Filter for e.g. switching power supply, has capacitor attached to secondary winding of transformer and selected such that resonant frequency of parallel resonant circuit is integral multiple of frequency of alternative current voltage

摘要

The filter has an inductor (3a) simultaneously provided as a primary winding (Lp) of a transformer (4), and a capacitor (C) attached to a secondary winding (Ls) of the transformer for forming a parallel resonant circuit. The capacitor is selected in such a manner that a resonant frequency of the parallel resonant circuit is an integral multiple of a frequency of an alternative current (AC) voltage. Performance of the parallel resonant circuit is adjusted by a parallel switched resistor (VDR) e.g. varistor, of the capacitor.