A Novel Active EMI Filter Based on Transferring Common-Mode Noise to Differential-Mode Noise

This letter proposes a novel common-mode (CM) to differential-mode (DM) active electromagnetic interference (EMI) filter (C2D-AEF). First, CM noise is transferred to DM noise by an active circuit. Then, DM noise can be reduced by an X-capacitor with ease. Therefore, equivalently, CM noise can be eliminated. This is achieved by setting the AEF reference on the negative bus and sensing/injecting EMI noise from/to the ground. Advantages of the proposed C2D-AEF lie in that there is no need to separate CM/DM noise, no need for a sensing capacitor, and only one injecting capacitor and one X-capacitor are needed. Moreover, the topology only operates in a low-voltage stress environment, which can have better stability. Experimental results show that the proposed C2D-AEF has a good attenuation effect on both CM and DM noises, with high density and small size.