Extending the range of soft-switching in resonant-transition DC-DC converters

Resonant-transition converters are attractive for high-frequency power conversion because they feature zero-voltage switching (ZVS) and low conduction loss with constant frequency, pulse width modulated (PWM) control characteristics. In many practical applications, it is difficult for these converters to sustain both ZVS and low conduction losses over a wide operating range. The use of saturable magnetic elements as snubbers for the output rectifiers and as a means to extend the range of ZVS in a phase-shifted full bridge converter is explored. A technique is described that adjusts the reset of the saturable magnetics to achieve ZVS over an extended operating range without excessive conduction losses