Online Junction Temperature Measurement for SiC MOSFET Based on Dynamic Threshold Voltage Extraction

The online junction temperature monitoring of power devices is a viable technique to ensure the reliable operation of mission-critical power electronic converters. This article provides a potential approach for the junction temperature estimation of SiC MOSFETs based on the dynamic threshold voltage. The proposed method is independent of load current variation, which eliminates the complicated calibration procedure with load current. First, the physical mechanism and the temperature dependence of the dynamic threshold voltage are analyzed. An analytical model for the dynamic threshold voltage is built to investigate the effects of gate loop parameters on the temperature sensitivity and measurement accuracy. Then, the principle of the dynamic threshold voltage measurement circuit is introduced. Finally, the proposed dynamic threshold voltage measurement circuit is experimentally evaluated through the double-pulse tests. The experimental results show that the dynamic threshold voltage of SiC MOSFET has a good linear relationship with junction temperature. The temperature sensitivity of the dynamic threshold voltage of two SiC MOSFETs is approximately 5.2 mV/°C and 19.6 mV/°C, respectively.