开关变换器高频磁损建模及其定量计算方法的研究

For the manufacturer's supplied loss data is usually available for sinusoidal waveforms only, the loss density caused by actual waveform may exceed the loss density for the sinusoidal waveform, even when the frequency and the peak flux density are the same. In this project, we are driven by the requirement that the model be simple enough and research a new approach for the core loss calculations in case of nonsinusoidal voltage waveforms in switched-mode power supply (SMPS). First, The eddy current loss defined in this project is consisted of classical eddy current loss and excess eddy current loss. The effect of the excess eddy current loss is approximately taken into account by adjusting the value of resistivity in the formula for classical eddy current loss. The piecewise linear model is used to represent any value of resistivity in accordance to frequency. Secondly,we plan to calculate the ferrite hysteresis losses based on empirical rules. As a result, the proposed core loss seperated model based on sinusoidal ferrite loss data is very simple and accurate since it takes into account all the three well known components of the high frequency magnetic loss. Thirdly, the variation of flux in the magnetic components is always constant, the changed character of hysteresis losses under the different DC biased magnetic conditions is analysed,and a simplified model is proposed to describle this phenomena. Fourthly,the different duty cycles, control modes and topologies will cause the different excitation waveforms, we analysis their effect to eddy current loss. Since any loss component contribution depends on the excitation waveform characteristics, it is possible to find a direct mathematical relationship between the sinusoidal waveform and the excitation waveform characteristics at the same frequency and the peak flux density. As a consequence, the method is presented for computing high-frequency ferrite core losses in the SMPS for arbitrary working conditions and topologies. Our approach can be a useful support for electrical designers to estimate core loss to avoid uncontrolled temperature rise.

由于存在磁性材料、直流偏磁、拓扑架构、控制策略、占空比等差异，建立普适性的磁芯损耗模型存在显著挑战。本项目充分结合开关变换器中高频变压器和滤波电感等主要磁性元件的工作特点，探索建立磁芯损耗简化理论模型及其实现定量计算的方法。主要研究内容是：利用线性插值法调整不同频率下的电阻率，将剩余损耗中额外涡流损耗的影响涵盖在经典涡流损耗的计算中，以简化磁损3项构成理论模型；根据厂家给出的正弦波激励下磁芯损耗曲线数据构建磁损分离方程分离磁滞损耗和涡流损耗，可避免不同磁芯材料特性系数对磁损建模的影响；结合磁芯工作时磁通密度变化量近似恒定的特点，利用磁芯直流B-H曲线建立在不同直流偏置条件下磁滞损耗变化特征的简化等效模型；比较典型拓扑激励波形与正弦波激励造成的涡流损耗差异，并建立与之对应的数学关系。通过该项目的研究可以深刻揭示不同因数对磁芯损耗的具体影响，为开关变换器磁芯损耗定量计算提供有力的理论分析工具。

背景：由于存在磁性材料、直流偏磁、拓扑架构、控制策略、占空比等差异，建立普适性的磁芯损耗模型存在显著挑战。本项目充分结合开关变换器中磁性元件的工作特点，建立磁芯损耗理论简化模型并实现定量计算。.主要研究内容：（1）利用线性插值法调整不同频率下的电阻率，将额外涡流损耗的影响涵盖在经典涡流损耗的计算中，以简化磁损3项构成理论模型；（2）根据正弦波激励下磁芯损耗数据，构建磁损分离方程分离磁滞损耗和涡流损耗，避免使用磁芯材料特性系数对磁损建模；（3）结合磁芯工作时磁通密度变化量恒定的特点，利用磁芯直流B-H曲线建立在不同直流偏置条件下磁滞损耗变化特征的简化等效模型；（4）比较典型拓扑激励波形与正弦波激励造成的涡流损耗差异，建立对应的数学关系；（5）根据实际磁性元件所承受的直流偏磁、激励波形等条件差异，研究典型拓扑架构下功率磁芯损耗的定量计算方法。.重要成果:（1）基于两个频率点正弦激励下的损耗数据，提出了分离磁滞损耗和涡流损耗的方程；（2）建立了在相同频率和磁通密度变化量条件下矩形波激励和正弦波激励之间的对应关系，可有效分析各类拓扑的高频变压器损耗；（3）提出了定量描述直流偏置对磁滞损耗的影响物理模型，可用于反激变换器、Buck和Boost变换器输出电感的磁芯损耗预测；（4）开发了基于Labview软件的磁损自动测试界面和基于DDS数字合成技术的正弦激励源信号板，通过整合功率放大器、高精度功率分析仪等设备构建了磁损自动测试平台。目前系统已经研发成功，测试精度达到专业级设备。.关键数据及其科学意义：磁性元件材料种类繁多、不同拓扑工作状态差异较大，本项目建立的高频磁损模型能准确预测功率磁芯在不同占空比、频率、拓扑和直流偏置条件下的大小，适用于工程应用并具有较高的精确性。通过该项目的研究深刻揭示不同因数对磁芯损耗的具体影响，为开关变换器磁芯损耗定量计算提供有力的理论分析工具。