High-efficiency peak-current-control non-inverting buck-boost converter using mode selection for single Ni-MH cell battery operation

Abstract

A peak-current-controlled non-inverting buck-boost converter with a mode selection scheme for a single Ni-MH cell battery operation is proposed. In order to extend the run time of a Ni-MH battery, the proposed mode selection circuit automatically puts the converter into a buck, boost, or buck-boost mode by comparing the input and output voltages. Among the three modes, the operation range of the buck-boost mode is designed to be minimized since its power conversion efficiency is lowest. The proposed mode selection circuit is applicable to peak-current control and variable output voltage converters. The frequency compensation circuit is designed to guarantee a sufficient phase margin for all three modes. The proposed converter is implemented in a 0.18 mu m CMOS technology, and the chip area is 2.31 mm(2). The experimental results show that the maximum power conversion efficiency of the proposed non-inverting buck-boost converter is enhanced to 88 % from 76 % which is that of the conventional non-inverting buck-boost converter.