Optimal Design of Transformer Winding of LLC Converter
Wang Yifeng1, Chen Chen1, Chen Bo1, Zhang Shuangle2, Zhang Mingzhi1
1. Key Laboratory of Smart Grid of Ministry of Education Tianjin University Tianjin 300072 China; 2. State Grid Dongying Electric Power Dongying 257091 China
Abstract：Due to LLC resonant converter is sensitive to the parasitic capacitance of planar transformer at high frequency, the magnetic integration technology is used to optimize the winding of the transformer, so that the comprehensive effect of parasitic capacitance and solid loss of the transformer is optimal. In this paper, the influential factors of parasitic capacitance between layers of planar transformer are analyzed in detail. The mathematical model of parasitic capacitance of transformer is established in polar coordinate system, and the effect of each influential factor under different current conditions is summarized. Two optimal design implementations of winding shape are proposed to improve the parasitic capacitance of transformer by reducing the opposite area of winding. The 3D simulation model of the transformer is built with the FEA simulation software Maxwell. According to the simulation results, the improvement of parasitic capacitance with the two proposed optimal implementations is compared, and the reliability of theoretical analysis is verified. To compromise the parasitic capacitance and solid loss of the transformer, the optimal design range of winding area is given. At the same time, the final implementation is determined. Finally, a 500kHz 500W LLC prototype is demonstrated with the improved magnetically integrated planar transformer, and the peak efficiency of 97.53% is achieved.
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2022, Vol. 37 
