A High-Sensitivity Online Junction Temperature Monitoring Method for SiC mosfets Based on the Turn-on Drain–Source Current Overshoot

Junction temperature monitoring is the basis of high reliability operation for silicon carbide (SiC) devices, since thermal stress is the dominating aging factor. Conventional thermal sensitive electrical parameter methods have a poor monitoring performance for SiC <sc>Mosfets</sc> with low sensitivity. Thus, a high-sensitivity online junction temperature monitoring method is proposed based on the turn-<sc>on</sc> drain–source current overshoot. First, theoretical analysis is provided to clarify that the temperature difference between the body diode region and the on-state resistance region can be ignored in SiC <sc>Mosfets</sc>. It is an important basis for the proposed method, which is proven by an isothermal experiment. It is the first time to discover that the turn-<sc>on</sc> current overshoot (Δ<italic>i<sub>Cm</sub></italic>) of SiC <sc>Mosfets</sc> consists of both the reverse recovery current (<italic>i</italic><sub>RR</sub>) and the intrinsic current overshoot (Δ<italic>i</italic><sub>0</sub><italic><sub>m</sub></italic>). Next, a novel <italic>T<sub>j</sub></italic> monitoring strategy for SiC <sc>Mosfets</sc> is proposed based on comprehensive utilization of <italic>i</italic><sub>RR</sub><italic><sub>m</sub></italic>, Δ<italic>i</italic><sub>0</sub><italic><sub>m</sub></italic> and Δ<italic>i<sub>Cm</sub></italic>. Finally, the effectiveness of the proposed method is verified by online experiments based on a dc–dc converter. The proposed method is more accurate than conventional TSEP methods with a high sensitivity of 20 mA/°C. Moreover, it still has a high monitoring performance when boundary conditions change.