Optimal Design of a Matrix Planar Transformer in an LLC Resonant Converter for Data Center Applications

The 48V bus converter has been gradually adopted in intermediate bus architecture. The ever-growing development of data centers consumes significant power, and thereby pushing power converters to be more efficient. This paper focuses on the optimization of the transformer for a LLC resonant converter used in data centers, which is the second stage operating as a DC transformer to realize the isolation and a fixed voltage step-down ratio. The front stage is a multiphase buck converter. The magnetic core geometry reported in this paper for the LLC enables a single turn for both primary and secondary windings. Compared with the previous research, the improved interleaving winding scheme benefits from reduced conduction path, lower AC resistance and smaller core volume. Ansys 3D simulation performs the design and optimization of the magnetic core. The proposed magnetic core, winding layout and design optimization are verified in the 30/5V 660W LLC resonant converter. It has higher current stress, but achieves a higher efficiency of 97.7%, better thermal performance, and lower components count than the state-of-the-arts.