Design and Test of a 6 kV Phase-Leg using Four Stacked 1.7 kV SiC MOSFET High-Current Modules

The stacking or series-connection of Silicon Carbide (SiC) MOSFETs is an attractive solution for achieving higher blocking voltage using lower voltage power semiconductors in medium- and high-voltage converter applications. However, when connecting MOSFETs in series, device voltages can be unbalanced due to tolerance in device parameters, package and layout parasitic components, and gate-signal timing delays. A modular gate-driver design with active gate control is implemented in this work in order to balance voltages between series-connected devices. The design of an online 6 kV bus measurement board is also described in this paper. This work demonstrates balancing performance of four stacked high-current power modules totaling eight 1.7 kV SiC MOSFETs in series under 6 kV bus voltage using an active dv/dt balancing method. Switching losses are evaluated for both turn-on and turn-off transitions across all eight MOSFETs under a load current of 240 A.