Help with Common Mode Noise Calculations

[Comcokid]

Common mode noise arises in switching supplies from the capacitance of the power devices to the heatsink (surface area, insulator thickness and dielectric constant) and the switching speed and waveform of the power devices.

An engineer I work with has seen a book or article that works one through the calculations step-by-step to approximate the common mode noise of a design - but he can't find it again. Having this kind of logical design approach would then allows the filter choke and X & Y capacitors to be selected.

There's plenty of burte-force design approaches available (put in a filter and measure where you're at "cut-and-try"). But does anyone know of a book, article, or website that uses a systematic, logical approach to the estimation and design of filtering for common mode noise in a switching device/supply?

 

[treez]

http://www.edaboard.com/viewtopic.php?t=343274&highlight=conducted+emissions

.....that thread gives how to easily get a feel for common mode noise amplitude by quick measurement.

I am afraid there are a three dimensional, multitudinous labyrinth of ways that Common Mode Noise can be produced in an SMPS. Calculating it would be a waste of time. If you made a small mod, then you'd need to re-calculate.

powerint.com have some good tips on Common mode noise reduction in their PIDatabook (several MBs).

Good layout, flux bands, transformer shields, inductor placement...etc etc......some topologies are more susceptible to common mode noise than others.