Preferred method of electrical parameter and measurement method, estimation method of si c mosfet gate oxide degradation

Abstract

The application provides a preferred method of electrical parameters and a measurement method, and an estimation method of SiC MOSFET gate oxide layer degradation, and the preferred method comprises the following steps: in combination with a gate oxide layer degradation model of SiC MOSFET and I-V characteristics of a turn-off process, a relationship model of several electrical parameters and a gate oxide layer degradation degree during the turn-off process is determined; in combination with the relationship model and actual working characteristics of a SiC inverter, several alternative electrical parameters are determined; based on an equivalent circuit model of each alternative electrical parameter, an online measurement difficulty of each alternative electrical parameter and a coupling degree with a SiC MOSFET temperature are evaluated, and a preferred electrical parameter is determined according to an evaluation result; and a mapping electrical parameter which is jointly measured with the preferred electrical parameter is determined. Through in-depth exploration of the relationship between gate oxide layer aging and each electrical parameter, the application can preferably select an electrical parameter suitable for online monitoring of the gate oxide layer degradation degree of SiC MOSFET.

Claims

1. A method for selecting preferred electrical parameters, characterized in that, Includes the following steps: Based on the gate oxide degradation model of SiC MOSFET and the IV characteristics of the turn-off process, a model is established to determine the relationship between several electrical parameters and the degree of gate oxide degradation of SiC MOSFET during the turn-off process. Based on the aforementioned relationship model and the actual operating characteristics of the SiC inverter, several candidate electrical parameters are determined. The actual operating characteristics of the SiC inverter include the drain-source voltage surge phenomenon caused by the turn-off process of each SiC MOSFET during its operation. The candidate electrical parameters are caused by parasitic parameters during the operation of the SiC inverter, and the parameter values ​​change with the degradation of the gate oxide layer of the SiC MOSFET. Based on the equivalent circuit model of each candidate electrical parameter, the difficulty of online measurement of each candidate electrical parameter and its coupling degree with the temperature of SiC MOSFET are evaluated, and the preferred electrical parameter is determined according to the evaluation results. The preferred electrical parameter is the surge voltage caused by the turn-off process of the SiC MOSFET itself. Determine the mapping electrical parameters to be measured in conjunction with the preferred electrical parameters, wherein the mapping electrical parameters are the stable drain-source current values ​​of the SiCMOSFET before it is turned off.

2. The preferred method for the electrical parameters according to claim 1, characterized in that, The relationship model is used to characterize at least the following electrical parameters and their gate oxide layer degradation during SiC MOSET turn-off: Miller voltage Drain-source voltage and its rate of change over time Drain source current and its rate of change over time .

3. The preferred method for the electrical parameters according to claim 1, characterized in that, The gate oxide degradation model of the SiC MOSFET is used to describe the internal structure, gate oxide degradation mechanism, and equivalent circuit of the SiC MOSFET.

4. The preferred method for the electrical parameters according to claim 1, characterized in that, For each SiC MOSFET in the upper arm, the plurality of alternative electrical parameters include the surge voltage caused by the turn-off process of the SiC MOSFET itself, and the surge voltage caused by the turn-off processes of the other two SiC MOSFETs in the same upper arm. For each SiC MOSFET in the lower arm, the plurality of alternative electrical parameters include the surge voltage caused by the turn-off process of the SiC MOSFET itself, and the surge voltage caused by the turn-off processes of the other two SiC MOSFETs in the same lower arm.

5. The preferred method for the electrical parameters according to claim 1, characterized in that, For each SiC MOSFET, the surge voltage caused by its own turn-off process, when superimposed on its drain-source voltage, has the highest amplitude on its drain-source voltage waveform.

6. The preferred method for the electrical parameters according to claim 1, characterized in that, For each SiC MOSFET, the magnitude of the surge voltage caused by its own turn-off process is related to the degree of degradation of its gate oxide layer, but not to its temperature.

7. The preferred method for the electrical parameters according to claim 1, characterized in that, For each SiC MOSFET, the magnitude of the surge voltage caused by its own turn-off process is related to the original parasitic parameters of the bridge arm in which it is located, and the original parasitic parameters of the bridge arm in which it is located are independent of its temperature.

8. A method for measuring electrical parameters, used for online measurement of the electrical parameters of a SiC MOSFET under test during the operation of a SiC inverter, characterized in that, The measured electrical parameter is linearly correlated with the preferred electrical parameter determined by the method described in claim 1.

9. The method for measuring electrical parameters according to claim 8, characterized in that, Includes the following operations: The online measurement of the electrical parameter under test is performed by connecting a measurement circuit during the operation of the SiC inverter, and the connection method of the measurement circuit is set so as not to introduce new parasitic parameters during the measurement of the electrical parameter under test.

10. A method for estimating the gate oxide degradation of a SiC MOSFET, characterized in that, Includes the following operations: Based on the results of online measurement of the measured electrical parameters and mapped electrical parameters of the SiC MOSFET under test during the operation of the SiC inverter, the degradation of the SiC MOSFET under test is estimated. The online measurement of the measured electrical parameters is performed by the measurement method of electrical parameters as described in claim 8.

11. The method for estimating the gate oxide degradation of a SiC MOSFET according to claim 10, characterized in that, The estimation of the degradation status of the tested SiC MOSFET includes: The gate oxide degradation of the tested SiC MOSFET is evaluated based on the deviation between the online measurement results of the tested electrical parameters and the mapped electrical parameters of the tested SiC MOSFET and the pre-established fitting curve of the preferred electrical parameters and the mapped electrical parameters of the same type and non-degraded SiC MOSFET.

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