It　is　known　to　all　that　parasitic　capacitances　in　a　transformer　is　very　critical　for　EMI　CM　noise.　Generally,　Faraday　shielding　connected　at　primary　minus　is　used　in　most　transformers　to　shield　the　induced　charge　and　block　the　CM　noise　path.　Based　on　CM　noise　balance　concept,　a　novel　noise　balance　configuration　by　adding　an　extra　capacitor　between　shielding　foil　and　primary　minus　was　proposed　to　reduce　the　CM　noise　by　adjusting　electrical　potential　in　the　shielding　foil,　so　that　to　integrate　the　enhanced　EMI　filter　function　to　the　transformer.　CM　noise　model　had　been　built　and　analyzed　in　detail.　The　effect　of　the　novel　CM　noise　reduction　technique　had　been　verified　by　experiment.　©2009　IEEE.