Modeling, Design, and Evaluation of Active $\mathrm{\text{} d }v/\mathrm{\text{} d }t$ Balancing for Series-Connected SiC MOSFETs

Series connection of SiC
MOSFET
s provides an effective alternative to achieving higher blocking voltage with simpler circuit topologies. However, the voltage imbalance during the switching transient remains a critical issue. Recently, an active
$\mathrm{\text{} d }v/\mathrm{\text{} d }t$
control approach utilizing a controllable equivalent Miller capacitor has been proved to be an effective, low-loss, and compact solution. This article renders an improved control circuit with comprehensive modeling and analysis. First, the original circuit is modified with an additional bipolar-junction-transistor and pulsed control signal so that the external capacitor can be fully reset every switching cycle. Second, a simplified model of the active
$\mathrm{\text{} d }v/\mathrm{\text{} d }t$
control is derived to unveil the linear correlation between the control voltage and the device
$\mathrm{\text{} d }v/\mathrm{\text{} d }t$
during the turn-
off
transient. Third, a feedback control model is described by difference equations for stability analysis, offering parameter selection guidelines for the control process. Fourth, experimental results with two series-connected SiC
MOSFET
s under 1.5-kV dc-link voltage are demonstrated to validate the open-loop control model and closed-loop stability. Finally, the control method is expanded to eight series-connected devices under 6 kV to prove its scalability and potential for medium-voltage high-current applications.