正态频率调制降低开关变换器电磁干扰的研究

摘要

Reduction of conducted EMI noise in switching converters using normal frequency modulation scheme （NFMS） is proposed. The principle of suppressing EMI noise under random frequency modulation scheme is analyzed briefly and an experimental prototype of the flyback converter is constructed. The power spectral densities of the MOSFET＇s current and the conducted EMI test results are presented. The experimental results demonstrate that the NFMS can reduce the peak level of the switching harmonics effectively and make the power converter pass the EMI test easily. The NFMS has applied prospect in switching converters.%利用正态频率调制技术从噪声产生源头上降低了开关变换器的电磁干扰。简单地分析了具有不变概率密度分布的离散随机信号频率调制降低开关变换器EMI噪声的原理。并试制了一台正态频率调制开关变换器电源样机。给出了开关管电流信号的频谱以及传导干扰测试的结果。实验结果表明该技术能有效降低开关谐波峰值。使开关变换器易于通过EMI测试，具有应用的前景。