Near Time-Optimal Transient Response in DC-DC Buck Converters Taking into Account the Inductor Current Limit

摘要

This paper analyzes the general problem ofinductor current limitation in the time-optimal load transientresponse of a DC-DC buck converter. The concept of currentlimited,time-optimal control (CL-TOC) is introduced andcompared to the previously reported unconstrained timeoptimalsolutions. A fundamental tradeoff between maximumallowed current overshoot and voltage recovery time isrecognized, and a set of design equations is developed whichprovide the engineer with the necessary analytical tools for thecontroller design. Furthermore, the minimum number ofswitching actions required to handle a generic current-limitedTOC is determined, leading to the formulation of a minimumswitchCL-TOC concept. Two distinct approaches for minimumswitchdigital CL-TOC are then introduced. The first method,which is an extension of a charge-balance approach, has theadvantage of achieving the time-optimal switching sequencewithout the need for a prior knowledge of the output filter LCparameters. The second approach implements a near CL-TOCemploying the switching surface concept and defining thecurrent limitation in the state-space. Simulation andexperimental results are provided to demonstrate theeffectiveness of the approaches.