Analysis and Flexible DV/DT Control of an Active Clamping Topology for Series-Connected SiC MOSFETs

Series-connection of SiCmosfets is an attractive solution to build cost effective and high efficiency medium voltage converters, however, the unequal voltage sharing among the power devices and the induced highdv/dtproblems should be considered carefully. In this article, an active clamping topology and correspondingdv/dtcontrol method for series-connected SiCmosfets are proposed. With the proposed topology, the drain-source voltage of each SiCmosfetcan be clamped by discrete clamping capacitor, resulting in high robust switching. Besides, the clamping capacitor voltages can be autobalanced during the topology operation, so the peak voltages of the series-connected SiCmosfets can be easily balanced. By simply adjusting the gate drive delay time, the proposed topology could reduce the equivalentdv/dtof the device string with very small increase in power loss, so the highdv/dtinduced switching noise can be suppressed greatly. Finally, a 4.8 kV/10 A half-bridge prototype is established with six SiCmosfets connected in series within per bridge arm, experimental results are provided to show the effectiveness and advancement of the proposed method.