Modeling, Design, and Implementation of a Novel Transformer-less Feedforward-controlled Active EMI Filter for AC-DC Power Converters

Conducted electromagnetic interference (EMI) has been a major concern in designing power converters, requiring additional filtering components. Passive EMI filters, which are composed of inductors and capacitors, usually occupy a great portion of the volume and weight in power converters. Active EMI filters (AEF) or hybrid EMI filters (HEF) are best candidates over traditional passive EMI filters to achieve higher power density in power converters. In this paper, a novel design of transformer-less AEF is proposed with the application in AC-DC power converters. The proposed design features feedforward control and is based on the concept of virtual impedance enhancement. A prototype of proposed AEF is built and tested with a commercial power adapter in the lab. The effectiveness of the proposed AEF in conducted EMI reduction is validated through simulation and experiment.