Turn-off Analysis and Modeling of Releasing Loss in Snubber Capacitor Self-Balancing Circuits for Series-Connected SiC MOSFETs Applied to High-Voltage Pulsed Power Systems

SiC MOSFETs demonstrate superior characteristics such as high switching speed and high breakdown voltage, the development of series-connected SiC MOSFETs-based pulse power switches has emerged as a primary research truth. To meet the dynamic voltage balancing demands of series-connected SiC MOSFETs under ultra-fast switching conditions, the snubber capacitor self-balancing circuit provides advantages including simplicity, high reliability, and full-speed switching capability. However, the absence of quantitative analysis on releasing loss in this topology limits circuit design and optimization. Meanwhile, the modeling of the series-connected SiC MOSFETs turn-off process under ohmic loads is understudied, which increases the difficulty of loss modeling. This paper investigates the working principles and turn-off process of the topology, simplifies the model under ohmic load conditions, and proposes a method for analyzing the drain-source voltage rise rate of series-connected SiC MOSFETs under different delay combinations while establishing a releaseing loss model. Moreover, this method is scalable for extending the number of series-connected devices. The trends demonstrated by the model is verified by comparison of multiple simulation results.