A novel design and performance characterization of a very high current low voltage dc-dc converter for application in micro and mild hybrid vehicles

This research proposes a new single-phase two-level design for a very high current low voltage unidirectional dc-dc converter. The targeted converter is a 48-to-13.3 V, 250 A converter used in dual voltage architecture of micro and mild hybrid vehicles. A novel solution integrating a single-winding self-driven synchronous rectification technique into phase-shifted full-bridge topology (PSFB) has been proposed for the design. The proposed design eliminates body diode conduction and reverse recovery loss in synchronous rectifier (SR) MOSFETs used in the PSFB topology. It also achieves ZCS turn-off of SR MOSFETs thus reducing their switching loss. Moreover, due to the single-phase design, it offers a more cost effective solution with less device count and simpler control, as compared to multiphase designs proposed in the past for similar high current low voltage converters. Performance of the new design approach has been characterized and compared with traditional PSFB topology with control driven synchronous rectification in terms of converter efficiency, size, and thermal requirements.