Highly Efficient Full-Bridge Resonant AC/DC Converter Using T-Type Voltage Doubler

This article presents full-bridge resonant ac/dc converter that minimizes switching loss over entire grid voltage cycle. By using the voltage fluctuation at T-type voltage doubler, the existing hard-switched components are turned-off with almost zero-voltage switching at high instantaneous output power and with less than half of the output voltage at low instantaneous output power. Moreover, no instantaneous reactive current flows through the circuit under wide variations of grid voltages and loads. Furthermore, the proposed converter has balanced loss distribution over the primary-side and secondary-side switches, which ensures high power transfer capability with improved overall switch utilization. A 1-kW prototype is developed and tested to demonstrate the circuit functionality. Finally, the efficiency improvement is investigated; comparisons show the benefit of the proposed converter over conventional converters that use unfolders.