Automatic EMI Measurement and Filter Design System for Telecom Power Supplies

Tests for compliance with conducted emission limits are usually carried out during the electrical product design process. Electromagnetic interference (EMI) filters are widely used for filtering excessive conducted emissions on a power cord. In this paper, a personal computer (PC)-based automatic EMI measurement and filter design system for telecom power supplies is proposed. The common-mode (CM) and differential-mode (DM) emissions in the live or the neutral line can be measured and recorded separately. The trial-and-error guesswork in selecting the filter components can be minimized by the proposed automatic filter design system. In other words, the EMI suppression effort is greatly reduced by the fast PC computing speed and the man-machine interface. The developed system can be an effective noise diagnosis and filter design tool for EMI engineers.