A sic mosfet junction temperature acquisition circuit and method

Abstract

The application discloses a kind of SIC MOSFET junction temperature acquisition circuit and method, the circuit includes heating current source, heating switch, junction temperature measurement unit, inductive current source and inductive current bypass unit, heating current source and heating switch are connected in series to the one end of junction temperature measurement unit, the other end of junction temperature measurement unit, inductive current source and inductive current bypass unit are connected in turn;Heating switch opens, heating current source applies test current to junction temperature measurement unit by heating switch, at this time, the current of inductive current source flows in inductive current bypass unit, after reaching prediction time, disconnect heating switch, heating current source stops working, inductive current bypass unit is closed, and the current of inductive current source flows through the body diode of measured piece in junction temperature measurement unit;The application has the advantages that SIC MOSFET junction temperature measurement error is greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of SIC MOSFET power cycle test, more particularly to a SIC MOSFET junction temperature acquisition circuit and method. BACKGROUND

[0002] Compared with SIIGBT devices, SIC MOSFET has lower conduction loss, higher switching frequency and higher breakdown field strength, resulting in wide application of SIC MOSFET in electric vehicle drive, photovoltaic inverter, switching power supply and aerospace field in recent years. In order to ensure the reliability of the device, the service life of the device needs to be evaluated before being put into practical application. Among them, power cycle experiment (referring to international standard IEC-60747-9:2019) is an important index for evaluating the service life of SIC MOSFET device. Since SIC MOSFET device often works in high voltage and large current field, its junction temperature will be very high. According to Arrhenius law, the service life of the device will be halved for every 10℃ increase in temperature. Therefore, for IC MOSFET device life evaluation, the acquisition of junction temperature is a key step.

[0003] The traditional junction temperature acquisition method is to calculate the junction temperature of the device by the voltage drop generated by the sensing current (usually one thousandth of the working current) in the body diode at the moment of heating current disconnection and the relationship curve between the junction temperature fitted before the experiment and the on-voltage drop of the body diode. For example, the SiC MOSFET device junction temperature measurement method, device and medium disclosed in Chinese patent publication No. CN113933676A. Due to the material of SIC MOSFET, the SIC MOSFET band gap is much higher than that of SI, and the SIC / SIO2 interface trap, so the sensing current needs to fill the interface trap first, and then the voltage drop of the body diode slowly rises, and finally tends to be stable, so the steady-state voltage drop generated by the sensing current on the body diode takes a long time, resulting in a large error in the junction temperature measurement. SUMMARY

[0004] The technical problem to be solved by the present application is that the existing SIC MOSFET junction temperature measurement has a large error.

[0005] The present application solves the above technical problems by the following technical means: a SIC MOSFET junction temperature acquisition circuit, comprising a heating current source, a heating switch, a junction temperature measurement unit, a sensing current source and a sensing current bypass unit, the heating current source and the heating switch are connected in series and then connected to one end of the junction temperature measurement unit, the other end of the junction temperature measurement unit, the sensing current source and the sensing current bypass unit are connected in sequence.

[0006] The heating switch is opened, the heating current source applies a test current to the junction temperature measuring unit through the heating switch, the measured element in the junction temperature measuring unit generates heat under the action of the test current, at this time, the current of the induction current source flows in the induction current bypass unit, after the predicted time, the heating switch is turned off, the heating current source stops working, the induction current bypass unit is closed, and the current of the induction current source flows through the body diode of the measured element in the junction temperature measuring unit, at this time, the voltage change of the body diode of the measured element is measured, when the voltage is stable, the junction temperature is obtained according to the relationship between the voltage and the junction temperature.

[0007] The measured element in the heating current off moment, the induction current is switched from the induction current bypass unit to the junction temperature measuring unit, the induction current source which is always in working state is rapidly applied to the measured device, the steady-state voltage drop between the body diode of the measured element is rapidly established, the time for establishing the steady-state voltage is greatly shortened, the voltage value obtained at this time is more accurate when converted into temperature, and thus the SIC MOSFET junction temperature measurement error is greatly reduced.

[0008] Further, the heating switch is a triode, the positive electrode of the heating current source is connected with the collector of the triode, and the negative electrode of the heating current source and the emitter of the triode are connected with the junction temperature measuring unit.

[0009] Further, the junction temperature measuring unit comprises a measured element and a MOS tube Q1, the measured element is a MOS tube, the source of the measured element is connected with the negative electrode of the heating current source and the source of the MOS tube Q1, the drain of the measured element is connected with the emitter of the triode and the negative electrode of the induction current source, and the drain of the MOS tube Q1 is connected with the positive electrode of the induction current source.

[0010] Further, the measured element is a SIC MOSFET, and the MOS tube Q1 is a SI MOSFET.

[0011] Further, the current of the induction current source is one thousandth of the working current of the heating current source.

[0012] Further, the induction current bypass unit comprises a MOS tube Q2 and a MOS tube Q3, the drain of the MOS tube Q2 is connected with the positive electrode of the induction current source, the source of the MOS tube Q2 is connected with the source of the MOS tube Q3, and the drain of the MOS tube Q3 is connected with the negative electrode of the induction current source.

[0013] Further, the MOS tube Q2 is a SI MOSFET, and the MOS tube Q3 is a SIC MOSFET.

[0014] The application further provides a method for obtaining a SIC MOSFET junction temperature, and the method comprises the following steps:

[0015] The heating switch is opened, and the current of the heating current source flows through the channel of the measured piece, the measured piece is in an open state, the MOS tube Q1 is in a closed state, the MOS tube Q2 is open, and the MOS tube Q3 is always in a closed state, at this time, the induction current of the induction current source flows through the MOS tube Q2 channel and the body diode of the MOS tube Q3; when the heating switch is disconnected, the heating current source is in an off state, at this time, the measured piece is also in an off state, the MOS tube Q1 is open, the MOS tube Q2 is closed, and the MOS tube Q3 is always in a closed state, at this time, the induction current of the induction current source flows through the MOS tube Q1 channel and the body diode of the measured piece.

[0016] Further, the preset time is 4-10s.

[0017] Further, the size of the test current is 20A-40A.

[0018] The application has the advantages that:

[0019] (1) In the application, the induction current is switched from the induction current bypass unit to the junction temperature measurement unit at the heating current off time, the induction current source which is always in a working state is rapidly applied to the measured device, the steady-state voltage drop across the body diode of the measured device is rapidly established, the time for establishing the steady-state voltage is greatly shortened, the voltage value obtained at this time is more accurate when converted into temperature, and the SIC MOSFET junction temperature measurement error is greatly reduced.

[0020] (2) In the application, the induction current passes through the body diode of the MOS tube Q3 in the induction current bypass unit, and also passes through the body diode of the measured device when switched to the junction temperature measurement unit, at this time, the steady-state voltage drop across the body diode of the measured device is rapidly established, and the time for establishing the steady-state voltage is greatly shortened.

[0021] (3) In the traditional junction temperature measurement circuit, a plurality of diodes are connected in series in the measurement loop, there is a risk of large current flowing into the induction current source during the large current heating stage and at the end of the life of the measured device, the series connection of the diodes also prolongs the time for the body diode of the measured device to reach the steady-state voltage, and causes measurement error, while in the application, the induction current source adopts a MOS tube active switching mode, the MOS tube Q1 is in a closed state during the heating current working stage, the heating current cannot flow through the induction current source, there is no risk of reverse flow of the heating current, and the induction current source will not be burned out, and the circuit is safer and more reliable. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A principle diagram of a SIC MOSFET junction temperature acquisition circuit provided by the embodiment of the application;

[0023] Figure 2A comparison curve diagram of voltage results obtained by the technical method and the traditional junction temperature measurement method in the method for obtaining a junction temperature of a SIC MOSFET circuit provided by the embodiment of the present application under a heating current of 20A working condition;

[0024] Figure 3 A comparison curve diagram of voltage results obtained by the technical method and the traditional junction temperature measurement method in the method for obtaining a junction temperature of a SIC MOSFET circuit provided by the embodiment of the present application under a heating current of 40A working condition. DETAILED DESCRIPTION

[0025] To make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0026] As shown in Figure 1 , the embodiment of the present application provides a SIC MOSFET junction temperature acquisition circuit, which comprises a heating current source 1, a heating switch 2, a junction temperature measurement unit 3, an induced current source 4 and an induced current bypass unit 5. The heating current source 1 and the heating switch 2 are connected in series and then connected to one end of the junction temperature measurement unit 3. The other end of the junction temperature measurement unit 3, the induced current source 4 and the induced current bypass unit 5 are connected in sequence. It should be noted that the heating current source 1 is only a common current source, which does not have heating performance itself. When the heating current source 1 is connected to the junction temperature measurement unit 3 and applies a current to the junction temperature measurement unit 3, the heating current source 1 will cause the DUT (device under test) in the junction temperature measurement unit 3 to heat, and thus the heating current source 1 is called. The heating switch 2 is connected to the heating current source, and the heating switch 2 applies a test current to the junction temperature measurement unit 3 to make the DUT heat, and thus the heating switch 2 is called. Similarly, the induced current source 4 is also only a common current source, which emits a current whose size is one thousandth of the working current of the heating current source 1, and the current is called induced current.

[0027] Referring to Figure 1 , the heating switch 2 is a triode, the positive electrode of the heating current source 1 is connected to the collector of the triode, and the negative electrode of the heating current source 1 and the emitter of the triode are connected to the junction temperature measurement unit 3.

[0028] Referring to Figure 1The junction temperature measuring unit 3 comprises a measured piece DUT and a MOS tube Q1, the measured piece DUT is a SIC MOSFET, and the MOS tube Q1 is a SI MOSFET. The source of the measured piece DUT is connected with the negative pole of the heating current source 1 and the source of the MOS tube Q1, the drain of the measured piece DUT is connected with the emitter of the triode and the negative pole of the induced current source 4, and the drain of the MOS tube Q1 is connected with the positive pole of the induced current source 4.

[0029] Continuing to refer to Figure 1 The induced current bypass unit 5 comprises a MOS tube Q2 and a MOS tube Q3, the MOS tube Q2 is a SI MOSFET, and the MOS tube Q3 is a SIC MOSFET. The drain of the MOS tube Q2 is connected with the positive pole of the induced current source 4, the source of the MOS tube Q2 is connected with the source of the MOS tube Q3, and the drain of the MOS tube Q3 is connected with the negative pole of the induced current source 4.

[0030] The working principle of the present application is as follows: the heating switch 2 is opened, and the current of the heating current source 1 flows through the channel of the measured piece DUT, so that the measured piece DUT is in an open state. The measured piece DUT will appear junction temperature under the action of the test current, and in practical application, the junction temperature of the measured piece DUT can reach the preset temperature range by controlling the test current to be applied for a preset time and controlling the size of the test current. The measured piece DUT is in an open state, the MOS tube Q1 is in a closed state, the MOS tube Q2 is open, and the MOS tube Q3 is always in a closed state. At this time, the induced current of the induced current source 4 flows through the MOS tube Q2 channel and the body diode of the MOS tube Q3. When the heating switch 2 is turned off, the heating current source 1 is in an off state, at this time, the measured piece DUT is also in an off state, the MOS tube Q1 is open, the MOS tube Q2 is closed, and the MOS tube Q3 is always in a closed state. At this time, the induced current of the induced current source 4 flows through the MOS tube Q1 channel and the body diode of the measured piece DUT. At this time, the voltage change of the body diode of the measured piece DUT is measured, and when the voltage is stable, the junction temperature is obtained according to the relationship between the voltage and the junction temperature. The induced current will pass through the body diode of the MOS tube Q3 in the induced current bypass unit 5, and also pass through the body diode of the measured piece DUT when switching to the junction temperature measuring unit 3. At this time, the steady-state voltage drop across the body diode of the measured piece DUT will be quickly established, greatly shortening the time for establishing the steady-state voltage. At this time, the voltage value obtained for calculating the temperature will be more accurate. The relationship between the voltage of the body of the measured piece DUT and the temperature is the prior art, and will not be described here. The preset time is 4-10s. The size of the test current is 20A-40A.

[0031] Figure 2 and Figure 3The voltage comparison curve graphs of the heating current source 1 under the conditions of 20A and 40A heating current are obtained by using the technical method and the traditional junction temperature measurement method respectively, and the curve shows that the steady-state voltage of the body diode reaches the steady-state voltage value more quickly by using the technical method, thereby better realizing the acquisition of the SIC MOSFET junction temperature.

[0032] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A SIC MOSFET junction temperature acquisition circuit, characterized by, The heating current source, the heating switch, the junction temperature measuring unit, the induced current source and the induced current bypass unit are connected in sequence. The heating switch is opened, and the heating current source applies a test current to the junction temperature measuring unit through the heating switch. The measured component in the junction temperature measuring unit generates heat under the action of the test current. At this time, the current of the induced current source flows in the induced current bypass unit and reaches a preset time. Then, the heating switch is turned off, the heating current source stops working, the induced current bypass unit is closed, and the current of the induced current source flows through the body diode of the measured component. At this time, the voltage change of the body diode of the measured component is measured. When the voltage is stable, the junction temperature is obtained according to the relationship between the voltage and the junction temperature.

2. The SIC MOSFET junction temperature acquisition circuit according to claim 1, characterized by, The heating switch is a triode, the positive electrode of the heating current source is connected with the collector of the triode, and the negative electrode of the heating current source and the emitter of the triode are connected with the junction temperature measuring unit.

3. The SIC MOSFET junction temperature acquisition circuit of claim 2, wherein, The junction temperature measuring unit includes a measured component and a MOS tube Q1. The measured component is a MOS tube, the source of the measured component is connected with the negative electrode of the heating current source and the source of the MOS tube Q1, the drain of the measured component is connected with the emitter of the triode and the negative electrode of the induced current source, and the drain of the MOS tube Q1 is connected with the positive electrode of the induced current source.

4. The SIC MOSFET junction temperature acquisition circuit of claim 3, wherein, The measured component is a SIC MOSFET, and the MOS tube Q1 is a SIMOSFET.

5. The SIC MOSFET junction temperature acquisition circuit of claim 3, wherein, The current of the induced current source is one thousandth of the working current of the heating current source.

6. The SIC MOSFET junction temperature acquisition circuit of claim 3, wherein, The induced current bypass unit includes a MOS tube Q2 and a MOS tube Q3. The drain of the MOS tube Q2 is connected with the positive electrode of the induced current source, the source of the MOS tube Q2 is connected with the source of the MOS tube Q3, and the drain of the MOS tube Q3 is connected with the negative electrode of the induced current source.

7. The SIC MOSFET junction temperature acquisition circuit of claim 6, wherein, The MOS tube Q2 is a SIMOSFET, and the MOS tube Q3 is a SIC MOSFET.

8. The method of claim 6-7, wherein, The method includes: When the heating switch is opened, the measured component is in an open state, the MOS tube Q1 is in a closed state, the MOS tube Q2 is open, and the MOS tube Q3 is always in a closed state. At this time, the induced current of the induced current source flows through the channel of the MOS tube Q2 and the body diode of the MOS tube Q3. When the heating switch is turned off, the heating current source is in an off state. At this time, the measured component is also in an off state, the MOS tube Q1 is open, the MOS tube Q2 is closed, and the MOS tube Q3 is always in a closed state. At this time, the induced current of the induced current source flows through the channel of the MOS tube Q1 and the body diode of the measured component.

9. The method of claim 8, wherein, The preset time is 4-10s.

10. The method of claim 8, wherein, The size of the test current is 20A-40A.

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