An Junction Temperature Estimation Method in SiC MOSFET Modules Based on the Turn-off Delay Time and $v_{DS}$ Overshoot

An online junction temperature estimation method for silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) based on turn-off $v_{DS}$ peak voltage is proposed. First, the electrical behavior of SiC MOSFETs during turn-off is investigated and the temperature dependence of delay time and voltage overshoot during turn-off is discussed. The results show that the turn-off delay time is linearly and positively dependent on temperature, while the turn-off voltage overshoot has a low temperature dependence and both temperature-sensitive parameters are affected by the load current nonlinearity. Then, switching experiments under different conditions are performed to verify the temperature and load current dependence of the two parameters. Finally, based on the analysis of the experimental data, the mathematical relationships among the turn-off delay time, turn-off voltage overshoot, and junction temperature are established, and a novel junction temperature estimation model without the measurement of load current is obtained.