Modeling, Nonlinear and Robust control of DC-DC Switching Regulators

It is generally known that DC-DC switching regulators are highly nonlinear systems which are subjected to significant variation in the line voltage and load, uncertainty in the circuit parameters and perturbations in switching times. To assure stable operation and acceptable performance despite the disturbances and inevitable uncertainty associated with such systems, highly accurate regulation schemes must be devised. Indeed the routine application of most classical compensation techniques are severely limited when tight regulation measures have to be achieved. These considerations in conjunction with increasing demand for high quality DC-DC switching regulators has necessitated more systematic and precise methodologies in modeling and control design for such systems. The first step in the present thesis is to introduce various techniques for modeling switching regulators specifically models which account for parametric uncertainty and the nonlinear switching effects are intended. Using the models obtained in this fashion, the next step will be to apply nonlinear (input-output feedback linearization) and robust control (Mu-synthesis, Hinf and Kharitonov theorems) techniques to obtain controllers which guarantee satisfactory operation of the system under realistic operating conditions. The resulting controllers are shown to minimize the effect of disturbances and achieve acceptable regulation. The potential superiorities of these methods over classical methodologies are also discussed. At least, two approaches based on Mu-analysis and Kharitonov’s theorem are proposed for the analysis of switching regulators. Applications to practical circuits with buck and cuk converters are illustrated as case studies.