The growing attention on plug-in electric vehicles, and the associated high-performance demands, have initiated a development trend towards highly efﬁcient and compact on-board battery chargers. These isolated ac-dc converters are most commonly realized using two conversion stages, combining a non-isolated power factor correction (PFC) rectiﬁer with an isolated dc-dc converter.This, however, involves two loss stages and a relatively high component count, limiting the achievable efﬁciency and power density and resulting in high costs. In this paper, a single-stage converter approach is analyzed to realize a single-phase ac-dc converter, combining all functionalities into one conversion stage and thus enabling a cost-effective efﬁciency and power density increase. The converter topology consists of a quasi-lossless synchronous rectiﬁer followed by an isolated dual active bridge (DAB) dc-dc converter, putting a small ﬁlter capacitor in between. To show the performance potential of this bidirectional, isolated ac-dc converter, a comprehensive design procedure and multi-objective optimization with respect to efﬁciency and power density is presented, using detailed loss and volume models. The models and procedures are veriﬁed by a 3.7kW hardware demonstrator, interfacing a 400Vdc-bus with the single-phase 230V,50Hz utility grid. Measurement results indicate a state-of-the-art efﬁciency of 96.1% and power density of 2 kW/dm3, conﬁrming the competitiveness of the investigated single-stage DAB ac-dc converter.
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