The Active EMI Filter for Suppressing Common-Mode Noise in Bridge-less PFC Converter System

This paper proposes an active electromagnetic interference (EMI) filter to suppress the common-mode voltage which is generated by a bridge-less power-factor-correction (PFC) converter. The active EMI filter topology is based on an active noise canceller of both the feed-forward voltage detection and voltage injection methods. In this paper, the common-mode equivalent circuit model of the active noise canceller including a bridge-less PFC converter have been developed and the transfer function of an open-loop model based on the equivalent circuit model is derived in order to ensure the stability. The derived transfer function is useful in choosing the appropriate components value in order to achieve stability and noise attenuation performance in design of active EMI filter. Finaly, the proposed method has been analyzed theoretically and also verified in experiment.