考虑漏磁特性的变压器电磁干扰特性模型

摘要

Transformers are the key components in isolated switching mode power supplies to affect their electro-magnetic interference (EMI)characteristics.When using previous three-capacitor EMI model to evaluate the EMI noise,the error is greater than prediction when the noise frequency is high or when the transformer turns ratio is small.In this paper,firstly the influence of leakage magnetic field on noise potential distribution was analyzed,complemented with the effect of the secondary side coupling.Secondly the influences of the turn ratio structures on the EMI noise were compared and summarized.Based on these analyses,an improved EMI model of transformer with the consideration of leakage magnetic field was proposed.The proposed model was evaluated by using the parameter measurement method,which could describe the two-port characteristics of a transformer.Both experiment and simulation results confirm the theoretical analysis and model.%变压器是隔离型功率变换器电磁干扰(EMI)噪声传输的关键器件.针对先期建立的变压器三电容容性EMI噪声特性模型在评估小匝比变压器及高频噪声时误差增大的现象,首先分析高频下变压器漏磁对噪声电压分布的影响,然后补充变压器二次侧耦合噪声对电磁噪声的影响情况,对比总结不同匝比结构对变压器噪声影响因素,在此基础上提出考虑漏磁特性的变压器EMI特性模型.通过能反映变压器二端口特性的参数测量评估方法进行实验评估,实验和仿真结果验证了理论分析和模型的正确性.