A 24V-to-1V Triple Series-Capacitor Buck Converter With Low-Voltage Power Switches

Abstract

This brief introduces a 24V-to-1V hybrid converter with low-voltage power switches. By incorporating three flying capacitors in series with a two-phase switched-inductor, the proposed converter effectively functions as a 4.8V-to-1V converter. Thus, a high-voltage design is realized with low-voltage transistors known for their excellent figure of merit. As a result, the hybrid converter achieves an effective duty cycle five times higher and a better conversion efficiency compared with a double step-down converter (DSD) and a double series-capacitor converter (DSCBC) under identical power switch sizes and working conditions. The circuit is designed using a 0.15- $\mu $ m Bipolar-CMOS-DMOS (BCD) process to achieve a conversion from 24 V to 1 V. It can support a load current range of 200 mA to 6 A, with each sub-converter operating at a frequency of 1-MHz. Post-layout simulations show a peak power efficiency of 90.07% under a 2-A current load, with an efficiency of 85% even at a load of 6-A.