Small-Signal Analysis and Design of Constant On-Time Controlled Buck Converters With Duty-Cycle-Independent Quality Factors

This article presents a frequency-domain analysis that models the behavior of Constant-on-Time (COT)-controlled buck converters in wide-input–output-range scenarios. Based on this analysis, a design strategy is proposed to enable robust control with a duty-cycle-independent quality factor, also known as a constant $Q$ -value. A constant $Q$ -value circuit based on the proposed strategy is then constructed and incorporated with a baseline ultrafast transient COT control scheme to experimentally verify the system stability and optimal load transient response under wide input–output range scenarios. In addition, the design strategy is extended to other COT buck control schemes with simulation and calculation verifications.