Use open loop analysis to model power converters with multiple feedback paths

Loop stability analysis usually starts from an open-loop Bode plot of the plant under study such as the power stage of a buck or a flyback converter. In this situation, the designer can extract phase and gain data within the frequency range of interest.

The designer's job is to identify a compensator structure, which will lead to the selected crossover frequency affected by the right phase margin. The final step requires the study of the total loop gain, the power plant and the compensator, showing that the poles/zeros placed on the compensator ensure stability once the loop is closed.

If this operation is rather straightforward with single loops, the operation becomes more complicated with converters implementing weighted feedback. This article capitalizes on the work done with loop stability analysis techniques and explores different ways to apply the them to power converters featuring multiple feedback paths.

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