Characterization and Optimization of SiC Freewheeling Diode for Switching Losses Minimization Over Wide Temperature Range

Inhalt:
This paper presents the dynamic characterization of SiC MOSFET body diode and Schottky diode with loss and charge comparison of different freewheeling device implementations under different temperatures. A pulse tester is designed to obtain loss and charge measurements accurately. Turn-on waveforms are measured and compared under different temperatures with different freewheeling device implementations. Turn-on loss and charge measurement results are calculated based on turn-on voltage and current. Measurement. The results indicate that even for SiC MOSFETs, using only the body diode as a freewheeling diode still have significant reverse recovery charge, especially for high temperature conditions. Therefore, turn-on loss increases significantly under high temperature. Adding antiparallel SiC schottky diode can eliminate reverse recovery charge and keep switching loss temperature independent. However, the output capacitance will increase total capacitive charge and may increase the turn-on loss under low temperature. Based on the testing results, a design guideline is presented for freewheeling diode selection for SiC MOSFET operation under different applications.