A Current Distribution Mechanism Study Between an SiC MOSFET Body Diode and a Paralleled SiC Schottky Barrier Diode During Freewheeling

Paralleling an external SiC Schottky barrier diode (SBD) with an SiC MOSFET redistributes the reverse-conduction current and may reduce the reverse-recovery energy. However, the benefit depends on device selection and operating conditions, and an unsuitable SBD can increase the reverse-recovery energy. This paper presents simplified interval-specific models for turn-on, forward conduction, and turn-off and evaluates their qualitative trends using double-pulse tests. For the tested devices and operating conditions, the observed turn-on current distribution is qualitatively consistent with the combined influence of capacitive displacement currents and branch parasitic impedance. The forward-conduction waveforms exhibit case-temperature-dependent RL-type current redistribution. Compared with the configuration without an external SBD, the best-performing SBD group reduces the mean reverse-recovery energy Err by 19.8–54.5% at Tc=25 °C and by 70.0–81.4% at Tc=175 °C across four voltage–current operating points. Other SBD selections increase Err at low case temperature. Reducing the dead time from 3 μs to 500 ns increases the peak magnitude of the total reverse current by 36.8%. These results provide design considerations for the tested devices and operating range.