Fixed-frequency phase-controlled full-bridge resonant converter with a series load

A fixed-frequency phase-controlled full-bridge parallel resonant converter (PCPRC) that consists of a phase-controlled parallel resonant inverter (PCPRI) and an input-inductor rectifier is analyzed. The input impedances of the resonant circuits represent inductive loads for both switching legs at f/f₀>1.24 and therefore zero-voltage-switching turn-on can be achieved for all the transistors. The fundamental frequency approximation is used to derive expressions for the voltage transfer function and the efficiency of the PCPRI. The behavior and performance characteristics of the PCPRI are then studied. Three types of input-inductor rectifiers are considered and a design procedure is developed. A 30 W PCPRC is designed and tested. The theoretical calculations were in good agreement with experimental results. The converter exhibits an excellent efficiency. The measured efficiency was 92% at full load. The converter is capable of regulating the DC output voltage from full load to no load and over a wide line voltage range