High-Conversion Ratio Rippleless Bidirectional Quarter-Bridge Resonant DC/DC Converter Featuring Symmetric Operation

This article introduces a bidirectional quarter-bridge resonant dc/dc converter with a high conversion ratio and minimal current ripple. In the forward direction, the converter functions as a pulse-width-modulation (PWM) active-clamped push-pull resonant converter. In the reverse direction, it acts as a PWM quarter-bridge resonant converter. The circuit achieves a very high-voltage gain by combining an active-clamped push-pull structure on the low-voltage side and a resonant quarter-bridge on the high-voltage side. The active-clamped push-pull circuit and switching modulation fixed at a duty ratio of 0.5 produce a rippleless current at the low-voltage side. This aspect eliminates the need for an extra filter inductor. In the reverse direction, secondary-side switching prevents magnetizing current from passing through the resonant inductor, so the external resonant inductor can have a small core. This trait in the proposed converter makes its current and voltage waveforms totally symmetric in both power-flow directions. Consequently, the proposed converter offers a high-voltage conversion ratio, efficiency, and ripple-free characteristics. The feasibility of this design was demonstrated using a 1-kW laboratory prototype that operates between a low voltage range of 36 to 60 V and a high voltage of 600 V.