Digital control based voltage balancing for series connected SiC MOSFETs under switching operations

Recently, with research and development of SiC power devices, 1.2 kV SiC MOSFETs have become commercially available. The parasitic parameters, such as output capacitance, in each power device are not identical, because they depend on the device structure and material properties. Therefore, voltage sharing of turn-off operations under series-connection conditions of the power devices may be affected. This paper proposes a voltage balancing method for series-connected SiC MOSFETs under turn-off operations using digital control circuits. To compensate for the voltage unbalance conditions, a time-delay control for the gate drive circuit using a digital delay line is employed; experimental results using a buck chopper circuit using SiC MOSFETs and Schottky barrier diodes rated at 1.2 kV are also presented.