Online Junction-Temperature Sensing of SiC MOSFETs with Minimal Calibration Effort

This work proposes a junction-temperature sensing method for silicon-carbide (SiC) MOSFETs with minimal calibration effort. The method utilizes the time delay between the gate-voltage and the device-current rise as a temperature-sensitive electrical parameter (TSEP) that exhibits two unique features: The time delay depends linearly on the junction temperature and shows nearly no sensitivity to the device current. Both features combined yield junction-temperature sensing with minimized calibration effort that is crucial for practical applications. Furthermore, this work demonstrates that the specific temperature dependence of the charge carrier mobility of SiC devices renders the sensing method particularly suitable for the application on SiC MOSFETs. This paper first defines the considered TSEP and describes the corresponding junction-temperature sensing method. Subsequently, a sensitivity analysis is performed to identify the influences on the considered time delay and to analyze the differences in the behavior of the TSEP for Si and SiC devices. Lastly, the method is validated by measurements on an SiC power module.