High-efficiency high-power-density 380V/12V DC/DC converter with a novel matrix transformer

Isolated high output current DC/DC converters are critical for future data center power architecture. LLC converters with matrix transformer are suitable for these applications due to its high efficiency and high power density. Different matrix transformer structures are investigated. Flux cancellation can be utilized to reduce core size and loss. Synchronous rectifiers and output capacitors can be integrated into the secondary windings to minimize leakage and termination loss. To further improve the current design practice, several efforts have been made and a detailed design procedure is provided in this paper. A novel matrix transformer structure is proposed to integrate four elemental transformers into one magnetic core with simple four-layer PCB windings, fully utilize the available PCB copper and space, and further reduce core loss. The proposed matrix transformer is superior to the state-of-art, due to the much reduced core loss, integrated magnetics and simple four-layer PCB winding. With the proposed matrix transformer, LLC converter can achieve both high efficiency and high power density by operating at MHz. A 1MHz 380V/12V 800W LLC converter with GaN devices is demonstrated. The prototype can fit into the quarter-brick footprint and achieves a peak efficiency of 97.6% and a power density of 900W/inch³.