Novel Transformer-Less DAB Converters for the Regulated First-Stage of a Two-Stage 48 V VRM

This paper proposes a new family of high power density Transformer-less Dual Active Bridge DC/DC converters. Each converter consists of a switched-capacitor voltage divider (SCVD) derived Switched-Capacitor Bridge circuit on the one side, a standard Half-Bridge or a Full-Bridge circuit on the other side, and a small AC link power transfer inductor connected strategically between them. The voltage matching between the two bridge circuits is achieved by changing the SCVD ratio of the Switched-Capacitor Bridge circuit. These converters have several other advantages like reduced switch voltage and current stresses, inherent soft switching for some of the switches, and efficient voltage regulation. The topological evolution of two among the proposed family of converters from their corresponding isolated versions is explained. Thereafter, the circuit operation, analysis, and experimental performance verification for one of these converters are presented. The experimental results establish the suitability of the converter as the regulated first-stage of a two-stage 48 V input VRM.