Active Voltage Clamping of Series Connected 1.2kV SiC MOSFETs for Solid State Circuit Breaker Application

Abstract

SiC based Solid State Circuit Breakers (SSCBs) have recently entered into the market at the low voltage end of the network, and their adoption is slowly moving upstream as higher voltage offerings mature. Unavailability of commercial medium voltage SiC devices and their low current handling capability and high dv/dt hinder medium voltage SSCB designs. However, series connection of low voltage devices can meet the required voltage level if dynamic and static voltage balancing is possible. In this paper, an active voltage clamping method is proposed to achieve balanced dynamic turn-off voltage sharing between cascaded devices (CREE 1.2kV/30A SiC MOSFETs). Also, this method minimizes the number of components, overall switching losses and delay time by avoiding bulky and expensive RC snubbers. Different possible reasons behind dynamic voltage unbalancing and the proposed balancing technique have been verified in the LTspice simulation software. In addition, experimental results have been carried out to validate the effectiveness of the proposed technique.