FIXED-FREQUENCY PHASE-CONTROLLED FULL-BRIDGE RESONANT CONVERTER WITH A SERIES LOAD

A fixed-frequency phase-controlled full-bridge parallel resonant conve rter (PCPRC) that consists of a phase-controlled parallel resonant inv erter (PCPRI) and an input-inductor rectifier is analyzed. The input i mpedances of the resonant circuits represent inductive loads for both switching legs at f/f0 > 1.24 and therefore zero-voltage-switching tur n-on can be achieved for all the transistors. The fundamental frequenc y approximation is used to derive expressions for the voltage transfer function and the efficiency of the PCPRI. The behavior and performanc e 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 we re 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 fu ll load to no load and over a wide line voltage range.