Effective, small, and inexpensive common-mode EMI reduction using inverse secondary current cancellation

Abstract

This paper describes implementation of a small, cheap and highly effective (10-20dB) EMI reduction method attacking the 150kHz to 3MHz range of Conducted EMI from the most notorious source. It is particularly effective where 2-wire AC input (no AC ground) is used, if 50-60Hz output leakage current is an issue, or improvement to space, cost and efficiency is desired. It reduces or eliminates traditional brute-force filtering, transformer shielding and other “conventional” methods.