Closed Loop dv/dt Control for Equal Voltage Sharing Between Series Connected SiC MOSFETs

Abstract

Series-connected Low Voltage (LV) devices (SiC MOSFETs) is an efficient and cost-effective approach to realize Medium Voltage (MV) power switch for many emerging MV power conversion applications. This approach has low on-state resistance, which results in low conduction losses and it is more cost-effective than equivalent MV semiconductor devices. The main concern of the series connected SiC devices is unequal voltage distribution during commutation especially turn-off period. This paper proposes a closed loop active gate driver circuit which can control the rate of rise of the drain-source voltage of SiC MOSFET during turn-off and turn-on interval. The principle of operation for the active gate driver circuit is explained and based on the derived model for the control circuit, stability analysis of the closed-loop system is carried out for SiC MOSFET. Simulations were carried out using SaberRD tool and finally experimental results obtained to verify the effectiveness of the proposed technique.