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Ripple Filter Damping Techniques

Question asked by Kentxu on Jun 19, 2017
Latest reply on Jul 20, 2017 by JamesYea

Found this very useful article by Kevin M. Tompsett on damping of a PSU output filter:

http://www.analog.com/media/en/technical-documentation/technical-articles/Designing-Second-Stage-Output-Filters-for-Swit… 

In Fig 4 there are 3 techniques shown to damp oscillation in the output C-L-C pi filter:

1. Resistor across the inductor

2. RC load on input

3. RC load on output

I can understand how techniques no. 1 & 3 work as they are loading the output of the filter to damp the oscillation, but I do not understand how no. 2 works. How can a RC load on the input of the filter stop oscillations on the output? It seems to me that the output LC can still resonate.

 

Any clarification of how technique no. 2 works would be well appreciated!

 

Thanks, Ken

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