Two-Domains Control of a Buck Converter

Abstract

In the design of a power converter, the maximum output voltage transient under load change is one of the main drivers. The ECSS-E-ST-20C imposes specific requirements on the power quality of a regulated bus, which result most of the time in the use of a large capacitor bank to cope with the linear loop dynamics. Moreover, this sometimes results in slow dynamic response.In this paper a combined linear and non-linear control applied to a buck converter is proposed. This control technique enhances the transient performance with a faster recovery time and allows smaller output filter capacitors to be used. The proposed control is a combination of a linear control based on a conductance control principle, and a non-linear control, which intervenes only during transients. The latter is based on the detection of the output voltage variation and on the immediate application of maximum or minimum inductor current, as consequence of voltage undershoot or overshoot. Once the controlled output voltage is within the allowed range, the linear control takes back the voltage regulation control.The buck converter is chosen as a reference topology since most of the current solar array regulators (SARs) use a buck or super buck topology. Most Battery Discharge Regulators (BDRs) are also based on buckderived topologies.This concept can find application in the three-domain regulated bus control.