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

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_OUT = 2.5 A 30-mΩ NMOS power stage. Measured accuracy of the detection is in order of <;15 mA.