Multiport Resonant GaN-based DC/DC Converter for Automotive On-board Low-Voltage Bus

High voltage (HV) batteries, from 400V up to 800V, are a recent breakthrough in the automotive field. These batteries along with the required power converter are able to provide higher efficient systems with enhanced power density, at the same time faster charging speeds can be achieved. Depending on the automobile manufacturer and the electric vehicle type, multiple DC buses of HV and LV are employed simultaneously, which demands several conversion stages. For this purpose, isolated multiport DC/DC converters are a promising solution to adapt these different HV and LV levels while allowing a reduced number of conversion stages and high efficiency. This is only achievable because a multiwinding transformer (MWT) is used to couple the multiple cells and hence compose the overall multiport DC/DC converter. Therefore, in this paper, a GaN-based multiport resonant converter with a wide input voltage range is investigated to interconnect multiple HV and LV DC buses. To reduce the voltage and current effort of the GaN devices, the approach employs an input-series and output-parallel interconnection (ISOP). Further, as a novel approach, only one resonant tank on the input side is used to reduce parameter deviations among the multiple ports. Finally, the investigated topology is validated in simulation as well as by means of a hardware demonstrator with a peak efficiency of 94.23%. Index Terms-DC/DC Converter, GaN, Low-Voltage Bus, Multiwinding Transformer, Multiport, Power Conversion, Resonant Converter, Synchronous Rectification