Study of the applicability of self-driven synchronous rectification to resonant topologies

Synchronous rectification techniques applied to high-frequency resonant topologies are studied. The on-resistance reduction of the MOSFET synchronous rectifier produces an increase of the parasitic capacitances. A selection of the resonant topologies where these capacitances are absorbed by the resonant tank, allowing self-driving of the synchronous rectifier, is presented. High efficiency has been obtained in a low-output-voltage (5 V and 3.3 V) forward ZVS-MRC with resonant synchronous rectification. Layout effects appeared to be very important at high switching frequencies. Even better results are expected in a hybrid prototype using specific low gate resistance MOSFETs as synchronous rectifiers.<
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