A Three-Level Boost Converter With Fully State-Based Phase Selection Technique for High-Speed VCF Calibration and Smooth Mode Transition Seung-Ju Lee

Abstract

In this article, a three-level current-mode boost con- verter with a fully state-based phase selection (FSPS) technique is presented. The proposed FSPS technique selects the operation phase adaptively to ensure the voltage across the flying capacitor (VCF) to VO/2 and changes the operation mode of a three-level boost converter (3L-BST). It enables the flying capacitor to be charged or discharged consecutively at the same duties every switching period and the operation mode to be changed smoothly. Therefore, 3L-BST improves the VCF calibration speed with the stable startup and removes the sub-harmonic oscillation of the inductor current caused by the VCF calibration, and the output voltage fluctuation is alleviated in the mode transition region. In addition, to compensate the stability of both valley and peak current-mode control for a wide output voltage range, the proposed FSPS technique adopts the adaptive slope generator (ASG) of which the slope can be changed from negative to positive. This work, fabricated in a 0.18-µm bipolar-CMOS- DMOS (BCD) process, occupies an area of 5.51 mm 2. The peak efficiency of the proposed 3L-BST is 95.3%, with an input range of 2–6 V , an output range of 5–32 V , and a 0.5-A maximum load current. The inductor current ripples are 1.45× smaller than prior VCF calibration techniques. The total startup time is 490 µs.