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

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 × 10 mm2 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. key words: LCD, PDLC, 1-pixel, low power, capacitor