A comprehensive analysis of hybrid phase-modulated converter with current-doubler rectifier and comparison with its center-tapped counterpart

A hybrid phase-modulated converter (HPMC) is a recent innovation in the family of soft-switching converters. It is a promising solution to most soft-switching issues. The principal bottleneck in achieving higher efficiency with this topology is the secondary side loss - mainly the losses in the transformer and the rectifier. For low-voltage high-current power supplies, the current-doubler rectification of HPMC addresses both the transformer conduction losses and the rectifier losses. The presence of an additional path for quiescent current in this scheme gives rise to a third mode of operation. There is also the possibility of magnetic integration of all the magnetic components into one, which can cause substantial reduction in magnetic requirements. These facts make the analysis of current doubler important. In this paper, all the operating modes are identified and corresponding equations and equivalent circuits that aid in filter and control design are derived. The zero-voltage-switching (ZVS) characteristics, filter requirement, small-signal transfer characteristics, device ratings, and magnetics size requirement are considered to compare this configuration with its center-tapped counterpart. The current-doubler scheme is found to have superior soft-switching characteristics in that it can achieve ZVS at lighter loads with a much lower peak magnetizing current in the transformer and leakage inductance. Also, a judicious choice of output current ripple can give an overall reduced magnetics requirement. The analyses are verified by simulation and hardware implementation. HPMC is found to be most advantageous for applications with input voltages essentially constant, but the output voltage widely varying, for example in battery chargers and converters with power factor correction front end.