High efficiency PWM zero-voltage-transition DC-DC boost converter

Abstract

A soft-switching boost converter with duty-cycle control is proposed. Compared to its hard-switching PWM counterpart, the new switch-mode converter contains four additional elements: a resonant inductor, an active switch and two diodes. The parasitic capacitances of the main and auxiliary active switch serve as resonant capacitors. Multi-resonance is created in the circuit, thus allowing for zero-voltage-switching of the active switches and rectifier diode. The commutation of all switches takes place with zero capacitive turn-on losses; consequently, the switching losses are small. The current through the resonant inductor is not allowed to increase over the load current; the resonant stage is delayed until the inductor has been discharged. As a result, the voltage and current stresses on the devices are at the same level as on their counterparts in conventional converters, implying normal-rated switches, and normal conduction losses. The overall efficiency is very high, as proved by the measurements on a prototype realized in the laboratory.