Elimination of transformer magnetizing current offset for digitally controlled phase-shift full-bridge converter

A transformer magnetizing current offset for a phase-shift full-bridge (PSFB) converter is dealt in this paper. A model of this current offset is derived and it is presented as a first order system having a pole at a low frequency when the effects from the parasitic components and the switching transition are considered. A digital offset compensator eliminating this current offset is proposed and designed considering the interference in an output voltage regulation. The performances of the proposed compensator are verified by experiments with a 1.2kW PSFB converter. The saturation of the transformer is prevented by this compensator.