Effects of X Capacitors on EMI Filter Effectiveness
Hung-I Hsieh; Jhong-Shu Li; Dan Chen
Industrial Electronics, IEEE Transactions on
Volume 55, Issue 2, Feb. 2008 Page(s):949 - 955
Digital Object Identifier 10.1109/TIE.2007.896258
Summary:The suppression mechanism of the differential-mode noise of an X capacitor in offline power supplies is, for the first time, attributed to two distinct concepts: 1) impedance mismatch (regarding a line impedance stabilization network or mains and the equivalent power supply noise source impedance) and 2) C(dv/dt) noise current balancing (to suppress mix-mode noise). The effectiveness of X capacitors is investigated with this theory, along with experimental supports. Understanding of the two aforementioned mechanisms gives better insight into filter effectiveness, which may lead to a more compact filter design.
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