High frequency range conducted common-mode noise suppression in SMPS

In power electronics system, high frequency range CM noise suppression is a great challenge on the issue of conducted EMI. People may think that a perfect EMI filter with little self parasitics and mutual parasitics would suppress HF noise well. However, it will be shown that the practice story is different. In this paper, besides the parasitics in EMI filter, some other factors which increase the difficultly of high frequency range CM noise suppression are discussed. HF noise model and noise transmitting path are given. Based on the noise model, noise suppression techniques are analyzed and verified with experimental results.