The System for the Reduction of Conducted Electromagnetic Interference Emission from Switching Power Supply

Abstract

Transmission of multimedia signals is commonly encountered in our daily life. Besides the researches in the base-band processing, transmission of multimedia signals is also an important branch. For transmission, the external power supply is inevitable, and the PC switching power supply produces the conducted emissions. These emissions usually can be reduced by using electromagnetic interference (EMI) filters. This research observes the conducted emissions from switching power supply by means of various EMI filters. The measured conducted emissions are unable to meet the limitation of FCC Part 15 Class B conducted by adopting commercial EMI filters, so we design EMI filters to reduce the conducted emissions produced by switching power supply in this study. We consider the common mode noise of switching power supply in order to simplify the design of EMI filter and use the power splitter to obtain the common mode noise. With suitable design of EMI filter, the conducted emissions of switching power supply will be reduced and accord with the limitation of FCC Part 15 Class B conducted.

EMI filter design based on the separated electromagnetic interference in switched mode power supplies

“…V att is noise attenuation, V axc is exceeded noise, and 6 dB is the correction factor [30]. The correction factor is added to the exceeded noise in order to ensure that noise is fully suppressed.…”