Toward an In-Depth Understanding of the Commutation Processes in a SiC mosfet Switching Cell Including Parasitic Elements

This article provides in-depth insight into the commutation processes of high-speed SiC mosfets and investigates how they are influenced by various parasitic inductances. The switching dynamics of wide-bandgap power semiconductor devices are significantly larger compared to those of silicon devices. Therefore, the parasitic elements in the switching cell become increasingly important, as they limit the current and voltage slopes and cause oscillations. A thorough understanding of these effects is necessary for the design of highly efficient and integrated next-generation power electronic converters. However, the means of modeling hard-switched transitions, e.g., equivalent circuits, have not been adapted sufficiently compared to existing models on relatively slow-switching devices. This article presents the theory of commutation in high-speed semiconductor devices and outlines its key differences to traditional commutation models. These new insights are used to analyze the influence of parasitic inductances on the switching transitions. The theory is validated experimentally by double-pulse tests with variable parasitic inductances, performed on a test printed circuit board equipped with SiC mosfets. The results are in good agreement with the theoretical findings.