Coupled inductor based single-phase bridgeless PFC boost rectifier with auxiliary circuit assisted ZVS

Front end PFC (power factor correction) boost ac-dc converter is an intrinsic part of applications like telecom servers, electric vehicle (EV) charging, and microgrids. In this paper a bridgeless PFC boost rectifier with two dc/dc boost circuits topology is employed to convert universal ac input to a fixed and regulated output dc voltage. High efficiency and power density are key figure-of-merits of boost PFC ac-dc converters. In this converter the conduction losses are reduced owing to the bridgeless topology and the boost diode reverse recovery is eliminated using MOSFETs for synchronous rectification. The converter operates in continuous conduction mode (CCM), at a switching frequency of 500 kHz. At high switching frequency and at CCM, soft-switching is necessary, therefore a passive auxiliary circuit is used to achieve zero voltage switching (ZVS). In order to increase the power density, the boost and the auxiliary inductors are magnetically coupled with a very low coupling coefficient. This coupling reduces the volume of the magnetics, although there is some loss due to the additional circulating current resulting from the coupling, however this loss is not that significant. Although passive auxiliary circuit adds more components, however at 500 kHz switching frequency these passive components do not occupy significant space. The soft-switching improves the efficiency and reduces EMI noise and cooling requirements. The detailed analysis, design and simulation results using PSIM are provided to validate the theoretical claims.