A Modular Voltage Equalizing Driver for Series-Connected SiC MOSFETs

Voltage balance is critical for series-connected SiC MOSFETs in high-frequency and high-power applications. The voltage unbalance is induced by many factors, such as the devices parameter deviations, different voltage changing rates, asynchronous turn-on delay time and turn-off delay time, ect. This paper proposes a new modular voltage equalizing driver for series-connected SiC MOSFETs, which can not only provide driving signals to the MOSFETs but also realize voltage balance for series-connected SiC MOSFETs. A clamping capacitor is employed in the modular driver in order to realize the voltage balance of the series-connected SiC MOSFETs. Meanwhile, isolated bidirectional DC/DC converters are utilized to balance the clamping capacitor voltage by transferring the extra energies to the adjacent modular drivers. Moreover, the output voltage changing rates of the series-connected SiC MOSFETs can be controlled by turning on or turning off the SiC MOSFETs one by one. In addition, the modular structure of the proposed driver can improve the scalability of the system. The operation principles of the proposed modular voltage equalizing driver are analyzed in details. Finally, a simulation model is built in LTspice to verify the validity of the proposed modular voltage equalizing driver and the control strategies.