Junction Temperature Correction Method for SiC MOSFET Based on Turn-Off Oscillation Frequency of Drain-Source Voltage

Turn-on change rate of drain current di $_{\text {DS(on)}}$ /dt is an electrical parameter suitable for online monitoring of junction temperature in SiC MOSFETs. In practical application, the change of the external circuit will change the temperature-sensitive characteristic of di $_{\text {DS(on)}}$ /dt. In this article, SiC MOSFET in Buck converter is taken as the research object. First, the influence of power loop inductance on di $_{\text {DS(on)}}$ /dt temperature sensitivity of SiC MOSFET is analyzed theoretically. Second, the relationship between the di $_{\text {DS(on)}}$ /dt of SiC MOSFET and the turn-off oscillation frequency of the drain-source voltage is established through the frequency spectrum of switching waveform with ringing. Based on theoretical and experimental studies, a method to modify the temperature-sensitive characteristic of di $_{\text {DS(on)}}$ /dt by turn-off oscillation frequency of drain-source voltage is proposed. The results show that the calibration method can largely eliminate the junction temperature monitoring error caused by the variation of the power loop inductance, and the maximum measurement error decreases from $100~^{\circ }$ C to $11.3~^{\circ }$ C after correction.