A Coupled Inductor Based Circuit for Voltage Balancing among Series Connected SiC MOSFETs

The voltage unbalance among the devices remains one of the critical challenges to connect the devices in series in medium voltage, high power applications. In this paper, a coupled inductor based RC snubber circuit is proposed to balance the voltages among the series connected SiC MOSFETs. The coupled inductors are applied as a gate drive signal amplitude compensation method to achieve high response speed. In conjunction with the widely adopted RC snubbers in voltage balancing technique, the coupled inductors are added to transfer the current deviation from the devices into a compensated gate source voltage. As a result, the voltage is actively balanced by simply using the passive components. Compared with the traditional RC snubber circuit, the proposed method realizes fine voltage adjustment so as to reduce the negative effect caused by parallel capacitors. Moreover, the proposed method only needs a coupled inductor with RC snubber circuit which is simple to realize. The operation principle of the coupled inductor is discussed and verified through experiments.