FB-ZCS DC-DC Converter with Adaptive Resonant Energy using Phase-Shift Frequency Modulation

This project presents a full-bridge zero-current switching (FB-ZCS) dc-dc converter with adaptive resonant commutation energy realized through phase-shift frequency modulation. Existing family of FB-ZCS converters use transformer leakage inductance and shunt-connected resonant capacitor for achieving smooth current commutation and soft-switching. Shunt-connected resonant capacitor unnecessarily stores full load-rated commutation energy at all load conditions and its charging duration in every switching cycle results in significant duty-cycle loss. Moreover, shunt-connected capacitor suffers from energy leakage through transformer winding which requires overrating of capacitor energy, further aggravating aforementioned issues and restricting the operation range of converter. To address these limitations, FB-ZCS converter with series connected resonant capacitor is proposed in this paper which minimizes duty-cycle loss and capacitor energy leakage. Current dependent adaptive control of resonant energy is also achieved through series connection. However, smooth commutation and soft-switching capability are lost at light loads due to insufficient voltage across resonant capacitor. To address this, frequency modulation combined with conventional phase-shift modulation control is utilized. Operation of proposed converter is presented and validated with simulation results. The simulation results can be evaluated by using Matlab/Simulink Software.

Keywords: Adaptive resonant energy, dc-dc converter, duty cycle loss, full-bridge, zero current switching.