Achieving Wide Voltage-Conversion-Ratio and Reduced Power Losses for High Efficiency with EVCR Buck Converter for a 1.8 V Power Rail

Abstract

This paper proposes an extended voltage-conversion-ratio buck converter with a voltage-conversion-ratio (VCR) of up to 0.67. Unlike previous hybrid converters with a VCR limit of under 0.5, the proposed converter reliably supplies power to power rails lower than 1.8 V over the entire operating range of a Li-ion battery without requiring additional external components. In addition, it minimizes every power loss from the DC resistance of an inductor, the equivalent series resistance of the flying capacitor, and on-resistance of power switches. As a result, it achieves higher efficiency while supplying a stable 1.8 V output voltage for mobile applications. Additionally, because the proposed converter simply operates in two-phase mode in entire VCR range, it is simpler than previous works in which the controller changes their operation mode between two-phase mode and three-phase mode depending on the VCR. The chip was fabricated in a 250-nm CMOS process and obtained a peak efficiency of 97.93% at VIN = 3.3 V, VO = 1.8 V, and IO = 0.3 A.