A si c mosfet threshold voltage monitoring system and method

Abstract

The application provides a SiC Mosfet threshold voltage monitoring system and method, and belongs to the technical field of SiC Mosfet threshold voltage monitoring.The controller is connected with a driving module and a switching module respectively; the driving module is connected with the switching module; the switching module is connected with a test loop; the test loop is connected with a threshold voltage collection module; the controller controls the driving module, the driving module drives the switching module to act, and the action of the switching module switches the test loop between a test pulse preprocessing circuit and a threshold voltage detection circuit.The application considers the recovery effect, applies a preprocessing pulse before the test pulse, makes the measured threshold voltage more accurate, realizes the fast switching between the test pulse preprocessing circuit and the threshold voltage test loop, controls the pulse width and the power-on interval time by the controller, the precision is controllable, and the test requirements are met.

Description

Technical Field

[0001] This invention relates to the field of threshold voltage monitoring technology for SiC MOSFETs, and more particularly to a threshold voltage monitoring system and method for SiC MOSFET gate bias experiments. Background Technology

[0002] During normal operation, the threshold voltage of a SiC MOSFET may drift slightly due to defects at the semiconductor-oxide interface and / or charging / discharging. Since this drift typically shifts towards larger voltage values, it leads to increased on-resistance. This, in turn, increases losses and heat dissipation requirements, potentially shortening the device's lifespan.

[0003] Threshold voltage (VT) is a key parameter for evaluating the change in device characteristics under gate bias stress. Without accurate measurement of the threshold voltage, it is impossible to monitor how dynamic stress applied to the device alters its characteristics.

[0004] Typical circuit for MOSFET threshold voltage testing Figure 1 As shown. Test principle: DS is shorted, and a specified current IDS is input to SMU1. The Vge under this current is measured, which is the threshold voltage VT.

[0005] Chinese patent application CN101825680B discloses a threshold voltage measurement method and system. By obtaining the subthreshold slope of a semiconductor device, stress is applied to the device, and the linear leakage current of the device is measured at the threshold measurement time point. Based on the subthreshold slope and the linear leakage current value, the threshold voltage at the threshold measurement time point is calculated.

[0006] Chinese patent application CN110763972B discloses a method for measuring the threshold voltage of a MOSFET. The method involves setting a gate voltage measurement range based on an initial threshold voltage, measuring the static transfer characteristic curve of the linear operating region of the MOSFET within the gate voltage measurement range, thereby obtaining the maximum transconductance value and linearly extrapolating it to form the final threshold voltage.

[0007] Chinese patent application CN103576065B discloses a test circuit for the threshold voltage of a transistor. A switching circuit is added to the test circuit to control the device under test (DUT) to be in a stress state when the circuit is open and in a measurement state when the test circuit is closed. The threshold voltage of the DUT is calculated from the above two states.

[0008] Chinese patent application CN109782147A discloses a high-temperature gate bias test method for silicon carbide MOSFETs. By selecting a positive or negative scanning mode, a rapid switching between gate bias voltage shutdown and threshold voltage test is achieved through an electronic switch. The threshold voltage is tested at the instant t0 when the gate voltage is turned off.

[0009] The existing technology has at least the following shortcomings:

[0010] 1. The effects of NBTI recovery effect and PBTI recovery effect were not fully considered. Summary of the Invention

[0011] To address the technical problems existing in the prior art, this invention provides a SiC MOSFET threshold voltage monitoring system and method, comprising: a controller, a switching module, a driving module, a test circuit, a threshold voltage acquisition module, and a power supply module; the power supply module supplies power to the controller, the switching module, and the driving module; the controller is connected to the driving module and the switching module respectively; the driving module is connected to the switching module; the switching module is connected to the test circuit; the test circuit is connected to the threshold voltage acquisition module; the controller controls the driving module, which in turn causes the switching module to operate, and the operation of the switching module causes the test circuit to operate in the test pulse preprocessing circuit and the threshold voltage acquisition module. The switching module switches between voltage detection circuits, and the operation of the switching module is completed within hundreds of microseconds. The switching module includes multiple relays, which control the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 respectively. The first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 are all switches of the relays in the switching module. When the test circuit is a threshold voltage detection circuit, the threshold voltage acquisition module acquires the threshold voltage of the test circuit. The test pulse preprocessing circuit applies a preprocessing pulse before the test pulse and sets an interval time between the preprocessing pulse and the test pulse. The test circuit includes the SiC MOSFET under test and peripheral circuits. When the first switch K1 and the second switch K2 are closed and the third switch K3 and the fourth switch K4 are open, the test circuit is the test pulse preprocessing circuit. When the first switch K1 and the second switch K2 are open and the third switch K3 and the fourth switch K4 are closed, the test circuit is the threshold voltage detection circuit. This invention takes into account the recovery effect and applies a preprocessing pulse before the test pulse to make the measured threshold voltage more accurate. It realizes rapid switching between the test pulse preprocessing circuit and the threshold voltage test circuit. The pulse width and power-on interval are controlled by the controller, and the accuracy is controllable to meet the test requirements.

[0012] This invention provides a SiC MOSFET threshold voltage monitoring system, comprising: a controller, a switching module, a driving module, a test circuit, a threshold voltage acquisition module, and a power supply module;

[0013] The power supply module provides power to the controller, the switch module, and the drive module;

[0014] The controller is connected to the drive module and the switch module respectively; the drive module is connected to the switch module; the switch module is connected to the test circuit; the test circuit is connected to the threshold voltage acquisition module.

[0015] The controller controls the drive module, which in turn activates the switch module. The activation of the switch module causes the test circuit to switch between the test pulse preprocessing circuit and the threshold voltage detection circuit. The activation of the switch module is completed within 100 microseconds. The switch module includes multiple relays, which control a first switch K1, a second switch K2, a third switch K3, and a fourth switch K4, respectively. Each of the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 is a switch of a relay in the switch module.

[0016] When the test circuit is a threshold voltage detection circuit, the threshold voltage acquisition module acquires the threshold voltage of the test circuit;

[0017] The test pulse preprocessing circuit applies a preprocessing pulse before the test pulse and sets an interval time between the preprocessing pulse and the test pulse;

[0018] The test circuit includes the SiC MOSFET under test and peripheral circuits. When the first switch K1 and the second switch K2 are closed and the third switch K3 and the fourth switch K4 are open, the test circuit is the test pulse preprocessing circuit; when the first switch K1 and the second switch K2 are open and the third switch K3 and the fourth switch K4 are closed, the test circuit is the threshold voltage detection circuit.

[0019] Preferably, the width t_con of the preprocessing pulse is 1-100ms.

[0020] Preferably, the interval t_float between the preprocessing pulse and the test pulse is less than 10ms.

[0021] Preferably, the width of the test pulse t_VT < 10ms.

[0022] Preferably, the switching module includes multiple spring relays or multiple high-frequency relays.

[0023] Preferably, the operating time of the spring relay or high-frequency relay is within 100 microseconds.

[0024] Preferably, the first terminal of the first switch K1 is connected to the first terminal of the third switch K3 and the gate of the SiC MOSFET under test; the second terminal of the third switch K3 is connected to the first terminal of the second switch K2, the first terminal of the fourth switch K4 and the drain of the SiC MOSFET under test; the second terminal of the second switch K2 is grounded, the second segment of the fourth switch K4 is connected to the positive terminal of the constant current source, and the negative terminal of the constant current source is grounded.

[0025] Preferably, the switching module includes a first resistor, a first capacitor, a second resistor, and a first transistor. The first resistor is connected to the gate of the first transistor. When the test circuit is the threshold voltage detection circuit, the test pulse is input to the gate of the first transistor through the first resistor. The drain of the first transistor is connected to the first switch K1 and the second switch K2 respectively. The drain of the first transistor is also connected to the second resistor. The second resistor and the first capacitor are connected in series and then in parallel with the second switch K2.

[0026] This invention provides a method for monitoring the threshold voltage of a SiC MOSFET, employing any of the aforementioned SiC MOSFET threshold voltage monitoring systems, and includes the following steps:

[0027] Step 101: At the first preset time point t1, the controller controls the drive module to output a high-level signal VP0 of the preprocessing pulse. The pulse width of the preprocessing pulse is t_con. The high-level signal VP0 of the preprocessing pulse is applied to the gate of the SiC MOSFET of the sample under test.

[0028] Step 102, at the second preset time point t2, t2=t1+t_con, the controller controls the drive module to output a high-level signal VP1 of the test pulse, the relay of the first switch K1 is energized, the relay coil of the third switch K3 is energized, and the relay of the second switch K2 is energized after the interval time t_float, t2+t_float=t3;

[0029] Step 103: At time point t3, the relay of the second switch K2 is energized, which energizes the relay coil of the fourth switch K4 to detect the threshold voltage.

[0030] Preferably, the duration of t_con is controlled by a controller, which in turn controls the pulse width t_VT of the test pulse.

[0031] Compared with the prior art, the present invention has at least the following beneficial effects:

[0032] 1. This invention takes into account the recovery effect and applies a pre-processing pulse before the test pulse to remove the SiC / SiO2 interface from the unstable charge state, which solves the problem of poor stability of existing gate threshold voltage tests and improves the accuracy of the measured threshold voltage.

[0033] 2. The switching module of the present invention includes a spring-type or high-frequency relay. The action time of the spring-type or high-frequency relay is within 100 microseconds, which ensures rapid switching between the test pulse preprocessing circuit and the threshold voltage test circuit, and solves the problem of the stringent test time requirement for SiCMosfet threshold voltage test.

[0034] 3. This invention controls the timing of VP0 and VP1, and combines relays and RC circuits to set the width t_con of the preprocessing pulse, the width t_VT of the test pulse, and the interval time t_float between the preprocessing pulse and the test pulse. It can also precisely control the delay so that t_con, t_VT, and t_float meet the test requirements, simplify the design of peripheral circuits, and improve the anti-interference capability of the test equipment.

[0035] 4. When the first switch K1 and the second switch K2 are closed and the third switch K3 and the fourth switch K4 are open, the test circuit is a test pulse preprocessing circuit; when the first switch K1 and the second switch K2 are open and the third switch K3 and the fourth switch K4 are closed, the test circuit is a threshold voltage detection circuit. This simplifies the threshold voltage detection circuit and allows it to be directly integrated into existing high-temperature grid biasing equipment, solving the problem of insufficient threshold voltage detection capability in high-temperature grid biasing test equipment. Attached Figure Description

[0036] Figure 1 This is a typical circuit diagram for MOSFET threshold voltage testing, where iDS is the test current, source is the source of the MOSFET, GATE is the gate of the MOSFET, Drain is the drain of the MOSFET, SMU1 is the source measurement unit, and VT is the threshold voltage input current IDS.

[0037] Figure 2 This is a schematic diagram of a threshold voltage test waveform with preprocessing according to an embodiment of the present invention. In the figure, VDS is the voltage between the drain and source of the MOSFET, VGS is the voltage between the gate and source of the MOSFET, and VGS_max is the maximum voltage between the gate and source of the MOSFET.

[0038] Figure 3 This is a block diagram of a SiC MOSFET threshold voltage monitoring system according to an embodiment of the present invention;

[0039] Figure 4The test circuit of one embodiment of the present invention is a test pulse preprocessing circuit;

[0040] Figure 5 The circuit diagram shows a threshold voltage detection circuit as the test circuit of one embodiment of the present invention;

[0041] Figure 6 This is a circuit schematic diagram of a switching module according to an embodiment of the present invention;

[0042] Figure 7 This is a circuit diagram of a test circuit according to an embodiment of the present invention;

[0043] Figure 8 This is a schematic diagram of the relay operation timing in a SiC MOSFET threshold voltage monitoring method according to an embodiment of the present invention. Detailed Implementation

[0044] The following is in conjunction with the appendix Figure 1-8 The specific embodiments of the present invention will be described in detail below.

[0045] This invention provides a SiC MOSFET threshold voltage monitoring system, comprising: a controller, a switching module, a driving module, a test circuit, a threshold voltage acquisition module, and a power supply module;

[0046] The power supply module provides power to the controller, the switch module, and the drive module;

[0047] The controller is connected to the drive module and the switch module respectively; the drive module is connected to the switch module; the switch module is connected to the test circuit; the test circuit is connected to the threshold voltage acquisition module.

[0048] The controller controls the drive module, which in turn activates the switch module. The activation of the switch module causes the test circuit to switch between the test pulse preprocessing circuit and the threshold voltage detection circuit. The activation of the switch module is completed within 100 microseconds. The switch module includes multiple relays, which control a first switch K1, a second switch K2, a third switch K3, and a fourth switch K4, respectively. Each of the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 is a switch of a relay in the switch module.

[0049] When the test circuit is a threshold voltage detection circuit, the threshold voltage acquisition module acquires the threshold voltage of the test circuit;

[0050] The test pulse preprocessing circuit applies a preprocessing pulse before the test pulse and sets an interval time between the preprocessing pulse and the test pulse;

[0051] The test circuit includes the SiC MOSFET under test and peripheral circuits. When the first switch K1 and the second switch K2 are closed and the third switch K3 and the fourth switch K4 are open, the test circuit is the test pulse preprocessing circuit; when the first switch K1 and the second switch K2 are open and the third switch K3 and the fourth switch K4 are closed, the test circuit is the threshold voltage detection circuit.

[0052] Due to the recovery effect, the threshold voltage (VT) of a SiC MOSFET inherently varies with the device gate bias duration and measurement speed. Therefore, a standardized adjustment procedure is needed to stabilize the VT reading, thereby obtaining more consistent threshold voltage VT information in SiC MOSFET gate bias tests. If VT is measured directly without preprocessing, the SiC / SiO2 interface may be in an unstable charge state at the time of VT readout, potentially leading to erroneous VT drift assessments. To remove the SiC / SiO2 interface from an unstable charge state when detecting the threshold voltage VT, a preprocessing pulse can be applied before the test pulse.

[0053] According to a specific embodiment of the present invention, the width t_con of the preprocessing pulse is 1-100ms.

[0054] According to a specific embodiment of the present invention, the interval time t_float set between the preprocessing pulse and the test pulse is <10ms.

[0055] According to one specific embodiment of the present invention, the width of the test pulse t_VT < 10ms.

[0056] According to one specific embodiment of the present invention, the switching module includes multiple spring relays or multiple high-frequency relays.

[0057] According to a specific embodiment of the present invention, the operating time of the spring relay or high-frequency relay is within 100 microseconds.

[0058] According to a specific embodiment of the present invention, the first terminal of the first switch K1 is connected to the first terminal of the third switch K3 and the gate of the SiC MOSFET under test; the second terminal of the third switch K3 is connected to the first terminal of the second switch K2, the first terminal of the fourth switch K4 and the drain of the SiC MOSFET under test; the second terminal of the second switch K2 is grounded, the second segment of the fourth switch K4 is connected to the positive terminal of the constant current source, and the negative terminal of the constant current source is grounded.

[0059] According to a specific embodiment of the present invention, the switching module includes a first resistor, a first capacitor, a second resistor, and a first transistor. The first resistor is connected to the gate of the first transistor. When the test circuit is the threshold voltage detection circuit, the test pulse is input to the gate of the first transistor through the first resistor. The drain of the first transistor is connected to the first switch K1 and the second switch K2 respectively. The drain of the first transistor is also connected to the second resistor. The second resistor and the first capacitor are connected in series and then in parallel with the second switch K2.

[0060] This invention provides a method for monitoring the threshold voltage of a SiC MOSFET, employing any of the aforementioned SiC MOSFET threshold voltage monitoring systems, and includes the following steps:

[0061] Step 101: At the first preset time point t1, the controller controls the drive module to output a high-level signal VP0 of the preprocessing pulse. The pulse width of the preprocessing pulse is t_con. The high-level signal VP0 of the preprocessing pulse is applied to the gate of the SiC MOSFET of the sample under test.

[0062] Step 102, at the second preset time point t2, t2=t1+t_con, the controller controls the drive module to output a high-level signal VP1 of the test pulse, the relay of the first switch K1 is energized, the relay coil of the third switch K3 is energized, and the relay of the second switch K2 is energized after the interval time t_float, t2+t_float=t3;

[0063] Step 103: At time point t3, the relay of the second switch K2 is energized, which energizes the relay coil of the fourth switch K4 to detect the threshold voltage.

[0064] According to a specific embodiment of the present invention, the duration of t_con is controlled by a controller, which controls the pulse width t_VT of the test pulse.

[0065] Example 1

[0066] According to a specific embodiment of the present invention, the SiC MOSFET threshold voltage monitoring system of the present invention will be described in detail.

[0067] This invention provides a SiC MOSFET threshold voltage monitoring system, comprising: a controller, a switching module, a driving module, a test circuit, a threshold voltage acquisition module, and a power supply module;

[0068] The power supply module provides power to the controller, the switch module, and the drive module;

[0069] The controller is connected to the drive module and the switch module respectively; the drive module is connected to the switch module; the switch module is connected to the test circuit; the test circuit is connected to the threshold voltage acquisition module.

[0070] The controller controls the drive module, which in turn activates the switch module. The activation of the switch module causes the test circuit to switch between the test pulse preprocessing circuit and the threshold voltage detection circuit. The activation of the switch module is completed within 100 microseconds. The switch module includes multiple relays, which control a first switch K1, a second switch K2, a third switch K3, and a fourth switch K4, respectively. Each of the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 is a switch of a relay in the switch module.

[0071] When the test circuit is a threshold voltage detection circuit, the threshold voltage acquisition module acquires the threshold voltage of the test circuit;

[0072] The test pulse preprocessing circuit applies a preprocessing pulse before the test pulse and sets an interval time between the preprocessing pulse and the test pulse;

[0073] The test circuit includes the SiC MOSFET under test and peripheral circuits. When the first switch K1 and the second switch K2 are closed and the third switch K3 and the fourth switch K4 are open, the test circuit is the test pulse preprocessing circuit; when the first switch K1 and the second switch K2 are open and the third switch K3 and the fourth switch K4 are closed, the test circuit is the threshold voltage detection circuit.

[0074] The controller controls the drive module, causing the switching module to operate. The switching module switches the test circuit between the test pulse preprocessing circuit and the threshold voltage detection circuit, with the SiC MOSFET sample under test located within the test circuit. In threshold voltage detection circuit mode, the threshold voltage is detected in conjunction with the threshold voltage acquisition module.

[0075] Example 2

[0076] According to a specific embodiment of the present invention, the SiC MOSFET threshold voltage monitoring system of the present invention will be described in detail.

[0077] This invention provides a SiC MOSFET threshold voltage monitoring system, comprising: a controller, a switching module, a driving module, a test circuit, a threshold voltage acquisition module, and a power supply module;

[0078] The power supply module provides power to the controller, the switch module, and the drive module;

[0079] The controller is connected to the drive module and the switch module respectively; the drive module is connected to the switch module; the switch module is connected to the test circuit; the test circuit is connected to the threshold voltage acquisition module.

[0080] The controller controls the drive module, which in turn activates the switch module. The activation of the switch module causes the test circuit to switch between the test pulse preprocessing circuit and the threshold voltage detection circuit. The activation of the switch module is completed within 100 microseconds. The switch module includes multiple relays, which control a first switch K1, a second switch K2, a third switch K3, and a fourth switch K4, respectively. Each of the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 is a switch of a relay in the switch module.

[0081] When the test circuit is a threshold voltage detection circuit, the threshold voltage acquisition module acquires the threshold voltage of the test circuit;

[0082] The test pulse preprocessing circuit applies a preprocessing pulse before the test pulse and sets an interval time between the preprocessing pulse and the test pulse;

[0083] The test circuit includes the SiC MOSFET under test and peripheral circuits. When the first switch K1 and the second switch K2 are closed and the third switch K3 and the fourth switch K4 are open, the test circuit is the test pulse preprocessing circuit; when the first switch K1 and the second switch K2 are open and the third switch K3 and the fourth switch K4 are closed, the test circuit is the threshold voltage detection circuit.

[0084] The first terminal of the first switch K1 is connected to the first terminal of the third switch K3 and the gate of the SiC MOSFET under test; the second terminal of the third switch K3 is connected to the first terminal of the second switch K2, the first terminal of the fourth switch K4 and the drain of the SiC MOSFET under test; the second terminal of the second switch K2 is grounded, the second terminal of the fourth switch K4 is connected to the positive terminal of the constant current source, and the negative terminal of the constant current source is grounded.

[0085] The switching module includes a first resistor, a first capacitor, a second resistor, and a first transistor. The first resistor is connected to the gate of the first transistor. When the test circuit is the threshold voltage detection circuit, the test pulse is input to the gate of the first transistor through the first resistor. The drain of the first transistor is connected to the first switch K1 and the second switch K2 respectively. The drain of the first transistor is also connected to the second resistor. The second resistor and the first capacitor are connected in series and then in parallel with the second switch K2.

[0086] Example 3

[0087] According to a specific embodiment of the present invention, the SiC MOSFET threshold voltage monitoring system of the present invention will be described in detail.

[0088] This invention provides a SiC MOSFET threshold voltage monitoring system, comprising: a controller, a switching module, a driving module, a test circuit, a threshold voltage acquisition module, and a power supply module;

[0089] The power supply module provides power to the controller, the switch module, and the drive module;

[0090] The controller is connected to the drive module and the switch module respectively; the drive module is connected to the switch module; the switch module is connected to the test circuit; the test circuit is connected to the threshold voltage acquisition module.

[0091] The controller controls the drive module, which in turn activates the switch module. The activation of the switch module causes the test circuit to switch between the test pulse preprocessing circuit and the threshold voltage detection circuit. The activation of the switch module is completed within 100 microseconds. The switch module includes multiple relays, which control a first switch K1, a second switch K2, a third switch K3, and a fourth switch K4, respectively. Each of the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4 is a switch of a relay in the switch module.

[0092] When the test circuit is a threshold voltage detection circuit, the threshold voltage acquisition module acquires the threshold voltage of the test circuit;

[0093] The test pulse preprocessing circuit applies a preprocessing pulse before the test pulse and sets an interval time between the preprocessing pulse and the test pulse;

[0094] The test circuit includes the SiC MOSFET under test and peripheral circuits. When the first switch K1 and the second switch K2 are closed and the third switch K3 and the fourth switch K4 are open, the test circuit is the test pulse preprocessing circuit; when the first switch K1 and the second switch K2 are open and the third switch K3 and the fourth switch K4 are closed, the test circuit is the threshold voltage detection circuit.

[0095] The first terminal of the first switch K1 is connected to the first terminal of the third switch K3 and the gate of the SiC MOSFET under test; the second terminal of the third switch K3 is connected to the first terminal of the second switch K2, the first terminal of the fourth switch K4 and the drain of the SiC MOSFET under test; the second terminal of the second switch K2 is grounded, the second terminal of the fourth switch K4 is connected to the positive terminal of the constant current source, and the negative terminal of the constant current source is grounded.

[0096] The switching module includes a first resistor, a first capacitor, a second resistor, and a first transistor. The first resistor is connected to the gate of the first transistor. When the test circuit is the threshold voltage detection circuit, the test pulse is input to the gate of the first transistor through the first resistor. The drain of the first transistor is connected to the first switch K1 and the second switch K2 respectively. The drain of the first transistor is also connected to the second resistor. The second resistor and the first capacitor are connected in series and then in parallel with the second switch K2.

[0097] The width t_con of the preprocessing pulse is 1-100ms, the interval t_float between the preprocessing pulse and the test pulse is less than 10ms, and the width t_VT of the test pulse is less than 10ms.

[0098] The switching module includes multiple spring relays or multiple high-frequency relays.

[0099] The operating time of the spring relay or high-frequency relay is within 100 microseconds.

[0100] The switching module includes a spring-type or high-frequency relay, and the operating time of the spring-type or high-frequency relay is within 100 microseconds, which meets the fast switching requirements of this invention.

[0101] Example 4

[0102] According to a specific embodiment of the present invention, the SiC MOSFET threshold voltage monitoring method of the present invention will be described in detail.

[0103] This invention provides a method for monitoring the threshold voltage of a SiC MOSFET, employing any of the aforementioned SiC MOSFET threshold voltage monitoring systems, and includes the following steps:

[0104] Step 101: At the first preset time point t1, the controller controls the drive module to output a high-level signal VP0 of the preprocessing pulse. The pulse width of the preprocessing pulse is t_con. The high-level signal VP0 of the preprocessing pulse is applied to the gate of the SiC MOSFET of the sample under test.

[0105] Step 102, at the second preset time point t2, t2=t1+t_con, the controller controls the drive module to output a high-level signal VP1 of the test pulse, the relay of the first switch K1 is energized, the relay coil of the third switch K3 is energized, and the relay of the second switch K2 is energized after the interval time t_float, t2+t_float=t3;

[0106] Step 103: At time point t3, the relay of the second switch K2 is energized, which energizes the relay coil of the fourth switch K4 to detect the threshold voltage.

[0107] The duration of t_con is controlled by the controller, which in turn controls the pulse width t_VT of the test pulse.

[0108] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A SiC MOSFET threshold voltage monitoring system, characterized in that, include: Controller, switch module, drive module, test circuit, threshold voltage acquisition module, and power supply module; The power supply module provides power to the controller, the switch module, and the drive module; The controller is connected to the drive module and the switch module respectively; the drive module is connected to the switch module; the switch module is connected to the test circuit; the test circuit is connected to the threshold voltage acquisition module. The controller controls the drive module, which in turn activates the switch module. The activation of the switch module causes the test circuit to switch between the test pulse preprocessing circuit and the threshold voltage detection circuit. The activation of the switch module is completed within 100 microseconds. The switch module includes multiple spring relays or multiple high-frequency relays. The activation time of the spring relays or high-frequency relays is within 100 microseconds. The switch module controls the first switch K1, the second switch K2, the third switch K3, and the fourth switch K4, which are all switches of the relays in the switch module. When the test circuit is a threshold voltage detection circuit, the threshold voltage acquisition module acquires the threshold voltage of the test circuit; The test pulse preprocessing circuit applies a preprocessing pulse before the test pulse and sets an interval time between the preprocessing pulse and the test pulse; The test circuit includes the SiC MOSFET under test and peripheral circuits. When the first switch K1 and the second switch K2 are closed and the third switch K3 and the fourth switch K4 are open, the test circuit is the test pulse preprocessing circuit. When the first switch K1 and the second switch K2 are open and the third switch K3 and the fourth switch K4 are closed, the test circuit is the threshold voltage detection circuit; The first terminal of the first switch K1 is connected to the first terminal of the third switch K3 and the gate of the SiCMosfet under test; the second terminal of the third switch K3 is connected to the first terminal of the second switch K2, the first terminal of the fourth switch K4 and the drain of the SiCMosfet under test; the second terminal of the second switch K2 is connected to the source of the SiCMosfet under test and then grounded; the second terminal of the fourth switch K4 is connected to the positive terminal of the constant current source, and the negative terminal of the constant current source is grounded. The switching module further includes a first resistor, a first capacitor, a second resistor, and a first transistor. The first resistor is connected to the base of the first transistor. When the test circuit is the threshold voltage detection circuit, the test pulse is input to the base of the first transistor through the first resistor. The collector of the first transistor is connected to the coil of the first switch K1 and the coil of the second switch K2, respectively. The collector of the first transistor is also connected to the second resistor. The second resistor and the first capacitor are connected in series and then in parallel with the coil of the second switch K2.

2. The SiC MOSFET threshold voltage monitoring system according to claim 1, characterized in that, The width t_con of the preprocessing pulse is 1-100 ms.

3. The SiC MOSFET threshold voltage monitoring system according to claim 1, characterized in that, The interval t_float set between the preprocessing pulse and the test pulse is <10 ms.

4. The SiC MOSFET threshold voltage monitoring system according to claim 1, characterized in that, The width of the test pulse is t_VT < 10 ms.

5. A method for monitoring the threshold voltage of a SiC MOSFET, characterized in that, The SiC MOSFET threshold voltage monitoring system according to any one of claims 1-4 includes the following steps: Step 101: At the first preset time point t1, the controller controls the drive module to output a high-level signal VP0 of the preprocessing pulse. The pulse width of the preprocessing pulse is t_con. The high-level signal VP0 of the preprocessing pulse is applied to the gate of the SiC MOSFET of the sample under test. Step 102, at the second preset time point t2, t2=t1+t_con, the controller controls the drive module to output a high-level signal VP1 of the test pulse, the relay of the first switch K1 is energized, the relay coil of the second switch K2 is energized, and the relay of the third switch K3 is energized after the interval time t_float, t2+t_float=t3; Step 103: At time point t3, the relay of the third switch K3 is energized, which energizes the relay coil of the fourth switch K4 to detect the threshold voltage.

6. The SiC MOSFET threshold voltage monitoring method according to claim 5, characterized in that, The duration of t_con is controlled by the controller, which in turn controls the pulse width t_VT of the test pulse.

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