平面变压器绕组高频损耗的研究

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平面变压器绕组高频损耗的研究
图 表 清 单
图 1.1 一种亚微米型平面变压器外型图 .................................................................. 5 图 1.2 将一维线圈等效为铜箔进行一维分析 .......................................................... 6 图 1.3 PAYTON 公司生产的平面变压器 .................................................................. 7 图 2.1 平面变压器典型结构 ...................................................................................... 9 图 2.2 平面 E 型磁芯和 RM 型磁芯 ........................................................................11 图 2.3 平面变压器结构示意图 .................................................................................11 图 3.1 一层铜箔示意图 ............................................................................................ 18 图 3.2 薄铜箔一维情况下集肤效应磁场分布 ........................................................ 19 图 3.3 Ps 随 λ 变化的曲线 ....................................................................................... 21 图 3.4 薄铜箔一维情况下邻近效应磁场分布 ........................................................ 22 图 3.5 Pp 随 λ 变化的曲线 ....................................................................................... 25 图 3.6 薄铜箔一维情况下涡流效应的磁场分布 .................................................... 26 图 3.7 P 随 λ 变化的曲线 ........................................................................................ 28 图 4.1 一层厚绕组 .................................................................................................... 31 图 4.2 两层薄绕组的并联 ........................................................................................ 31 图 4.3 两层薄绕组并联和一层厚绕组 .................................................................... 32 图 4.4 不同绕组布置时在 500KHz 下的单位长度损耗值 ..................................... 33 图 4.5 绕组结构示意图 ............................................................................................ 33 图 4.6 沿 A － B 线绕组各层电流密度分布图 ........................................................ 34 图 4.7 沿 A′ － B′ 线绕组各层电流密度分布图 ....................................................... 34 图 4.8 两层并联绕组闭合回路中各物理量关系 .................................................... 35 图 4.9 不同频率下绕组各层电流密度分布图 ........................................................ 36 图 4.10 不同频率下单位长度的绕组损耗比较 ...................................................... 36 图 4.11 绕组交叉换位结构示意图........................................................................... 37 图 4.12 500KHz 频率下不同绕组结构方式单位长度的绕组损耗 ......................... 37 图 4.13 500kHz 完全交叉和对称交叉布局各层电流密度分布图 ......................... 38 图 4.14 500KHz 下不同绝缘层厚度的电流密度分布图 ......................................... 38 图 4.15 100KHz 下不同绕组层厚度的电流密度分布图 ......................................... 39
南京航空航天大学 硕士学位论文 平面变压器绕组高频损耗的研究 姓名：祝锦 申请学位级别：硕士 专业：电力系统及其自动化 指导教师：龚春英 20080101
南京航空航天大学硕士学位论文摘 Nhomakorabea要
与传统绕线式变压器相比，平面变压器具有相当多的优点，例如低造型、 良好的散热特性、漏感小、可实现特性重现等等，适用于高功率密度高频开关 电源。平面变压器的研究和应用在过去十年得到了快速发展。然而，当开关频 率高达数百 KHz，甚至大于 1MHz 时，平面变压器受到诸如集肤和邻近效应等 高频效应的影响。这些高频效应产生的交流电阻、漏感增大了开关电源的损耗， 降低了开关电源的性能，因此平面变压器的优化设计必须考虑所有高频效应的 影响。 本文从 Maxwell 电磁场方程组出发，在一维情况下对薄铜箔的集肤效应和 邻近效应引起的损耗进行了研究，得出薄铜箔总的涡流损耗是集肤和邻近效应 单独起作用产生损耗的总和。 运用 Ansoft 公司的 Maxwell 2D 电磁场仿真软件对 多层绕组并联在高频时带来的问题进行了研究，说明了简单的绕组并联并不能 减小高频损耗，并且分析了在并联绕组中产生不均流的原因，对影响并联 PCB 线圈中电流分配的重要因素进行了研究。同时对平面变压器原副边绕组利用交 叉换位技术减少高频损耗在不同类型变压器中的运用进行了深入研究，详细说 明了在不同类型变压器中如何具体运用交叉换位技术来减小绕组的高频损耗。 随后在考虑高频开关电流及其谐波的情况下对不同的交叉换位方案进行了分 析，提出了绕组交叉换位设计必须考虑全部电流分量，不能只针对某一频率设 计。最后分析了绕组边缘效应对高频损耗和漏感的影响。 本文最后详细阐述了基于反激变换器的平面变压器的设计过程。根据前面 的理论分析，设计制作了三种不同绕组布局的平面变压器，并和普通绕线式变 压器进行了实验对比，实验结果表明原副边绕组交叉换位布局的平面变压器性 能优良，显著的提高了变换器的效率。 关键词：平面变压器，PCB，集肤效应，邻近效应，交叉换位， Maxwell
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平面变压器绕组高频损耗的研究
ABSTRACT
Compared to the conventional wire wound transformer, planar transformer offers many advantages, such as low profile, good thermal characteristic, small leakage inductance and well repeatability, so it is a good solution for high power density and high frequency switch mode power supplises (SMPS).Its research and application are growing in the last decade. However, due to the high switching frequency up to several hundreds kHz, even more than 1MHz, planar transformer is also affected by many high-frequency effects like skin and proximity effects. These high-frequency effects produce ac resistance and leakage inductance that increase the losses of the SMPS, and the performance of the SMPS is reduced significantly. Hence an optimal design of planar transformer should be take into account the high frequency effects. This paper started from Maxwell field equations, thin copper foil the losses caused by skin and proximity effect were studied in the case of one-dimensional. To study the problems of parallel winding layers for high-frequency planar transformer, the Ansoft Maxwell 2D electromagnetic field simulation software was used.The results showed that a simple parallel winding layers arrangement can not reduce the high-frequency losses. Factors affecting the current distribution for parallel winding layers were identified, and the general rules for reducing the unbalance of current distribution among parallel winding layers were presented. At the same time, former vice-planar transformer windings useing interleaving techniques to reduce high-frequency losses in different types of transformers was deeply studied and how to reduced high-frequency losses by interleaving techniques in different types of transformers was analyzed.Then the different interleaving schemes in the condition of high-frequency switching mode were discussed. All the current components including harmonics should be take into account in the interleaving schemes, it’s insufficient that only a certain frequency is concidered.Finally fringing effect on high-frequency losses and leakage inductance was analyzed. At last the design process of a flyback converter based on planar transformer is expatiated in detail. According to previous theoretical analysis, three different