A new single inductor bipolar multi-output (SIBMO) DC-DC converter driven by constant on-time with improved performance

Abstract

This study is dedicated to design and realization of a new single inductor bipolar multi-output (SIBMO) DC-DC converter with performance improvement. A bandgap is first designed to offer a stable input bias with capability to work against inevitable input voltage variations for avoiding possible p-n breakdowns. A new drive technique based on constant on-time (COT) is developed for the designed SIBMO with assistance from level shifters and zero current detection circuits to drive MOS devices. The designed circuit is capable of boosting input voltage 2.8 V to four bipolar outputs of +6, -6, +12 and -12 V. The COT proposed herein adopts a new technique of time multiplexing to offer stable multi-outputs with an off-chip inductor for fast switchings. This new COT is different from the conventional pulse width modulation which usually operates with fixed frequencies. The COT is particularly favorable in regards of crossing regulation and high transfer efficiency in cases of unbalanced loads. The proposed SIBMO and COT are applicable to drive systems of organic light-emitting diodes, optical sensors, and portable electronic devices, displays, etc. The designed on-chip SIBMO and COT are fabricated via the TSMC 0.25 A mu m high-voltage CMOS process. Experimental results clearly show the capability of the designed SIBMO chip to offer four bipolar, stabilized output voltages with a total power consumption minimized to 320 mW and the switching frequency varying from 650 to 500 kHz. Most importantly, the maximum efficiency reaches 83.1 %.