Overcurrent protection circuit and power device testing device

Abstract

The utility model relates to the technical field of power electronics, and discloses an overcurrent protection circuit and a power device testing device, which comprise a current limiting circuit, a control circuit and an overcurrent detection circuit, the first output end and the second output end of the current-limiting circuit are correspondingly connected with the first end and the second end of the current-limiting circuit respectively; the third end and the fourth end of the current limiting circuit are respectively connected with the first input end and the second input end of the overcurrent detection circuit, and the third end and the fourth end of the current limiting circuit are respectively and correspondingly connected with the first end and the second end of a probe; and the output end of the over-current detection circuit is connected with an operating system, and when the voltage at the third end or the fourth end of the current limiting circuit rises, the over-current detection circuit is switched on and sends an over-current signal to the operating system. According to the utility model, bidirectional over-current protection can be carried out on the probe, the over-current in the probe can be reduced regardless of the direction of the over-current in the probe, and the probe is prevented from being burnt.

Description

Technical Field

[0001] The utility model relates to the technical field of power electronics, in particular to an overcurrent protection circuit and a power device testing device. Background Art

[0002] With the development of new energy vehicles, high-power switching devices are increasingly used. The use of high currents for testing these power devices during wafer testing is also increasing. Before packaging, these power switching devices need to undergo wafer testing (Chip Probing, CP), bare crystal testing, and known good die (KGD) testing. These tests generally use probes as a contact method, and the current load capacity of the probes is generally only a few amperes. In the case of testing large currents, multiple probes need to be connected in parallel for testing. Due to the inconsistent contact resistance of each probe, the current flowing through each probe will be inconsistent, causing the current of individual probes to exceed the rated current. This will cause the probe to burn out and the contact point to be destroyed.

[0003] Among the existing probe protection schemes, each probe has a resistor connected in series. In this scheme, a voltage drop will inevitably occur on the resistor connected in series. The greater the current, the greater the voltage drop. In the application of high current testing, such a voltage drop is unacceptable. In previous DC parameter tests, there are also schemes that use active devices to build negative feedback circuits to control the current of each probe, but due to the response speed of active devices, it cannot adapt to dynamic parameter tests with rapid current changes. Utility Model Content

[0004] Therefore, the technical problem to be solved by the utility model is to solve the problem in the prior art that the probe cannot adjust the current size when overcurrent occurs, resulting in the probe burning, thereby providing an overcurrent protection circuit and a power device testing device.

[0005] In order to achieve the above object, the utility model provides the following technical solutions:

[0006] In a first aspect, the utility model provides an overcurrent protection circuit, including: a current limiting circuit, a control circuit and an overcurrent detection circuit, wherein the control circuit, whose input end receives a control signal of an operating system, whose first output end and second output end are respectively connected to the first end and second end of the current limiting circuit, and which is used to set a threshold current of the current limiting circuit based on the control signal; the current limiting circuit, whose third end and fourth end are respectively connected to the first input end and second input end of the overcurrent detection circuit, and whose third end and fourth end are also respectively connected to the first end and second end of the probe; the overcurrent detection circuit, whose output end is connected to the operating system The system is connected, when the voltage at the third or fourth terminal of the current limiting circuit increases, the overcurrent detection circuit is turned on and sends an overcurrent signal to the operating system; when the current flowing through the probe is greater than the threshold current and the current direction is from the first end to the second end of the probe, the voltage at the fourth terminal of the current limiting circuit remains unchanged, and after the voltage at the third terminal increases, the current flowing through the probe is maintained at a preset current value; when the current flowing through the probe is greater than the threshold current and the current direction is from the second end to the first end of the probe, the voltage at the third terminal of the current limiting circuit remains unchanged, and after the voltage at the fourth terminal increases, the current flowing through the probe is maintained at a preset current value.

[0007] The overcurrent protection circuit provided by the utility model, when the current flowing through the probe is greater than the threshold current, no matter the direction of the overcurrent flows from the first end of the probe to the second end or from the second end of the probe to the first end, that is, no matter the current is forward or reverse, the current limiting circuit reduces the magnitude of the conduction current in the current limiting circuit by controlling the voltage increase at the third end or the fourth end, thereby reducing the magnitude of the current flowing through the probe, that is, the current limiting circuit can achieve bidirectional overcurrent protection for the probe by adjusting the magnitude of the current in the probe, avoid the probe being burned by the overcurrent, extend the service life of the probe, and make the application scenarios of the overcurrent protection circuit more extensive; the operator can set the threshold current of the current limiting circuit through the operating system, and the operating system can monitor the overcurrent situation of the probe based on the overcurrent signal, so that the operator can be aware of the overcurrent situation of the probe in time, troubleshoot in time, avoid the probe being unable to work for a long time due to overcurrent, and improve work efficiency.

[0008] In an optional embodiment, the control circuit includes: a digital isolator, a digital-to-analog converter and an amplifier circuit, wherein the digital isolator has a first end connected to the operating system and a second end connected to the first end of the digital-to-analog converter, and is used to isolate interference signals in the control signal; the digital-to-analog converter has a second end connected to the input end of the amplifier circuit, and is used to output a threshold voltage based on the control signal, thereby setting a threshold current of the current limiting circuit; the amplifier circuit has an output end connected to the first end of the current limiting circuit and a first end connected to the second end of the current limiting circuit, and is used to amplify the threshold voltage.

[0009] The overcurrent protection circuit and the digital isolator provided by the utility model can isolate the noise interference of the operating system, reduce the interference of the interference signal to the current limiting circuit, and improve the working accuracy of the current limiting circuit; the operator can set the threshold current of the current limiting circuit through the digital-to-analog converter, thereby setting the current upper limit of the probe, so that the probe can contact with devices with different current values ​​without being damaged by overcurrent, thereby extending the use range of the probe.

[0010] In an optional embodiment, the amplification circuit includes: an operational amplifier, whose input end is connected to the second end of the digital-to-analog converter, whose first output end is connected to the first end of the current limiting circuit, and whose second output end is connected to the second end of the current limiting circuit, and which is used to amplify the threshold voltage and input it into the current limiting circuit.

[0011] In an optional embodiment, the current limiting circuit includes: a first switch circuit and a second switch circuit, wherein the first switch circuit, a control end thereof is connected to the first output end of the control circuit and the control end of the second switch circuit, a first end thereof is connected to the first input end of the overcurrent detection circuit and the first end of the probe, and a second end thereof is connected to the second output end of the control circuit and the first end of the second switch circuit; the second switch circuit, a second end thereof is connected to the second input end of the overcurrent detection circuit and the second end of the probe; when the current flowing through the probe is greater than the threshold current and the current direction is from the first end to the second end of the probe, after the first switch circuit is turned off and the second switch circuit is turned on, the voltage at the first end of the first switch circuit increases, and the voltage at the second end of the second switch circuit remains unchanged, so that the current flowing through the probe is maintained at a preset current value; when the current flowing through the probe is greater than the threshold current and the current direction is from the second end to the first end of the probe, after the first switch circuit is turned on and the second switch circuit is turned off, the voltage at the first end of the first switch circuit remains unchanged, and the voltage at the second end of the second switch circuit increases, so that the current flowing through the probe is maintained at a preset current value.

[0012] The overcurrent protection circuit provided by the utility model has two switch circuits that can switch the on-off state according to the direction of the overcurrent, and reduce the current value flowing through the probe by increasing the voltage value at one end of the probe, thereby realizing bidirectional overcurrent protection for the probe. The protection method is simple and has high reliability.

[0013] In an optional embodiment, the first switching circuit includes: a first capacitor and a first switch, wherein the first capacitor, a first end of which is connected to the first output end of the control circuit, the control end of the first switch and the control end of the second switching circuit, and a second end of which is connected to the first output end of the control circuit, the second end of the first switch and the first end of the second switching circuit; the first switch, a first end of which is connected to the first input end of the overcurrent detection circuit and the first end of the probe.

[0014] In an optional embodiment, the second switching circuit includes: a second capacitor and a second switch, wherein the first end of the second capacitor is connected to the first end of the first capacitor, and the second end of the second capacitor is connected to the first end of the first capacitor and the control end of the second switch; the first end of the second switch is connected to the second end of the first switch, and the second end of the second switch is connected to the second input end of the overcurrent detection circuit and the second end of the probe.

[0015] In an optional embodiment, the overcurrent detection circuit includes: a differential operational amplifier and an isolation circuit, wherein the differential operational amplifier has a first input terminal connected to the third terminal of the current limiting circuit, a second input terminal connected to the fourth terminal of the current limiting circuit, and a first output terminal and a second output terminal connected to the first terminal and the second terminal of the isolation circuit respectively; an isolation circuit has a third terminal connected to an operating system; when the differential operational amplifier detects that the voltage at the third terminal or the fourth terminal of the current limiting circuit increases, the differential operational amplifier controls the isolation circuit to turn on, and then the differential operational amplifier outputs an overcurrent signal to the operating system.

[0016] The overcurrent protection circuit provided by the utility model can trigger the differential operational amplifier to output an overcurrent signal in different directions of overcurrent, thereby ensuring that the operating system can monitor the overcurrent situation in any direction of the probe according to the overcurrent signal, thereby achieving timely and comprehensive monitoring of the fault situation of the probe.

[0017] In an optional embodiment, the isolation circuit includes: a first isolation branch and a second isolation branch, wherein the first isolation branch, its first end, second end, third end and fourth end are respectively connected to the first end, second end, third end and fourth end of the second isolation branch, and its first end and second end are also respectively connected to the first output end and the second output end of the differential operational amplifier, and its third end and fourth end are both connected to the operating system; when the voltage at the first input end of the differential operational amplifier increases, the first isolation branch is turned on and the second isolation branch is cut off, and the differential operational amplifier outputs an overcurrent signal to the operating system through the first isolation branch; when the voltage at the second input end of the differential operational amplifier increases, the second isolation branch is turned on and the first isolation branch is cut off, and the differential operational amplifier outputs an overcurrent signal to the operating system through the second isolation branch.

[0018] The overcurrent protection circuit provided by the utility model can control one of them to be turned on and the other to be turned off when the probe triggers the overcurrent protection of the current limiting circuit, thereby ensuring that the isolation circuit is not affected by the overcurrent direction and can output the overcurrent signal to the operating system, so that the operating system can monitor the overcurrent situation in any direction of the probe, and timely and comprehensively monitor the fault situation of the probe.

[0019] In an optional implementation, the first isolation branch and the second isolation branch both include an optocoupler isolation chip.

[0020] In the second aspect, the utility model provides a power device testing device, comprising: a testing machine, a plurality of probes and a plurality of overcurrent protection circuits of the first aspect, wherein the first end and the second end of each probe are respectively connected to the third end and the fourth end of a current limiting circuit in an overcurrent protection circuit, and the third end of each probe is connected to the power device under test, and is used to transmit current information to the testing machine, so that the testing machine tests the performance of the power device under test based on the current information; the testing machine is connected to the input end of the control circuit in each overcurrent protection circuit, and is used to perform dynamic parameter testing on the power device under test through a plurality of probes, and to set the threshold current of the current limiting circuit and receive the overcurrent signal of the overcurrent detection circuit.

[0021] The utility model provides a power device testing device, in which each probe is provided with an overcurrent protection circuit, so that the test machine can set the current upper limit of the corresponding probe through the control circuit in each overcurrent protection circuit, and no matter what the direction of the current in the probe is, each current limiting circuit can immediately reduce the current flowing through the corresponding probe when the current is overcurrent, that is, the current limiting circuit can adjust the current in the probe to avoid the situation where the current on some probes exceeds the rated current of the probe and burns out due to inconsistent contact resistance of each probe, thereby realizing bidirectional overcurrent protection for the probe and extending the service life of the probe; the operator can also monitor the overcurrent situation of each probe in real time through the test machine while performing dynamic parameter testing on the power device, timely troubleshooting, and reducing the time and difficulty of troubleshooting. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 is a composition diagram of a specific example of an overcurrent protection circuit according to an embodiment of the utility model;

[0024] Figure 2 is a specific circuit diagram of an overcurrent protection circuit according to an embodiment of the utility model;

[0025] Figure 3 It is a composition diagram of a specific example of a power device testing device according to an embodiment of the utility model. DETAILED DESCRIPTION

[0026] The technical solution of the utility model will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0027] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0028] In the description of the present utility model, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0029] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] This embodiment provides an overcurrent protection circuit. Figure 1 As shown, it includes: a control circuit 1, a current limiting circuit 2 and an overcurrent detection circuit 3, wherein the control circuit 1, whose input end receives the control signal of the operating system, and whose first output end and second output end are respectively connected to the first end and the second end of the current limiting circuit 2, and is used to set the threshold current of the current limiting circuit 2 based on the control signal; the current limiting circuit 2, whose third end and fourth end are respectively connected to the first input end and the second input end of the overcurrent detection circuit 3, and whose third end and fourth end are also respectively connected to the first end and the second end of the probe; the overcurrent detection circuit, whose output end is connected to the operating system.

[0031] Figure 1In the embodiment, when the voltage at the third or fourth terminal of the current limiting circuit 2 increases, the overcurrent detection circuit 3 is turned on and sends an overcurrent signal to the operating system; when the current flowing through the probe is greater than the threshold current and the current direction is from the first end to the second end of the probe, the voltage at the fourth terminal of the current limiting circuit 2 remains unchanged and the voltage at the third terminal increases, so that the current flowing through the probe is maintained at a preset current value; when the current flowing through the probe is greater than the threshold current and the current direction is from the second end to the first end of the probe, the voltage at the third terminal of the current limiting circuit 2 remains unchanged and the voltage at the fourth terminal increases, so that the current flowing through the probe is maintained at a preset current value.

[0032] Specifically, Figure 1 As shown, the operator sets the threshold current of the current limiting circuit 2 by sending a control signal to the control circuit 1 through the operating system. When the current value flowing into the fourth end of the current limiting circuit exceeds the threshold current, that is, when the current flowing from the first end of the probe to the second end exceeds the threshold current, the circuit between the second end and the third end of the current limiting circuit 2 is disconnected, and the circuit between the second end and the fourth end is connected, so that the voltage of the third end of the current limiting circuit 2 increases and the voltage of the fourth end remains unchanged, thereby limiting the current flowing from the first end to the second end, so that the current flowing through the probe is maintained at a preset current value. At the same time, after the voltage of the third end of the current limiting circuit 2 increases, the high-level signal triggers the circuit between the first input end of the overcurrent detection circuit 3 and the operating system to be connected, and the overcurrent detection circuit 3 converts the high-level signal into an overcurrent signal and inputs it into the operating system.

[0033] Specifically, Figure 1 As shown, when the current value flowing into the third end of the current limiting circuit exceeds the threshold current, that is, when the current flowing from the second end to the first end of the probe exceeds the threshold current, the circuit between the second end and the fourth end of the current limiting circuit 2 is disconnected, and the circuit between the second end and the third end is turned on, so that the voltage of the fourth end of the current limiting circuit 2 increases and the voltage of the third end remains unchanged, thereby limiting the current flowing from the second end to the first end, so that the current flowing through the probe is maintained at a preset current value. At the same time, after the voltage of the fourth end of the current limiting circuit 2 increases, the high-level signal triggers the circuit between the second input end of the overcurrent detection circuit 3 and the operating system to be turned on, and the overcurrent detection circuit 3 converts the high-level signal into an overcurrent signal and inputs it into the operating system.

[0034] The overcurrent protection circuit provided in this embodiment, when the current flowing through the probe is greater than the threshold current, no matter the direction of the overcurrent flows from the first end to the second end of the probe or from the second end to the first end of the probe, the current limiting circuit reduces the magnitude of the conduction current in the current limiting circuit by controlling the voltage increase at the third end or the fourth end, that is, the current limiting circuit can reduce the magnitude of the current flowing through the probe by adjusting the magnitude of the current in the probe, thereby achieving bidirectional overcurrent protection for the probe, making the application scenarios of the overcurrent protection circuit more extensive; the operator can set the threshold current of the current limiting circuit through the operating system, and the operating system can monitor the overcurrent situation of the probe based on the overcurrent signal, so that the operator can be aware of the overcurrent situation of the probe in time, troubleshoot in time, and avoid the probe from being unable to work for a long time due to overcurrent, thereby improving work efficiency.

[0035] In some optional embodiments, such as Figure 2 As shown, the control circuit 1 includes: a digital isolator U1, a digital-to-analog converter U2 and an amplifier circuit 11, wherein the digital isolator U1, a first end of which is connected to the operating system, and a second end of which is connected to the first end of the digital-to-analog converter U2, and is used to isolate interference signals in the control signal; the digital-to-analog converter U2, a second end of which is connected to the input end of the amplifier circuit 11, and is used to output a threshold voltage based on the control signal, thereby setting the threshold current of the current limiting circuit 2; the amplifier circuit 11, an output end of which is connected to the first end of the current limiting circuit 2, a first end of which is connected to the second end of the current limiting circuit 2, and is used to amplify the threshold voltage.

[0036] For example, Figure 2 As shown, the amplifier circuit 11 includes: an operational amplifier OP1, whose input end is connected to the second end of the digital-to-analog converter U2, whose first output end is connected to the first end of the current limiting circuit 2, and whose second output end is connected to the second end of the current limiting circuit, and which is used to amplify the threshold voltage and input it into the current limiting circuit 2.

[0037] Specifically, the digital isolator U1 is used to isolate the noise interference of the operating system, reduce the interference of the interference signal to the current limiting circuit 2, and improve the working accuracy of the current limiting circuit 2; the digital-to-analog converter U2 can convert the digital signal in the control signal into an analog signal, output the threshold voltage of the current limiting circuit 2 according to the analog signal, and set the threshold current of the current limiting circuit 2 after amplifying the threshold voltage through the operational amplifier OP1.

[0038] It should be noted that those skilled in the art can choose whether to set the digital-to-analog converter U2 according to actual circuit characteristics, and no limitation is made here.

[0039] In some optional embodiments, such as Figure 2As shown, the current limiting circuit 2 includes: a first switch circuit 21 and a second switch circuit 22, wherein the first switch circuit 21 has a control end connected to the first output end of the control circuit 1 and the control end of the second switch circuit 22, a first end connected to the first input end of the overcurrent detection circuit 3 and the first end of the probe, and a second end connected to the second output end of the control circuit 1 and the first end of the second switch circuit 22; the second switch circuit 22 has a second end connected to the second input end of the overcurrent detection circuit 3 and the second end of the probe.

[0040] Figure 2 In the embodiment, when the current flowing through the probe is greater than the threshold current and the current direction is from the first end to the second end of the probe, after the first switch circuit 21 is turned off and the second switch circuit 22 is turned on, the voltage at the first end of the first switch circuit 21 increases, and the voltage at the second end of the second switch circuit 22 remains unchanged, so that the current flowing through the probe is maintained at a preset current value; when the current flowing through the probe is greater than the threshold current and the current direction is from the second end to the first end of the probe, after the first switch circuit 21 is turned on and the second switch circuit 22 is turned off, the voltage at the first end of the first switch circuit 21 remains unchanged, and the voltage at the second end of the second switch circuit 22 increases, so that the current flowing through the probe is maintained at a preset current value.

[0041] like Figure 2 As shown, the first switch circuit 21 includes: a first capacitor C1 and a first switch Q1, wherein the first capacitor C1, a first end thereof is connected to the first output end of the control circuit 1, the control end of the first switch Q1 and the control end of the second switch circuit 22, and a second end thereof is connected to the first output end of the control circuit 1, the second end of the first switch Q1 and the first end of the second switch circuit 22; the first switch Q1, a first end thereof is connected to the first input end of the overcurrent detection circuit 3 and the first end of the probe.

[0042] like Figure 2 As shown, the second switch circuit 22 includes: a second capacitor C2 and a second switch Q2, wherein the second capacitor C2 has a first end connected to the first end of the first capacitor C1, and a second end connected to the first end of the first capacitor C1 and the control end of the second switch Q2; the second switch Q2 has a first end connected to the second end of the first switch Q1, and a second end connected to the second input end of the overcurrent detection circuit 3 and the second end of the probe.

[0043] For example, Figure 2As shown, the first switch Q1 and the second switch Q2 are a pair of symmetrically arranged MOS tubes, that is, the sources of the two MOS tubes are connected together, which can realize bidirectional overcurrent protection for the probe; the first capacitor C1 is connected in parallel between the gate and the source of the first switch Q1, and the second capacitor C2 is connected in parallel between the gate and the source of the second switch Q2, which is used to increase the switching speed of the first switch Q1 and the second switch Q2. The operating system converts the digital signal for adjusting the gate voltage of the first switch Q1 and the second switch Q2 into an analog signal by adjusting the digital-to-analog converter U2, and then sets the gate voltage of the first switch Q1 and the second switch Q2. The magnitude of the gate voltage determines the pinch-off current of the first switch Q1 and the second switch Q2, that is, the threshold current of the probe is set. When the current value flowing through the probe is in the variable resistance region of the first switch Q1 and the second switch Q2, the first switch Q1 and the second switch Q2 are in the variable resistance state, and the first switch Q1 and the second switch Q2 are both maintained in the low resistance state and turned on.

[0044] For example, Figure 2 As shown, the first switch Q1 and the second switch Q2 are a pair of symmetrically arranged MOS tubes. When the current value flowing from the first end to the second end of the probe rises to the pinch-off region of the first switch Q1, that is, the current flowing from the first end to the second end of the probe exceeds the threshold current of the probe, the first switch Q1 is turned off, the second switch Q2 remains on, the voltage between the drain and the source of the first switch Q1 rises rapidly, no current flows into the first end of the probe on the operating system side, and the overcurrent in the probe is gradually consumed by the resistor in the probe to a preset current value and maintained at the preset current value; when the current value flowing from the second end to the first end of the probe rises to the pinch-off region of the second switch Q2, that is, the current flowing from the second end to the first end of the probe exceeds the threshold current of the probe, the second switch Q2 is turned off, the first switch Q1 remains on, the voltage between the drain and the source of the second switch Q2 rises rapidly, no current flows into the second end of the probe on the operating system side, and the overcurrent in the probe is gradually consumed by the resistor in the probe to a preset current value and maintained at the preset current value.

[0045] In some optional embodiments, such as Figure 2 As shown, the overcurrent detection circuit 3 includes: a differential operational amplifier OP2 and an isolation circuit 31, wherein the differential operational amplifier OP2 has a first input terminal connected to the third terminal of the current limiting circuit 2, a second input terminal connected to the fourth terminal of the current limiting circuit 2, and a first output terminal and a second output terminal connected to the first terminal and the second terminal of the isolation circuit 31 respectively; the isolation circuit 31 has a third terminal connected to the operating system; when the differential operational amplifier OP2 detects that the voltage at the third terminal or the fourth terminal of the current limiting circuit 2 increases, the differential operational amplifier controls the isolation circuit 31 to be turned on, and the differential operational amplifier OP2 outputs an overcurrent signal to the operating system.

[0046] like Figure 2As shown, the isolation circuit 31 includes: a first isolation branch U3 and a second isolation branch U4, wherein the first isolation branch U3 and the second isolation branch U4 both include an optical coupling isolation chip; the first isolation branch U3, its first end, second end, third end and fourth end are respectively connected to the first end, second end, third end and fourth end of the second isolation branch U4, and its first end and second end are also respectively connected to the first output end and the second output end of the differential operational amplifier OP2, and its third end and fourth end are both connected to the operating system; when the voltage at the first input end of the differential operational amplifier OP2 increases, the first isolation branch U3 is turned on and the second isolation branch U4 is turned off, and the differential operational amplifier OP2 outputs an overcurrent signal to the operating system through the first isolation branch U3; when the voltage at the second input end of the differential operational amplifier OP2 increases, the second isolation branch U4 is turned on and the first isolation branch U3 is turned off, and the differential operational amplifier OP2 outputs an overcurrent signal to the operating system through the second isolation branch U4.

[0047] Specifically, Figure 2 As shown, the two input signals of the differential operational amplifier OP2 are the voltage difference between the drains of the first switch Q1 and the second switch Q2. When the current in the probe is less than or equal to the threshold current, the first switch Q1 and the second switch Q2 both remain turned on, and the voltage difference between the drains is approximately 0V, that is, the voltage difference between the two input terminals of the differential operational amplifier OP2 is approximately 0V, and the differential operational amplifier OP2 outputs no overcurrent signal output, and the first isolation branch U3 and the second isolation branch U4 are both cut off.

[0048] Specifically, Figure 2 As shown, when the current flowing from the first end to the second end of the probe exceeds the threshold current of the probe, the first switch Q1 is turned off, the second switch Q2 remains turned on, the drain voltage of the first switch Q1 rises rapidly, the drain voltage of the second switch Q2 is about 0V, the voltage at the negative input terminal of the differential operational amplifier OP2 is higher than the voltage at the positive input terminal, the differential operational amplifier OP2 outputs a negative voltage overcurrent signal to turn on the first isolation branch U3 and turn off the second isolation branch U4, and the overcurrent signal is input to the operating system through the first isolation branch U3 and the pull-up resistor R2. When the current flowing from the second end of the probe to the first end exceeds the threshold current of the probe, the second switch Q2 is turned off, the first switch Q1 remains on, the drain voltage of the second switch Q2 rises rapidly, the drain voltage of the first switch Q1 is about 0V, the voltage at the positive input terminal of the differential operational amplifier OP2 is higher than the voltage at the negative input terminal, the differential operational amplifier OP2 outputs a positive voltage overcurrent signal to turn on the second isolation branch U4 and turn off the first isolation branch U3, and the overcurrent signal is input to the operating system through the second isolation branch U4 and the pull-up resistor R2.

[0049] The present embodiment provides a power device testing device, comprising: a test machine 4, multiple probes and multiple overcurrent protection circuits CLAMP of the above embodiments and any optional implementation methods thereof, wherein the first end and the second end of each probe are respectively connected to the third end and the fourth end of a current limiting circuit 2 in an overcurrent protection circuit, and the third end of each probe is connected to the power device under test, and is used to transmit current information to the test machine 4, so that the test machine 4 tests the performance of the power device under test based on the current information; the test machine 4 is connected to the input end of the control circuit 1 in each overcurrent protection circuit, and is used to perform dynamic parameter testing on the power device under test through multiple probes, and to set the threshold current of the current limiting circuit 2 and receive the overcurrent signal of the overcurrent detection circuit 3.

[0050] Specifically, Figure 3 As shown, one end of each probe in the power device test device is set on the probe needle card, one end of the power device to be tested is placed on the probe table, and the other end is in contact with each probe. The test machine performs dynamic parameter testing on the power device to be tested through the probe. Each probe is connected to an overcurrent protection circuit CLAMP, the current limiting circuit 2 is responsible for limiting the current flowing through the probe, the control circuit 1 is responsible for adjusting the current threshold in the probe, and the overcurrent detection circuit 3 will notify the test machine 4 when the probe is overcurrent. When the probe is overcurrent, no matter whether the direction of the overcurrent flows from the first end of the probe to the second end, or from the second end of the probe to the first end, the current limiting circuit 2 in the overcurrent protection circuit CLAMP can limit the current of the probe to achieve bidirectional overcurrent protection of the probe, and the test machine 4 can receive the overcurrent signal sent by the overcurrent protection circuit CLAMP, and the operator can troubleshoot the overcurrent probe through the test machine 4.

[0051] It should be noted that the test machine 4 controls the overcurrent protection circuit CLAMP by digital control, which has higher reliability than analog signals and avoids distortion during signal transmission. The process of the overcurrent protection circuit CLAMP protecting the probe from overcurrent and the test machine 4 receiving the overcurrent signal is the same as the above embodiment and any optional implementation method thereof, and will not be repeated here.

[0052] For example, Figure 2 As shown, each probe is connected to the current limiting circuit 2 through nH-level distributed inductors L1 and L2. The distributed inductors can improve the transmission and reception of high-frequency signals in the circuit between the tester and the probe, and improve the effect and accuracy of the tester 4 on the dynamic parameter testing of the power device under test.

[0053] In the power device testing device provided in the present embodiment, each probe is provided with an overcurrent protection circuit, so that the tester can set the current upper limit of the corresponding probe through the control circuit in each overcurrent protection circuit, so that when the power device is tested, it is possible to avoid the situation where the current on some probes exceeds the rated current of the probes and burns out due to inconsistent contact resistance of each probe, and the operation is convenient; the operator can also monitor the overcurrent situation of each probe in real time through the tester, troubleshoot in time, and reduce the time and difficulty of troubleshooting.

[0054] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. An overcurrent protection circuit, characterized in that: include: Current limiting circuit, control circuit and overcurrent detection circuit, among which, A control circuit, whose input end receives a control signal of an operating system, whose first output end and second output end are respectively connected to the first end and the second end of the current limiting circuit, and which is used to set a threshold current of the current limiting circuit based on the control signal; A current limiting circuit, wherein the third end and the fourth end are connected to the first input end and the second input end of the overcurrent detection circuit respectively, and the third end and the fourth end are also connected to the first end and the second end of the probe respectively; An overcurrent detection circuit, whose output end is connected to the operating system, when the voltage at the third end or the fourth end of the current limiting circuit increases, the overcurrent detection circuit is turned on and sends an overcurrent signal to the operating system; When the current flowing through the probe is greater than the threshold current and the current flows from the first end to the second end of the probe, the voltage at the fourth end of the current limiting circuit remains unchanged and the voltage at the third end increases, so that the current flowing through the probe is maintained at a preset current value; When the current flowing through the probe is greater than the threshold current and the current direction is from the second end to the first end of the probe, the voltage at the third end of the current limiting circuit remains unchanged and the voltage at the fourth end increases, so that the current flowing through the probe is maintained at a preset current value.

2. The overcurrent protection circuit according to claim 1, characterized in that: The control circuit includes: a digital isolator, a digital-to-analog converter and an amplifier circuit, wherein: A digital isolator, a first end of which is connected to the operating system, a second end of which is connected to the first end of the digital-to-analog converter, and is used to isolate interference signals in the control signal; a digital-to-analog converter, a second end of which is connected to the input end of the amplifier circuit, and is used to output a threshold voltage based on the control signal, thereby setting a threshold current of the current limiting circuit; An amplifier circuit, whose output end is connected to the first end of the current limiting circuit and whose first end is connected to the second end of the current limiting circuit, is used to amplify the threshold voltage.

3. The overcurrent protection circuit according to claim 2, characterized in that: The amplifying circuit comprises: An operational amplifier, whose input end is connected to the second end of the digital-to-analog converter, whose first output end is connected to the first end of the current limiting circuit, and whose second output end is connected to the second end of the current limiting circuit, is used to amplify the threshold voltage and input it into the current limiting circuit.

4. The overcurrent protection circuit according to claim 1, characterized in that: The current limiting circuit includes: a first switch circuit and a second switch circuit, wherein: A first switch circuit, whose control end is connected to the first output end of the control circuit and the control end of the second switch circuit, whose first end is connected to the first input end of the overcurrent detection circuit and the first end of the probe, and whose second end is connected to the second output end of the control circuit and the first end of the second switch circuit; A second switch circuit, a second end of which is connected to the second input end of the overcurrent detection circuit and the second end of the probe; When the current flowing through the probe is greater than the threshold current and the current direction is from the first end to the second end of the probe, after the first switch circuit is turned off and the second switch circuit is turned on, the voltage at the first end of the first switch circuit increases and the voltage at the second end of the second switch circuit remains unchanged, so that the current flowing through the probe is maintained at a preset current value; When the current flowing through the probe is greater than the threshold current and the current direction is from the second end to the first end of the probe, after the first switch circuit is turned on and the second switch circuit is turned off, the voltage at the first end of the first switch circuit remains unchanged and the voltage at the second end of the second switch circuit increases, so that the current flowing through the probe is maintained at a preset current value.

5. The overcurrent protection circuit according to claim 4, characterized in that: The first switch circuit includes: a first capacitor and a first switch, wherein: a first capacitor, a first end of which is connected to the first output end of the control circuit, the control end of the first switch and the control end of the second switch circuit, and a second end of which is connected to the first output end of the control circuit, the second end of the first switch and the first end of the second switch circuit; A first switch has a first end connected to a first input end of the overcurrent detection circuit and a first end of the probe.

6. The overcurrent protection circuit according to claim 5, characterized in that: The second switch circuit includes: a second capacitor and a second switch, wherein: A second capacitor, a first end of which is connected to the first end of the first capacitor, and a second end of which is connected to the first end of the first capacitor and the control end of the second switch; A second switch has a first end connected to the second end of the first switch, and a second end connected to the second input end of the overcurrent detection circuit and the second end of the probe.

7. The overcurrent protection circuit according to claim 1, characterized in that: The overcurrent detection circuit comprises: a differential operational amplifier and an isolation circuit, wherein: a differential operational amplifier, wherein a first input terminal of the differential operational amplifier is connected to the third terminal of the current limiting circuit, a second input terminal of the differential operational amplifier is connected to the fourth terminal of the current limiting circuit, and a first output terminal and a second output terminal of the differential operational amplifier are connected to the first terminal and the second terminal of the isolation circuit respectively; an isolation circuit, a third terminal of which is connected to the operating system; When the differential operational amplifier detects that the voltage at the third terminal or the fourth terminal of the current limiting circuit increases, the differential operational amplifier controls the isolation circuit to be turned on, and then the differential operational amplifier outputs an overcurrent signal to the operating system.

8. The overcurrent protection circuit according to claim 7, characterized in that: The isolation circuit comprises: a first isolation branch and a second isolation branch, wherein: a first isolation branch, wherein the first end, the second end, the third end and the fourth end are respectively connected to the first end, the second end, the third end and the fourth end of the second isolation branch, the first end and the second end are also respectively connected to the first output end and the second output end of the differential operational amplifier, and the third end and the fourth end are both connected to the operating system; When the voltage at the first input terminal of the differential operational amplifier increases, the first isolation branch is turned on and the second isolation branch is turned off, and the differential operational amplifier outputs an overcurrent signal to the operating system through the first isolation branch; When the voltage at the second input terminal of the differential operational amplifier increases, the second isolation branch is turned on and the first isolation branch is turned off, and the differential operational amplifier outputs an overcurrent signal to the operating system through the second isolation branch.

9. The overcurrent protection circuit according to claim 8, characterized in that: The first isolation branch and the second isolation branch both include an optocoupler isolation chip.

10. A power device testing device, characterized in that: include: A test machine, a plurality of probes and a plurality of overcurrent protection circuits according to any one of claims 1 to 9, wherein: The first end and the second end of each probe are respectively connected to the third end and the fourth end of the current limiting circuit in an overcurrent protection circuit, and the third end of each probe is connected to the power device under test, which is used to transmit the current information to the tester, so that the tester tests the performance of the power device under test based on the current information; The test machine is connected to the input end of the control circuit in each overcurrent protection circuit, and is used to perform dynamic parameter testing on the power device under test through multiple probes, set the threshold current of the current limiting circuit, and receive the overcurrent signal of the overcurrent detection circuit.

Images