An Active Voltage Balancing Method for Series Connection of SiC MOSFETs With Coupling Inductor

The series connection of SiC MOSFETs is an attractive way to expand the voltage of SiC devices. However, the voltage imbalance is among the most critical challenges to overcome. In this letter, an active voltage balancing method suitable for two devices connected in series is proposed. Specifically, a multiwinding coupling inductor with low number of turns is applied to achieve voltage deviation sampling and high-quality signal isolation. The sampled signal is further conditioned by a controlled current source and injected into the gate-source voltage. Owing to the high output impedance of the current source, the voltage balancing circuit is independent of the normal switching of SiC MOSFETs under balanced conditions. The operation principle, parameter design, and implementation are given in detail.