Hybrid control approach for the output voltage regulation in buck type DC-DC converter

Buck converter is modelled as a hybrid automaton for the purpose of designing an appropriate control law to regulate its output voltage. The circuit when operated in continuous current mode is pulled into a limit cycle, specified by the regulation specifications, although the switching frequency varies with the load. On the other hand, under light-load conditions, the circuit is pulled into a fixed-frequency limit cycle in discontinuous current mode to satisfy the regulation criteria. Therefore, the controller design is generic in the sense that the required regulation is met throughout the operating range of the buck converter. The control problem is simplified as a guard selection problem and guards, denning the discrete states, are derived using a simple circuit theoretical approach, by imposing certain regulation and control constraints. Satisfactory operation of the buck converter under the proposed scheme is demonstrated using computer simulations and laboratory experiments. The suitability and simplicity of the proposed control scheme over a wide range of disturbances is highlighted.