A Hybrid Buck-or-Boost Converter for Fast-Transient and Wide-Voltage-Range Applications With Continuous Output Delivery Current

Abstract

This article proposes a hybrid right-half-plane (RHP) zero free buck-or-boost converter designed for applications requiring wide-range input/output voltage levels, fast dynamic voltage scaling (DVS), and load transient responses. The converter operates with a Li-ion battery input voltage range of 2.7–4.2 V and an output voltage range of sub-1 to 6 V. To ensure continuous output delivery current when the voltage conversion ratio (CR) exceeds 2, a dual flying capacitor mode is proposed, which reduces output voltage ripple and alleviates current capacity limitations. Additionally, techniques for reference tracking are introduced to enhance tracking speed and ensure transient reliability. This article also includes dc and ac analysis of the proposed converter, the driver design, the mode transition design, and the start-up process. The chip measurement results show the voltage CR is approximately 0.21–2.22 with a peak efficiency of 97.3%. DVS rates of 1.13– $2.33~{\mu }$ s/V are obtained with the help of assisted time for enhancement. Given an input voltage of 3.7 V and output voltage of 2.5 and 5 V, with step-up and step-down load current ranging from 50 to 800 mA in less than 200 ns, the settling time in both buck and boost modes is around $6~{\mu }$ s.