Conducted EMI Of Interleaved CCM Boost PFC Converter With Different Coupling Coefficients

In this paper,effects of different input voltages and coupling coefficients on the conducted EMI of the converter and the spectral characteristics of the interleaved Boost PFC converter with coupled inductor operating in CCM was studied.According to the common mode(CM)and differential mode(DM)noise characteristics of the interleaved Boost PFC converter with coupled inductor,the EMI filter of the converter under the standard limit is designed.When the interleaved Boost PFC converter with coupled inductor operates in CCM,the inductor current ripple and input current ripple were affected by the coupling coefficient of the coupled inductor.According to the relationship between the inductor current ripple and the input current ripple under different coupling coefficients,it was found that the input current ripple increases as the coupling coefficient increases.The conducted noise transmission path of the interleaved Boost PFC converter with coupled inductor was analyzed.Since the drain-source voltage of the switches of the interleaved Boost PFC converter has a large rate of change,the drain-source voltage of the two switches was regarded as source of conducted noise.Then the transmission path and equivalent model of CM and DM noise were given.Then analyze the harmonic amplitude characteristics of the noise source voltage under different coupling coefficients,and combine the noise transmission path to obtain the conducted EMI spectrum.It was found that CM noise and DM noise only occur in the even multiple of the switching frequency.The CM noise was independent of the coupling coefficient.The amplitude of the CM noise was almost the same as the frequency increases.The DM noise increased as the coupling coefficient increases,and the DM noise attenuates with a slope of-60 dBμV/dec as the frequency increases.Finally,simulation results and experimental verification waveforms were given.The conducted noise of the designed interleaved Boost PFC converter with coupled inductor exceeded the standard limit requirements.A typical EMI filter was selected according to the spectral characteristics of the converter,and the appropriate coupling coefficient α=0.79 and the component parameters of the EMI filter were given according to the worst case spectrum and power density.Finally,the simulation results and experimental verification waveforms was given.