Quantified Design Guidelines of a Compact Transformerless Active EMI Filter for Performance, Stability, and High Voltage Immunity

This paper proposes and analyzes a compact transformerless common mode active electromagnetic interference (EMI) filter (AEF) using a push-pull amplifier. Quantified design guidelines are then rigorously derived from the analysis with consideration for performance, stability, and high voltage transient immunity. The proposed AEF is manufactured based on the design guidelines, and its performance is validated by measurements using a vector network analyzer. The AEF is then implemented into a real 2.2 kW current resonant inverter, and the conducted emissions are reduced by 5-25 dB at a frequency range from 150 kHz to 6 MHz. In addition, the AEF's immunity against high voltage transients is demonstrated by lightning surge tests.