Analysis of SiC Output Capacitance Effects on Soft-Switching Characteristics in Three-Level Resonant Converters

To address the high power density and high efficiency requirements of isolated DC/DC converters in novel power load systems, this paper investigates the soft-switching characteristics of a silicon carbide SiC-based three-level resonant converter. Through modal analysis, the influence mechanism of power device output capacitance parameters on soft-switching behavior is revealed. By comparing the impact of the presence and absence of secondary-side switch output capacitance on the soft-switching of primary-side switches, it is found that the magnetizing current required for soft-switching increases when considering the output capacitance, leading to higher conduction losses. The correctness of the magnetizing current calculation is validated through simulations. Experimental verification is conducted on a 2300V DC input / 900V DC output / 25kW prototype, demonstrating the effectiveness of the proposed design.