A Family of Novel Zero-Voltage and Zero-Current Switching Full Bridge Converters Using Output Voltage Reset for Fuel Cell Application

A new family of output voltage reset circuits for ZVZCS full-bridge converter is proposed in this paper for fuel cell converter applications. Detailed circuit operation is described with topological changes in each stage of state transitions. Conditions that satisfy the transformer current reset were expressed mathematically. A low-voltage input converter hardware has been built and tested using a fuel cell simulator as the source to demonstrate the main features and advantages of the proposed converter. Major voltage and current waveforms are compared with undamped and conventional RCD clamped circuits. Efficiency evaluation indicates an improvement over RCD clamped type converter, especially in low-power low-duty cycle regions. The proposed circuit clearly shows effective circulating current reset for ZVZCS operation and voltage clamping features without lossy component.