Current Sharing Behavior of Parallel Connected Silicon Carbide MOSFETs Influenced by Parasitic Inductance

The parasitic inductance from the wirings and the terminals of SiC MOSFETs has a significant impact on the behavior of current sharing of parallel-connected SiC MOSFETs. To investigate the mechanism of current mismatch in response to the parasitic inductance, the circuit model of parallel-connected SiC MOSFETs is built to obtain the mathematic relationship between current difference and parasitic inductance in both dynamic and static states. Because the way of connecting the parallel-connected SiC MOSFETs with the coupled inductor in series can lead to the turn-off voltage ringing and overshoot, an improved structure is further proposed in this paper. A RCD snubber circuit is added into the proposed structure by referring to the coupled inductor with transformer in fly-back converter. Finally, the approach is verified through the LTspice software and experiments.