A Fully Adaptive-Ramp Ripple-Based Constant On-Time Buck Converter for
Stability Optimization in Wide-Range Operation
Abstract
The ripple-based constant on-time (RBCOT) buck converter with
small equivalent series resistance (ESR) of the output capacitor has the
potential issue of instability. The conventional fixed-ramp and
adaptive-ramp ripple compensation cannot keep the system stable under
different operational parameters (inductor, output capacitor, input
voltage, output voltage and on time). In this paper, a fully
adaptive-ramp ripple compensation technique is proposed which is based
on the finding that there is an inherent proportional relationship
between the slope of the critical stability compensation and the slope
of the output voltage at the beginning of on-time. This technique makes
the converter has robust adaptability and portability. A simple analog
circuitry, which can be easily integrated into an integrated circuit, is
provided to implement this technique. Experimental results are provided
to verify the proposed concept.
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