This paper investigates the current sink capacitor technique as a method to minimize the turn-off power losses of SiC MOSFETs operated with zero-voltage switching (ZVS). The method is simple and is based on adding auxiliary capacitors in parallel to the transistors, allowing the sink capacitor to take over part of the channel current, thus limiting the power loss while also advantageously lowering the dvds/dt ratio. The technique is validated and experimentally studied based on a single-pulse test setup with 1200 V-rated SiC MOSFETs, with several capacitances and gate resistance values, at various switched currents up to roughly 60 A. It is shown that by employing even very small capacitances, in the range of nanofarads, the turn-off power loss can be reduced by over tenfold, with a negligible impact on the volume and complexity of the system. Thus, the presented method can be effectively employed to improve soft-switched power converters.
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