Small-Signal Analysis and Design of Constant On-Time Controlled Buck Converters With Duty-Cycle-Independent Quality Factors
Wen-Chin Liu, Ching-Hsiang Cheng, Patrick P. Mercier, Chris Mı
Abstract
This paper 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q$</tex-math></inline-formula> -value. A constant <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q$</tex-math></inline-formula> -value circuit based on the proposed strategy is then constructed and incorporated with a baseline ultra-fast transient constant on-time (UFTCOT) 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.