Novel Zero-Current-Switching Current-Fed Half-Bridge Isolated DC/DC Converter for Fuel-Cell-Based Applications

A novel zero-current-switching (ZCS) current-fed half-bridge isolated dc/dc converter has been proposed in this paper. The proposed converter has potential applications such as front-end dc/dc power conversion for fuel cell and photovoltaic inverters, bidirectional converters for fuel cell vehicles, energy storage, etc. This proposed converter provides a simple solution to the switch turn-off voltage spike problem without any additional components or snubber. It leads to reduced size, lower cost, compactness, and higher conversion efficiency. In addition, the proposed converter has reduced peak current through the components (semiconductor devices and transformer) that reduces their volt-ampere rating and size compared to active-clamped zero-voltage-switching (ZVS) current-fed converters. Voltage across the primary switches is naturally clamped without an additional active clamp or snubber circuit. In addition, voltage across the switch is independent of the duty cycle. ZCS of the primary switches, natural commutation of secondary diodes, and zero-current turn-on of secondary switches are achieved. Therefore, switching transition losses are significantly reduced. Steady-state analysis, operation with the proposed novel ZCS concept, and design of the converter are reported. A 200-W laboratory converter prototype has been built. Experimental results as well as simulation results are presented to validate the analysis and design. A comparison with existing active-clamped ZVS current-fed half-bridge converters has been discussed. The effect of device parasitic is investigated and explained by simulation and experimental results.