A 12-to-1–1.8-V Hybrid DC-DC Converter With a Charge Converging Phase for Inductor Current Reduction

Abstract

This article presents a 12-V-input and 1–1.8-V-output hybrid buck converter featuring a charge converging phase (CCP-HB). During this phase, charges from multiple paths converge into one flying capacitor, increasing the charge accumulated on it. Such charge gets transferred to the output in parallel with the inductor during the other phase, and thus, the average inductor current is reduced to consistently less than half of the load current across the entire voltage conversion ratio (VCR) range. This approach significantly reduces dc resistance (DCR) conduction loss and mitigates the reliance on a bulky inductor. Besides, a stacked switched-capacitor network (SCN) is adopted between the input and the output to reduce voltage stress on power switches for better efficiency. The converter was fabricated in a 0.18- $\mu $ m BCD process, utilizing only 5- and 1.8-V NMOS as power switches. Measurement results show that the converter achieves a peak efficiency of 95.4% with a small DCR of 10.5 m $\Omega $ . Moreover, the CCP enables the use of a compact inductor as small as the 2016 series ( $2{\times }1.6{\times }1$ mm3) with a large DCR of 57 m $\Omega $ and a low saturation current of 3.6 A to deliver a full load of up to 5 A. The converter still maintains a peak efficiency of 94.7%, and the current density of total passive volume is up to 685 A/cm3.