A New Single Inductor Bipolar Multiple Output (SIBMO) On-Chip Boost Converter Using Ripple-based Constant On-time Control for LCD Drivers

Abstract

A constant on-time (COT) single-inductor bipolar multiple-output (SIBMO) on-chip boost converter is proposed for LCD drivers in this study. The converter is designed for biasing some analog and digital circuits fabricated on glass substrates for benefits of extending the life of LCD. These circuits on glass require bipolar high voltages for drive LCDs. The converter boosts the input of 2.8V to two positive outputs and two negative outputs, +12V, +6V,-12V and -6V, respectively. Different from the commonly-used pulse width modulation (PWM), the constant on-time (COT) is adopted herein by a dynamic charging algorithm whose frequency is adapted to the varied output voltage level, thus enjoying the merit of less circuit complexity and a smaller chip area. The COT is in this study further developed to a ripple-based one for achieving applicability even with unbalanced output loads with high efficiency. While total maximum output power is 260mw and the switching frequency varies from 500 kHz to 650 kHz, the maximum efficiency reaches 82.4%. The converter is fabricated by TSMC 0.25 mu m 1P3M high voltage CMOS technology for verification.