Online Junction Temperature Monitoring Method for SiC MOSFETs Based on Turn-Off Miller Plateau Voltage

Online junction temperature monitoring of SiC mosfet based on turn- off Miller plateau voltage ( V _MP,off ) has been explored in this article. As the junction temperature rises, V _MP,off experiences a decline while extending its duration, thereby enhancing the precision of sampling V _MP,off with a diminutive turn- off resistance ( R_{g ,off} ). A novel extraction approach for V _MP,off is introduced, involving the continuous sampling of gate voltage via a network of resistances and an analog-to-digital converter (ADC). V _MP,off is ascertained through the discrepancy between two consecutive output points of the ADC. Validation of this monitoring technique is conducted through double pulse tests and a buck converter under varying temperatures. Empirical findings demonstrate a commendable linear relationship between V _MP,off and junction temperature. In the quest for a balance among thermal sensitivity accuracy, turn- off delay, and turn- off loss, a recommended value for R_{g ,off} of SCT3040KR stands at approximately 15 Ω. Employing a 15 Ω R_{g ,off} , the temperature sensitivity of V _MP,off for SCT3040KR and SCT3105KR hovers around −11.3 mV/°C and −9.1 mV/°C, respectively. With calibrations of aging and threshold voltages in advance, the proposed methodology exhibits promising potential in the realm of SiC mosfet junction temperature monitoring.