LLC谐振变换器的变压器绕组优化设计

Optimal Design of Transformer Winding of LLC Converter

针对LLC谐振变换器工作在高频条件下对平面变压器寄生电容较为敏感的问题,采用磁集成技术对变压器的二次绕组进行优化设计,使得变压器寄生电容和绕组涡流损耗的综合效果最优。该文对平面变压器层间寄生电容的影响因素进行了具体分析,在极坐标系下建立变压器寄生电容的数学模型,并归纳出各影响因素在不同电流情况下的作用效果。该文提出了两种绕组形状的优化设计方案,从减小绕组正对面积的角度改善变压器的寄生电容。利用有限元仿真软件Maxwell,搭建变压器的3D仿真模型,根据仿真结果对比了采用不同优化方案时寄生电容的改善效果,验证了理论分析的可靠性。为了兼顾变换器的寄生电容和涡流损耗,给出了绕组面积设计的优化范围,并确定了最终的优化方案。最后,采用改良后的磁集成平面变压器,搭建了一台500W的样机,效率最高可达97.53%。

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 3 D 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 500 kHz 500 W LLC prototype is demonstrated with the improved magnetically integrated planar transformer, and the peak efficiency of 97.53% is achieved.