Bi-Stability Phenomenon in Constant On-Time Controlled Buck Converter With Small Output Capacitor ESR

Abstract

This paper reports the finding of bi-stability phenomenon in a constant on-time (COT) controlled buck converter with a small output capacitor equivalent series resistance (ESR). In the previously published literatures, it has been reported that the COT controlled buck converter with a small output capacitor ESR operates in the reduced-frequency periodic oscillation state. However, it is newly validated by numerical simulations that for some specified initial states, such a buck converter with the same circuit parameters can operate in a chaotic oscillation state as well, reflecting the existence of bi-stable oscillation states. Based on the piecewise continuous model of COT controlled buck converter, the bi-stability phenomenon associated with two sets of initial states is revealed by numerical simulations and verified by PSIM circuit simulations. Consequently, when a small output capacitor ESR is used, the coexisting attractors' behavior of two bi-stable oscillation states appears in such a COT controlled buck converter, leading to the emergence of bi-stability phenomenon.

Keywords

• Constant on-time (COT) control
• buck converter
• equivalent series resistance (ESR)
• bi-stability