Body diode degradation study in EV SiC inverter topology under active/reactive loads

The aging behavior of the body diode in electric vehicle (EV) SiC inverters plays a critical role in system reliability. However, existing studies have not adequately analyzed the differential effects of active and reactive power cycling on its degradation mechanisms. To address this gap, this study establishes two experimental power cycling platforms to comparatively investigate the conduction characteristics and degradation patterns of the body diodes for SiC MOSFETs under different load conditions, revealing both theoretical influences and practical failure signatures. Experimental results demonstrate that under reactive power cycling, the body diode exhibits longer conduction periods than under active power cycling, exposing it to higher-frequency reverse recovery losses and thermal stress. However, due to the concurrent channel conduction path in MOSFETs during diode operation, current preferentially flows through the lower-resistance channel, thereby significantly reducing the effective conduction time of the body diode. This current-sharing mechanism results in negligible aging trends for both the forward voltage (V_F) and leakage current (I_DSS) across load types. These findings indicate no substantial body diode degradation under either active or reactive power cycling scenarios, providing new insights for reliability assessment in automotive SiC inverters by elucidating the actual current-path-dependent aging mechanisms.