Current-fed Full-Bridge Boost DC-DC Converter with Adaptive Resonant Energy

Abstract

This paper presents a current-fed full-bridge (FB) boost dc-dc converter with adaptive resonant energy for smooth current transition and zero-current-switching (ZCS). FB-ZCS converters utilize resonance between leakage inductance of transformer and shunt-connected resonant capacitor across the transformer winding to achieve the required quasi-resonant operation. Resonant energy stored in the capacitor is fixed by nature of its shunt-connection and must be designed for full-load condition. At reduced loading, full-load-rated energy is not required in the resonant capacitor and reduced current results in increased charging time and duty-cycle loss. Moreover, ZCS operation is lost under overload conditions with this arrangement. To overcome these drawbacks, an adaptive resonant energy storage and discharge mechanism using two resonant capacitors is proposed in this paper. Shunt resonant capacitor stores low energy suited for light-load conditions instead of full-load. The other resonant capacitor connected in series with the transformer-primary winding adaptively charges and stores resonant energy based on input current. Proposed arrangement doesn't require additional switches or complex control strategy and results in minimized duty-cycle loss and capability to maintain ZCS under overload conditions. Detailed converter analysis and simulation results are presented to validate the proposed idea.