This digest presents an integrated active EMI filter (AEF) solution targeting conducted common-mode (CM) emissions in off line power supplies. The proposed AEF comprises an IC that senses high-frequency CM noise from the power lines while rejecting the line-frequency and differential-mode components. The IC processes the sensed CM noise and injects a cancelling current back into the power lines. An analytical formulation is presented to evaluate the performance and stability of the proposed AEF. The AEF is experimentally validated with a PFC converter, demonstrating up to 25 dB noise reduction and 55% reduction in choke size for comparable EMI performance.
