A NEW PHASE-CONTROLLED PARALLEL RESONANT CONVERTER

A new phase-controlled resonant inverter is obtained by paralleling th e ac loads of two identical parallel resonant inverters. A phase shift between the drive signals of the two inverters controls the amplitude of the output voltage of the new inverter. A voltage-driven rectifier is used as an ac load of the inverter which results in a phase-contro lled parallel resonant dc-dc converter. A frequency-domain analysis is performed for the steady-state operation of the inverter and two type s of voltage-driven rectifiers and design equations are derived. The c onverter can be operated at a constant switching frequency which reduc es EMI problems. It is found that for switching frequencies higher tha n the resonant frequency by a factor of 1.07, the load of each switchi ng leg is inductive which allows for the use of power MOSFET's as swit ches. The converter is capable of regulating the output voltage in the range of load resistance from full load to no load. An experimental p rototype of the phase-controlled parallel resonant converter with a ce nter-taped rectifier was built and extensively tested at an output pow er of 50 W and a switching frequency of 116 kHz.