Low-Power Driving Technique for 1-Pixel Display Using an External Capacitor

Hiroyuki MANABE  Munekazu DATE  Hideaki TAKADA  Hiroshi INAMURA  

IEICE TRANSACTIONS on Electronics   Vol.E98-C   No.11   pp.1015-1022
Publication Date: 2015/11/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E98.C.1015
Type of Manuscript: INVITED PAPER (Special Section on Electronic Displays)
LCD,  PDLC,  1-pixel,  low power,  capacitor,  

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Liquid crystal displays (LCDs) are suitable as elements underlying wearable and ubiquitous computing thanks to their low power consumption. A technique that uses less power to drive 1-pixel LCDs is proposed. It harvests the charges on the LCD and stores them in an external capacitor for reuse when the polarity changes. A simulation shows that the charge reduction depends on the ratio of the capacitance of the external capacitor to that of the LCD and can reach 50%. An experiment on a prototype demonstrates an almost 30% reduction with large 1-pixel LCDs. With a small 10 × 10mm2 LCD, the overhead of the micro-controller matches the reduction so no improvement could be measured. Though the technique requires longer time for polarity reversal, we confirm that it does not significantly degrade visual quality.