Research on Effects of Clamping Diodes Parasitic Capacitance on PSFB Converter

The phase-shifted full-bridge (PSFB) converter can achievie Zero Voltage Switching (ZVS) in power switches, a kind of converter commonly applied in medium to high power applications. However, in this converter, the resonant inductor interacts with the parasitic capacitance of the rectifier diode. This interaction results in a rapid increase in voltage stress on the rectifier diode, posing a significant safety risk to its normal operation. Currently, the prevailing approach to mitigate the voltage oscillation issue involves the integration of clamping diodes on the primary side of the converter. These converters can be categorized into two types: Tr-lag and Tr-lead, based on the connection position of the transformer and resonant inductor. It is worth noting, though, that clamping diodes are not ideal components, and their incorporation into the converter introduces additional parasitic capacitance. This paper conducts a comprehensive analysis of the operational principles underlying these two types of PSFB converters while considering the impact of clamping diode parasitic capacitance on their characteristics. Additionally, the research includes the development of an experimental prototype based on theoretical foundations. The experimental waveforms closely align with the theoretical analysis, confirming the accuracy and soundness of the theoretical framework.