An Approach Combined CPWM with Passive Filter for Reducing EMI in a Flyback Converter

Chaotic pulse width modulation(CPWM) was used in power electronic converters to reduce electromagnetic interference (EMI) in recent decades. However, the CPWM technique has a good effect on the higher frequency but less on the lower as expectation, to give a better EMI reduction under 5MHz, this article proposes a method that combined CPWM with a passive filter for reducing EMI in a flyback converter which is the most common topology used in switching mode power supply. Compared with traditional PWM, there is about 20dB reduction can be reached by the proposed method applied in a flyback converter with 100kHz, respectively. Moreover, traditional PWM and Chaotic PWM effects on ripple were also analyzed.