Voltage Balancing of Series Connected SiC MOSFETs with Adaptive-impedance Self-powered Gate Drivers

Passive clamping snubbers for voltage balancing (VB) series-connected power devices exhibit strong applicability and high robustness; moreover, they are particularly suitable for the emerging fast-switching silicon-carbide (SiC) metal-oxide-semiconductor field-effect transistors (mosfets). However, the compromise still exists as a better VB performance comes at a penalty of a larger loss of snubber. Consequently, in this article, novel adaptive-impedance 'snubbers' are proposed for series-connected SiC mosfets on the basis of converter-based self-powered gate driver design, and a better tradeoff is achieved between loss and VB both in static and dynamic states. Further, the proposed passive VB strategy could be combined with an active delay control strategy by introducing an extra closed-loop controller. Benefiting from a more accurately established small-signal system model, the closed-loop numerical parameters are easier to design. As a result, well-balanced voltage distribution is realized during the continuously switching process of series-connected SiC mosfets. To verify the effectiveness, a comprehensive analysis is first provided as guidance, followed by the corresponding detailed hardware and software design. Finally, the experiments are conducted by using two SiC mosfets, which show excellent VB performance at a 110 kV/μs switching speed.