Characterizing the Influence of Circuit Parasitics and Operating Conditions on a Passive Regenerative Snubber for Phase-Shifted Full-Bridge Converter

The Phase-Shifted Full-Bridge converter is a fairly simple to control soft-switching DC-DC converter but experiences high-voltage oscillations across the diodes of the secondary bridge. Various passive and active snubber circuits have been employed to clamp these secondary voltage overshoots, but both approaches have limitations: passive snubbers are simple but reduce efficiency, while active snubbers improve performance at the cost of increased circuit complexity and additional control requirements. This paper presents a detailed analysis of a recently introduced passive regenerative snubber. The study examines the influence of converter and snubber parasitics, as well as load current ripple, on the converter operation and snubber’s performance. Closed-form expressions for the state variables in each topological stage are derived to accurately capture the converter’s behavior. The theoretical analysis is validated through experimental results obtained from a 400 V to $48 \mathrm{~V}, 1.5 \mathrm{~kW}$ hardware prototype, demonstrating the significant effects of the aforementioned factors.