Control design for integrated switch-mode power supplies: a new challenge?

Abstract

Hard switching DC/DC converters have been studied for decades. Many control techniques have been reported, and textbooks detail so-called classical control design methods. The buck converter is known as a simple topology of satisfying stability. However the monolithic integration of a buck converter including the control system leads to a possible non-stable converter in case of large load transient. More generally it is difficult to certify the accuracy of the control system. Integrated switch-mode power supplies needs to be investigated focusing control design issues. Global efficiency dictates to limit the budgets in biasing current of control loops, hence limits their bandwidth. Among others, this latter limitation renders the classical control design methods non satisfying. The paper investigates the control design challenge related to integration of switch-mode power supplies (SMPSs). Applications are discussed from simulation point-of-view. Particularly a trade-off must be set between control accuracy and performances on load transients. As it is not possible to specify the worst-case load transient, classical control design methods do not offer satisfying results. Alternative control design methods are investigated. Sensitivity transfer functions are introduced and an application method is detailed. Hybrid system methods are also investigated and their application is discussed. The design of integrated SMPSs requires adequate modifications of CAE-tools and design flows.