Package Degradation’s Impact on SiC MOSFETs Loss: A Comparison of Kelvin and Non-Kelvin Designs

Aging-related electrical parameter shifts in SiC MOSFETs can adversely affect the power converter performance. In this paper, the package degradation’s effect on the device’s switching loss is comprehensively investigated. Both the TO-packaged 3-pin and 4-pin devices are evaluated, and the device’s on-resistances and switching losses are compared before and after the package degradation. From the experimental results, it is observed that the wire bond degradation can significantly affect the switching loss of the 3-pin devices: more than 23.8% / 27% turn-on/off loss increase is observed, and it becomes more noticeable at higher current and faster switching conditions. The increased package resistance and electrical coupling to the gate loop contribute to the loss variation. In contrast, the switching loss in the 4-pin Kelvin connected SiC MOSFET is not affected by package degradation as the Kelvin-source connection helps to decouple the package degradation’s impact on gate drive circuits. The findings serve as a guideline for SiC MOSFETs based converter designs to ensure robust operation and avoid potential thermal instability issues in the long-term operation.