A new, two-switch, isolated, three-phase AC-DC converter

In this paper, a new, three-phase, single-stage, isolated ac-dc converter (rectifier) that employs only two switches and achieves less than 5 % total harmonic distortion (THD) of the three-phase input currents and provides a tightly regulated, isolated, output voltage is introduced. The rectifier features zero-voltage-switching (ZVS) of both switches over the entire input and load range without any additional soft-switching circuitry. The rectifier is derived by combining the three-phase, frequency-controlled, power-factor-correction (PFC), discontinuous-current-mode (DCM) boost rectifier with the conventional LLC resonant half-bridge converter. The evaluation was performed on a 1-kW prototype operating with a three-phase line-voltage range from 180 V L-L to 264 V L-L and delivering a tightly-regulated, isolated, output voltage of 54 V.