Finding poles and zeroes of an SMPS output filter

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SiCEngineer

Joined May 22, 2019
81
Hello,

I am wondering what is the easiest way to find the transfer function/poles and zeroes of an SMPS output filter which is not just a simple LC, so that I can calculate the required compensation for the control system. Is it best to do this mathematically, or can we do it in LTSpice with bode plots?

I will attach an image of the filter. It seems to be a cascade of an RC into an CLC pi-filter. It is to my understanding that the poles/zeroes are only a function of the passive components and their ESR? Therefore, do the additional resistors across the inductor and on the input/output actually contribute anything to the ac response?

I have available to me the passive values however have no clue how to derive the poles and zeroes or how to identify them in LTSpice.
 

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