Switching Power Supplies A - Z, 2nd Edition

Chapter 16

Practical EMI Line Filters and Noise Sources in Power Supplies

This chapter discusses typical line filters for suppressing conducted EMI emanating from power supplies. It goes into IEC safety aspects when selecting Y-capacitors and also discusses ways to maximize the effectiveness of components used in line filters, including the pros and cons of ground chokes. It discusses the origins of differential-mode and common-mode noise in switching power supplies and describes their EMI spectra and equivalent LISN models. Ways to chassis-mount semiconductors with minimal impact on EMI are also discussed, along with efficacy of the LISN itself at different frequencies.

Part 1: Practical Line Filters

Having understood common-mode (CM) and differential-mode ...