基于噪声源阻抗提取的LED驱动电源EMI滤波器设计

Electromagnetic Interference Filter Design of LED Driver Based on the Noise Source Impedance Extraction

EMI滤波器是开关电源满足电磁兼容标准的关键手段。本文基于噪声源阻抗提取对EMI滤波器进行设计。首先推导了滤波器插入损耗与噪声源阻抗的数学关系式,并给出滤波器结构的选取准则;然后基于插入损耗法提取了噪声源阻抗的最大值与最小值,并根据提取的噪声源阻抗的幅值范围分别设计了CL型共模滤波器和π型差模滤波器;最后将CL型共模滤波器与常用的LC型共模滤波器的滤波效果进行对比,验证了基于噪声源阻抗设计滤波器的必要性,并将依据噪声源阻抗设计的共模和差模滤波器加入实验样机中进行测试。实验结果表明,基于噪声源阻抗设计的EMI滤波器针对性强,同时能够大幅减少EMI滤波器设计过程的时间成本。

EMI filter is vital for switching power supply to meet EMC standards.This paper designs EMI filter based on noise source impedance extraction.Firstly, the mathematical relationship between filter insertion loss and noise source impedance is deduced, and the selection criterion of filter structure is given.Then the maximum and minimum impedance of noise source are extracted based on the insertion loss method, and according to the amplitude range of the extracted noise source impedance, CL-type common mode filter and π-type differential mode filter are designed respectively.Finally, the filtering effect of CL-type common mode filter is compared with that of LC-type common mode filter, which verifies the necessity of designing filter based on noise source impedance, and the designed common mode and differential mode filters are added to the experimental prototype for testing.The experimental results show that the EMI filter designed based on noise source impedance is highly targeted, and can greatly reduce the time cost of EMI filter design process.