Analytical Modeling and Stability Characterization of a Damped Active EMI Filter for Single- and Three-Phase AC-DC Applications

A compact and efficient design of the electromagnetic interference (EMI) filter is critical to reach the full benefits of electrification in highly constrained operating environments, such as on-board chargers (OBCs) for battery electric vehicles (BEVs). Through miniaturization of toroidal-cored common-mode (CM)chokes, an active EMI filter (AEF) circuit for CM noise attenuation can substantially increase thegravimetric and volumetric power densities of the EMI filter implementation. This paper examines small-signal stability by deriving loop-gain expressions for a feedback-type, voltage-sense, current-inject (FB-VSCI) AEF circuit implemented using an integrated-circuit (IC) approach. The formulated expressionsare subsequently confirmed by simulations and experimental validation of a two-stage EMI filter designsuitable for a 22-kW universal-input OBC.