Study on periodic and non periodic frequency modulation techniques for EMI suppression in SMPS

Switching Mode Power Supplies (SMPS) usually emit Electromagnetic Interferences (EMI) at switching frequency and its harmonics. There are many different methods to reduce EMI interferences made by switching converters. In this paper different kinds of spread spectrum EMI reduction methods have been tested. Unlike traditional proper tuned filters used for this purpose, PWFM technique is a reliable and cheap method which could be used in small high frequency converters using in communication circuits such as cellular phones and etc.