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Design >> High-Power Design >> Current mode control model
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Message started by skywalker on Aug 29^th, 2005, 9:20am

Title: Current mode control model
Post by skywalker on Aug 29^th, 2005, 9:20am

Hello forum members,
I am having problems with modelling the power stage of an Off the shelf power supply which I am paralleling for redundancy and equal current sharing for uniform thermal stress on the individual power stages. Because I have no way of making frequency response measurements by AC singal injection I am having problems modeling the current mode controlled power stage of the POwer supply. Is there any ways I can develope a model without having to go through tedious frequency reponse analysis. The power supplies are current mode controlled Offline flyback power supplies.
Thanks in advance,
Ananth

Title: Re: Current mode control model
Post by Jess Chen on Aug 29^th, 2005, 3:31pm

That depends on what you mean by "tedious frequency response analysis". If you mean without having to derive state space averaged models, you have a couple of choices. You could try a comercial program specializing in SMPs, like Simplis for example (http://www.catena.uk.com/site/products/simplis.htm) but your schematic capture tool and libraries may or may not interface with it. You could try using SpectreRF's PAC analysis or perhaps a similar analysis of a harmonic balance simulator. Or you could try deducing the AC response from a brute force simulation of an impulse or step response.

However, I suspect the alternatives to state space averaging will require every bit as much work, if not more...at least the first time through anyway. You may still have to resort to state space averaging to check the new approach.

Any way you look at it, one way to simplify the analysis is to use a single converter model, scaled to represent the paralleled converters. As I recall doing this some years ago, as long as the stabilizing ramp is adequate there is no danger of unobservable RHP poles associated with oscillations between paralleled stages.