An isolated three-phase soft-switched buck rectifier

In this paper a novel soft switching isolated buck rectifier is proposed. Various switching state sequences of a three-phase three-switch buck-type unity power factor rectifier are reviewed and the value of switching power loss in each state transition is investigated. The switching power loss of the converter is decreased by using zero current switching (ZCS) method. The operation modes of the converter are explained and analyzed. By using an auxiliary circuit with a simple method of energy recovery, the current is diverted away from the main power switches before they are turned off; so, switching losses in the converter are reduced. In this topology, the power transformer has only the primary and the secondary windings and the transformer is demagnetized in each switching period without the demagnetizing winding. The auxiliary circuit consists of an auxiliary switch and a resonant inductance-capacitance circuit connected to the auxiliary switch. The proper operation of the converter is confirmed by the results obtained from the digital simulations.