EMI performance comparison of switched-capacitor bidirectional converter with and without QR ZCS

The EMI performance of a non-isolated bidirectional switched-capacitor (SC) converter with quasi-resonant (QR) zero current switching (ZCS) converter is proposed in this paper. The quasi-resonant switched-capacitor converter presents low conducted EMI noise due to the sinusoidal resonant current advantages. Theoretical analysis and EMI measurement for the proposed bi-directional power conversion scheme is performed using a detailed equivalent circuit model and field test, respectively. The conducted common-mode (CM) and differential-mode (DM) noises could be separated using a power combiner from the converter circuit noises. Experimental verification is carried out to verify and compare the proposed QR ZCS SC bi-directional converter EMI performance with the conventional hard-switching device. Peak level EMI emissions in the measured frequency spectrums show the proposed device can significantly reduce from 1.5-14.3 dB¿V compared with that measured in the converter without QR ZCS for the forward and reverse power flow control schemes at a specified frequency range. The radiated emissions are improved as well. It can also be observed from the CM/DM separated measurement experimental results that the DM noises are dominant. This may present better EMI suppression when designing the power line filter.