Inductor Current Zero-Crossing Detector and CCM/DCM Boundary Detector for Integrated High-Current Switched-Mode DC–DC Converters

Abstract

This paper presents two circuits that allow us to accurately detect either the inductor current zero crossing, or the continuous/discontinous conduction modes boundary in the switched-mode dc-dc converters. Achieved detection accuracy allows us to improve the control and efficiency of the integrated high-output current converters, i.e., converters with low-resistance power switches. Detection is based on the voltage zero-cross detector, which provides ideally zero input-referred offset and very fast results. The concept of voltage polarity detector is based on the association of a dynamic current mirror and a simple autozero comparator. This paper describes the main concept of both circuits, aspects of the design allowing us to achieve high accuracy, and presents obtained results. Circuits' performances are demonstrated on the integrated step-down dc-dc converter with I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OUT</sub> = 2.5 A 30-mΩ NMOS power stage. Measured accuracy of the detection is in order of <;15 mA.