A MOSFET resonant synchronous rectifier for high-frequency DC/DC converters

A resonant synchronous rectifier which combines the fast switching of Schottky diodes with low conduction drop of MOSFET devices is discussed. The MOSFET devices are driven in a resonant fashion by the power circuit, resulting in partial recovery of the energy stored in the parasitic capacitances. Power loss in the resonant synchronous rectifier is determined as a function of various devices parameters and switching frequency. Contributions of conduction losses, gate-drive switching losses, and losses due to current circulating in the parasitic capacitances are discussed. The analysis indicates that, at megahertz range switching frequencies, a resonant synchronous rectifier has a significantly higher efficiency than either a PWM (pulse width modulation) synchronous rectifier or a Schottky diode rectifier.>