply circuit, an IGBT dynamic test loop, and the aforementioned overcurrent protection circuit.

[0013] Optionally, the power supply circuit includes: a power supply, a first switch, and a support capacitor, a positive electrode of the power supply is connected to one end of the first switch, the other end of the first switch is connected to the overcurrent protection circuit and one end of the support capacitor, and a negative electrode of the power supply is connected to the other end of the support capacitor and the IGBT dynamic test loop.

[0014] As can be seen from the above, an overcurrent protection circuit for IGBT dynamic testing and an IGBT dynamic testing system provided by one or more embodiments of the present invention, the overcurrent protection circuit includes: a protection switch and a control circuit; the control circuit is connected to the first end, the second end and the third end of the protection switch, the second end of the protection switch is connected to the power supply circuit, and the third end is connected to the IGBT dynamic testing loop; when the IGBT under test in the IGBT dynamic testing loop fails and shorts, the control circuit detects a first voltage between the second end and the third end of the protection switch, and turns off the protection switch when the first voltage exceeds a preset reference voltage, cutting off the direct discharge channel of the power supply circuit, which can effectively limit the loop current when an overcurrent due to failure occurs in the IGBT dynamic testing system, protect the entire system from being impacted by large currents, the circuit structure is simple, and it is fast and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in one or more embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only one or more embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0016] Figure 1 FIG. is a schematic structural diagram of an overcurrent protection circuit for IGBT dynamic testing in one or more embodiments of the present invention;

[0017] Figure 2 FIG. is a circuit schematic diagram of the overcurrent protection circuit in one or more embodiments of the present invention;

[0018] Figure 3 FIG. is a schematic diagram of the working process of the protection switch in the overcurrent protection circuit in one or more embodiments of the present invention;

[0019] Figure 4 FIG. is a circuit schematic diagram of another overcurrent protection circuit in one or more embodiments of the present invention;

[0020] Figure 5 FIG. is a schematic diagram of the IGBT output curve in one or more embodiments of the present invention;

[0021] Figure 6 FIG. is a circuit schematic diagram of yet another overcurrent protection circuit in one or more embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the following further describes the present disclosure in detail with reference to specific embodiments and the accompanying drawings.

[0023] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in one or more embodiments of the present invention should have the ordinary meanings understood by those of ordinary skill in the art to which this disclosure pertains. The terms "first", "second" and similar terms used in one or more embodiments of the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. Words such as "comprising" or "including" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Upper", "lower", "left", "right", etc. are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0024] One or more embodiments of the present invention provide an overcurrent protection circuit for IGBT dynamic testing. As shown in the appendix Figure 1 As shown, the overcurrent protection circuit 10 includes: a protection switch VT1 and a control circuit 101; the control circuit 101 is connected to the first end, the second end and the third end of the protection switch VT1, the second end of the protection switch VT1 is connected to the power supply circuit 30, and the third end is connected to the IGBT dynamic test circuit 20; when the IGBT under test in the IGBT dynamic test circuit 20 fails and shorts, the control circuit 101 detects the first voltage Vce between the second end and the third end of the protection switch VT1, and turns off the protection switch VT1 when the first voltage Vce exceeds the preset reference voltage Vceset, cutting off the direct discharge channel of the power supply circuit 30. The first end of the protection switch VT1 is the gate, the second end of the protection switch VT1 is the collector, and the third end of the protection switch VT1 is the emitter.

[0025] In an embodiment of the present invention, as shown in Figure 2 As shown, the control circuit 101 includes a first diode VD1, a first capacitor Cb1, a detection and drive circuit 102 and a microcontroller 103. The microcontroller 103 is communicatively connected to the detection and drive circuit 102 to transmit fault signals and control signals; the first end of the detection and drive circuit 102 is connected to the anode of the first diode VD1 and is connected to the reference ground through the first capacitor Cb1, the cathode of the first diode VD1 is connected to the second end of the protection switch VT1, the second end of the detection and drive circuit 102 is connected to the third end of the protection switch VT1 and is connected to the reference ground GND, and the third end of the detection and drive circuit 102 is connected to the first end of the protection switch VT1.

[0026] Optionally, the control circuit 101 further includes a first resistor R1 and a second resistor R2. The anode of the first diode VD1 is connected to the first end of the detection driving circuit 102 through the first resistor R1, and the third end Uout of the detection driving circuit 102 is connected to the first end of the protection switch VT1 through the second resistor R2.

[0027] In the embodiment of the present invention, the protection switch may be an IGBT transistor. As a power electronic device, when the output current of an IGBT exceeds a certain value (generally 4 to 6 times), the IGBT device will enter the desaturation state and the output current will no longer increase. At the same time, IGBT devices of different levels can turn off tens of thousands of amperes of current, and the turn-off time is only a few microseconds, with a fast and reliable response speed. Connecting a protection IGBT device with a greater current output capacity in series into the IGBT dynamic test system, when a through-fault occurs in the loop, the protection IGBT device will enter the desaturation state in about 2 to 3 microseconds, and limit the loop current from rising within this time. At this time, the control circuit can quickly detect the desaturation and turn off the circuit, which is of great significance for the protection of the IGBT dynamic test system.

[0028] The following takes the protection switch being an IGBT transistor as an example to illustrate Figure 2 the working principle of the overcurrent protection circuit in: When the IGBT dynamic test loop 20 is working normally, the first diode VD1 is conducting and the protection switch VT1 is conducting. When the measured IGBT VT2 in the IGBT dynamic test loop 20 fails and causes a short circuit in the IGBT dynamic test loop 20, combined with Figure 3 , the power supply circuit 30 will directly short-circuit and discharge through the protection switch VT1, and the loop current Ic will rise rapidly. According to the characteristics of the IGBT device, the IGBT will enter the desaturation state after the current rises to a certain amplitude. After the IGBT enters the desaturation state, the collector-emitter voltage Vce of the IGBT will rise. When Vce is greater than a certain amplitude, the detection driving circuit 102 will be activated, and the first capacitor Cbl will be charged through the detection driving circuit 102. When the voltage on the first capacitor Cbl is greater than the driving preset reference voltage Vceset, the microcontroller 103 will send a control signal (low-level turn-off signal) to the detection driving circuit 102, and output a low-level signal to the gate of the IGBT through the detection driving circuit 102 to control the IGBT to turn off, cutting off the through-discharge channel of the power supply circuit 30 and protecting the entire IGBT dynamic test system.

[0029] More specifically, as Figure 4As shown in the figure, the detection and drive circuit 102 includes: a current source Is, a switching transistor VT3, and a comparator U1. The first end of the detection and drive circuit 102 is internally connected to the non-inverting input terminal of the comparator U1 and the drain of the switching transistor VT3, and the first end of the detection and drive circuit 102 is also connected to the current source Is internally. The inverting input terminal of the comparator U1 is connected to a preset reference voltage Uceset. The second end of the detection and drive circuit 102 is internally connected to the source of the switching transistor VT3. The gate of the switching transistor VT3 and the output terminal of the comparator U1 can be directly connected to the microcontroller 103, and the output terminal of the comparator U1 directly transmits a fault signal to the microcontroller 103. The switching transistor VT3 is preferably a PMOS transistor. When the IGBT dynamic test loop 20 operates normally, the first diode VD1 conducts, the protection switch VT1 conducts, and the current of the current source Is flows along the first resistor R1 and the first diode VD1 to the protection switch VT1. When the measured IGBT VT2 in the IGBT dynamic test loop 20 fails and causes the IGBT dynamic test loop 20 to short-circuit, and after the IGBT enters the desaturation state, the collector-emitter voltage Vce of the IGBT will rise. After Vce is greater than a certain amplitude, the first diode VD1 turns off, and the current source Is inside the detection and drive circuit 102 starts to charge the first capacitor Cb1. When the voltage on the first capacitor Cbl is greater than the driving preset reference voltage Vceset, the microcontroller 103 will send a control signal (low-level turn-off signal) to the detection and drive circuit 102, and control the IGBT to turn off through the detection and drive circuit 102, cutting off the direct discharge channel of the power supply circuit 30 to protect the entire IGBT dynamic test system.

[0030] In the embodiment of the present invention, after the measured IGBT VT2 fails and overcurrents, the protection IGBT VT1 will enter the desaturation state to limit the loop current from rising further. Figure 5As can be seen from the IGBT output curve shown, the desaturation current of the IGBT is different under different gate voltage drive conditions. Under a gate voltage of 15V, it is generally 4 to 6 times the rated current. According to the IGBT characteristics, when the current through the protection IGBT VT1 reaches about 4 to 6 times the rated current under a 15V gate voltage drive, it will enter the desaturation state. At this time, due to the limitation of the desaturation current of the protection IGBT VT1, the current in the IGBT dynamic test circuit will not rise any further. Different current-level protection IGBT VT1s can be selected according to different application requirements, as well as different gate voltage drives, in order to limit the maximum current in the circuit. For example: For an IGBT with a rated current of 1500A, its desaturation current under a 15V gate voltage is 6000A. If the maximum test current of the test system is 5000A, then the IGBT can be selected. The drive gate voltage is set to 15V. When testing normally, the circuit current will be less than 5000A, and the protection IGBT will operate in the linear region without affecting the test circuit. When the IGBT VT2 under test in the test system fails, the circuit current will quickly rise to 6000A, and the protection IGBT will quickly desaturate. The circuit current will be limited to 6000A and will not rise any further. At the same time, the Vce voltage drop of the protection IGBT will quickly rise and be greater than the drive preset reference voltage Vceset. The microcontroller will send a turn-off signal to turn off the protection IGBT, and the discharge circuit will be cut off. If the maximum test current of the circuit is only 3000A, and the desaturation current of this protection IGBT under a 14V gate voltage is 4000A, then the drive voltage can be set at 14V, and the working process is the same as above. If the maximum test current of the circuit is 10000A, then a protection IGBT with a larger current level can be selected, such as a protection IGBT with a rated current of 2400A.

[0031] In the embodiment of the present invention, as Figure 6 shown, the protection switch can also be the MOSFET transistor VT4. At this time, the overcurrent protection circuit 10 further includes a second diode VD2. The anode of the second diode VD2 is connected to the third terminal of the MOSFET transistor VT4, and the cathode of the second diode VD2 is connected to the second terminal of the MOSFET transistor VT4. This power MOSFET device has similar characteristics to the IGBT, and the specific working principle is the same as that of the IGBT, which will not be elaborated here.

[0032] In the embodiment of the present invention, by utilizing the characteristic that the IGBT device enters the desaturation state and the current no longer rises after the current reaches a certain multiple, when an overcurrent fault occurs in the loop, the protection IGBT will limit the current in the loop from rising. At the same time, by using the characteristic that the collector-emitter voltage Vce of the IGBT device rises after current desaturation, after the drive circuit detects that Vce is greater than a preset value Vceset, the device will be turned off within a few microseconds, cutting off the loop between the power supply circuit and the IGBT dynamic test loop, protecting the entire test system from being impacted by large currents, protecting the device failure site for easy analysis of the failure cause, and at the same time avoiding damage to the test system caused by current impact. The embodiment of the present invention does not require an additional overcurrent detection system. The protection IGBT can play a dual role of limiting the loop current and detecting overcurrent, with a simple circuit structure, and being fast and reliable. The overcurrent protection circuit for IGBT dynamic testing in the embodiment of the present invention is applicable to current loops from several amperes to tens of thousands of amperes. The normal operating current and the overcurrent protection value can be controlled by using IGBTs with different current ratings and different gate voltages for driving, and different voltage and current level test systems can be adapted by connecting different numbers of protection IGBTs in parallel or in series.

[0033] The overcurrent protection circuit for IGBT dynamic testing in the embodiment of the present invention includes: a protection switch and a control circuit; the control circuit is connected to the first end, the second end, and the third end of the protection switch. The second end of the protection switch is connected to the power supply circuit, and the third end is connected to the IGBT dynamic test loop; when the DUT IGBT in the IGBT dynamic test loop fails and shorts, the control circuit detects a first voltage between the second end and the third end of the protection switch, and turns off the protection switch when the first voltage exceeds a preset reference voltage, cutting off the direct discharge channel of the power supply circuit, which can effectively limit the loop current when an overcurrent occurs in the IGBT dynamic test system, protecting the entire system from being impacted by large currents, with a simple circuit structure, and being fast and reliable.

[0034] Based on the same inventive concept, one or more embodiments of the present invention also provide an IGBT dynamic test system. Please continue to refer to Figure 2, the IGBT dynamic test system includes a power supply circuit 30, an IGBT dynamic test loop 20, and the aforementioned overcurrent protection circuit 10. The overcurrent protection circuit 10 is connected in series between the power supply circuit 30 and the IGBT dynamic test loop 20. The power supply circuit 30 includes: a power supply Vs, a first switch K, and a support capacitor C1. The positive electrode of the power supply Vs is connected to one end of the first switch K. The other end of the first switch K is connected to the overcurrent protection circuit 10 and one end of the support capacitor C1. The negative electrode of the power supply Vs is connected to the other end of the support capacitor C1 and the IGBT dynamic test loop 20. For the specific circuit structure of the overcurrent protection circuit 10, refer to the previous introduction and will not be elaborated here. After the IGBT dynamic test loop 20 fails and shorts, the support capacitor C1 will instantaneously discharge through the failed IGBT dynamic test loop 20. The overcurrent protection circuit 10 will timely turn off the discharge path of the support capacitor C1 to avoid direct capacitor discharge, thereby protecting the entire IGBT dynamic test system.

[0035] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present disclosure (including the claims) is limited to these examples; under the concept of the present disclosure, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of one or more embodiments of the present application as described above, and they are not provided in detail for the sake of brevity.

[0036] One or more embodiments of the present application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present application shall be included within the protection scope of the present disclosure.

Claims

1. An overcurrent protection circuit for IGBT dynamic testing, characterized in that, the overcurrent protection circuit includes: a protection switch and a control circuit; the control circuit is connected to the first end, the second end and the third end of the protection switch, the second end of the protection switch is connected to the power supply circuit, and the third end is connected to the IGBT dynamic test loop; the control circuit includes: a first diode, a first capacitor, a detection and drive circuit, and a microcontroller. The microcontroller is communicatively connected to the detection and drive circuit to transmit fault signals and control signals; the first end of the detection and drive circuit is connected to the anode of the first diode and is grounded through the first capacitor. The cathode of the first diode is connected to the second end of the protection switch. The second end of the detection and drive circuit is connected to the third end of the protection switch and is grounded. The third end of the detection and drive circuit is connected to the first end of the protection switch; the protection switch is an IGBT transistor, or the protection switch is a MOSFET transistor, and the overcurrent protection circuit further includes a second diode. The anode of the second diode is connected to the third end of the MOSFET transistor, and the cathode of the second diode is connected to the second end of the MOSFET transistor; the detection and drive circuit includes: a current source, a switching transistor, and a comparator; the first end of the detection and drive circuit is internally connected to the non-inverting input terminal of the comparator and the drain of the switching transistor. The first end of the detection and drive circuit is also internally connected to the current source. The inverting input terminal of the comparator is connected to a preset reference voltage. The second end of the detection and drive circuit is internally connected to the source of the switching transistor. The gate of the switching transistor and the output terminal of the comparator are connected to the microcontroller; when the DUT IGBT in the IGBT dynamic test loop fails and shorts, the detection and drive circuit charges the first capacitor. When the voltage on the first capacitor is greater than the preset reference voltage, the microcontroller will send a control signal to the detection and drive circuit, and the detection and drive circuit outputs a low-level signal to the gate of the IGBT to control the IGBT to turn off and cut off the direct discharge path of the power supply circuit.

2. The overcurrent protection circuit according to claim 1, characterized in that, the control circuit further includes a first resistor, and the anode of the first diode is connected to the first end of the detection and drive circuit through the first resistor.

3. The overcurrent protection circuit according to claim 1, characterized in that, the control circuit further includes: a second resistor, and the third end of the detection and drive circuit is connected to the first end of the protection switch through the second resistor.

4. The overcurrent protection circuit according to any one of claims 1-3, characterized in that, the first end of the protection switch is the gate, the second end of the protection switch is the collector, and the third end of the protection switch is the emitter.

5. An IGBT dynamic test system, characterized in that, the IGBT dynamic test system includes: a power supply circuit, an IGBT dynamic test loop, and the overcurrent protection circuit according to any one of claims 1-4.

6. The IGBT dynamic test system according to claim 5, characterized in that, the power supply circuit includes: a power supply, a first switch, and a support capacitor. The positive electrode of the power supply is connected to one end of the first switch, the other end of the first switch is connected to the overcurrent protection circuit and one end of the support capacitor, and the negative electrode of the power supply is connected to the other end of the support capacitor and the IGBT dynamic test loop.

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