A new soft-switched resonant buck-type rectifier with constant switching frequency

A new three-phase soft-switched AC-to-DC buck converter operating at constant switching frequency and drawing current at unity power-factor from the source is proposed. Unlike other three-phase resonant switch buck-type rectifiers reported in the literature, the switching frequency of this converter is held constant. The proposed converter uses two switches, which are soft-switched. This results in reduced switching losses and electromagnetic interference (EMI). The principle of operation and detailed analysis of the converter are given and the design procedure of the rectifier is presented. In order to predict the performance of the proposed rectifier, detailed simulation studies using SABER are carried out. A laboratory prototype of the rectifier operating from three-phase 110-V_{rms (L-L)} 50 Hz supply and delivering 250 W at 50 V is designed and developed. The source current is sinusoidal and power-factor is unity. The total harmonic distortion (THD) of the line current is less than 5% at full load.