Designing electromagnetic interference filter for switched mode power supply

Abstract

A switched mode power supply (SMPS) converts alternating current (AC) power to low voltage direct current (DC) power for the electronic circuits in an electronic product. SMPS is widely used in nearly all electronic products due to its excellent conversion efficiency despite its design complexity. However, the high frequency switching technique adopted in the power conversion process generates significant electromagnetic interference (EMI) on the AC power mains. In view of its EMI issue, every SMPS must comply with the relevant mandatory EMI regulatory standard before it can be sold in the market. To meet the required EMI limit in the standard, an EMI filter is a necessity. This dissertation focuses on the design of an EMI filter so that the SMPS can comply with the relevant regulatory conducted emission limit. The design will also be verified through conducted emission measurement in accordance with the recommended setup given in the standard.