Chapter 18

The Math Behind the Electromagnetic Puzzle

This goes into Fourier series and the resulting frequency spectra of typical differential and common mode noise sources in switching power supplies. Detailed numerical examples are presented in each case, for a top to bottom filter design.

Fourier Series in Power Supplies

In previous chapters we have seen that differential and common mode noise (DM and CM) emissions are basically either voltage or current sources with arbitrary waveshapes. What they have in common is that they are repetitive, and therefore involve the basic switching frequency of the converter. When we design a filter to suppress these emissions, we have to be conscious of the fact that the efficacy of a filter is best characterized ...

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