Stability of the fast voltage control loop in DC-DC converters

This paper describes a method for stability analysis and design of a fast voltage loop in DC-DC converters. The method is based on the Popov criterion, which unifies tools for nonlinear system analysis with frequency domain analysis tools used in linear systems. This study establishes sufficient conditions for absolute stability of time-varying control systems. The proposed conditions extend in a simple way the classical Popov criterion to time-varying memoryless nonlinearities, using previous results of Kharitonov. They are expressed in terms of Linear Matrix Inequalities (LMIs). The controller design procedure is demonstrated and experimentally verified on a DC-DC converter.