An Active EMI Filter for Common-Mode EMI Mitigation in High- Power AC Systems

This paper introduces an active electromagnetic interference filter solution that can substantially reduce the size, weight and cost of common-mode chokes in off-line switching power regulator designs. The proposed active solution uses a voltage-sense, current-injection topology, employs capacitors for sensing and injection and does not require additional magnetics. It rejects line-frequency (50 Hz or 60 Hz) AC voltage and amplifies high-frequency CM noise using an integrated circuit (IC) solution, while maintaining closed-loop stability using an external tunable damping circuit. The solution is experimentally validated on a totem-pole power factor correction (PFC) AC/DC regulator, demonstrating 52% reduction in choke box volume while maintaining similar EMI performance.