Four-Leaf Clover Winding Matrix Transformer with Low Winding Losses for Data Center Application

Matrix transformers can implement lower core losses and higher power density through flux cancellation, suiting for data center applications. The winding losses constitute a critical limiting factor that constrains the efficiency enhancement of matrix transformer, especially at high output current. A fourleaf clover winding (FLCW) suitable for matrix transformers with lower winding losses is proposed in this article. By lengthening and paralleling the GND layers between the synchronous rectifier (SR) MOSFETs and the output capacitances, the length of the secondary windings are shortened and the winding interleaving is improved in part of region. The proposed winding structure can optimize both primary and secondary winding losses. To substantiate the proposed FLCW, the induced electromotive force (EMF) distributes only within the core window is demonstrated theoretically and experimentally. The analysis and optimization of the proposed winding structure is presented in detail. A 1-MHz 1-kW 380 V–12 V LLC DC transformer (DCX) prototype with the proposed FLCW is built. The peak efficiency of power stage is 98.5%, and the power density is 1200 W/in³. This prototype demonstrates highest peak efficiency of power stage among published state-of-the-art LLC prototype.