Design of Driving Waveform Based on Overdriving Voltage for Shortening Response Time in Electrowetting Displays

Wenjun Zeng,Liming Liu,Zichuan Yi,Xichen Zhou,Jianjun Yang,Guofu Zhou,Lingling Shui,Haoqiang Feng,Chongfu Zhang,Weibo Zeng,Simin Ma,Yiming Zhao

doi:10.3389/fphy.2021.642682

Abstract

A fast response speed of a pixel is important for electrowetting displays (EWDs). However, traditional driving waveforms of EWDs have the disadvantage of long response time. So, a driving waveform, which based on overdriving voltages and charge trapping theory, was proposed in this paper to shorten the response time of EWDs. The driving waveform was composed of an overdriving stage and a driving stage. Firstly, a simplified physical model was introduced to analyze the influence of driving voltages on the response time. Then, an overdriving voltage was applied in the overdriving stage to increase the respond speed of oil, and a target voltage was applied in the driving stage to obtain a target luminance. In addition, the effect of different overdriving voltages and overdriving time values on the response time was analyzed by charge trapping theory to achieve an optimal performance. Finally, the driving waveform was imported into an EWD for performance testing. Experimental results showed that the response time of the EWD can be shortened by 29.27% compared with a PWM driving waveform.

Highlights

A driving waveform, which based on overdriving voltages and charge trapping theory, was proposed in this paper to shorten the response time of Electrowetting displays (EWDs)
Electrowetting displays (EWDs) are a new type of electronic paper with fast response speed and extremely low energy consumption [1, 2], and it can compensate for the limitations of electrophoretic displays (EPDs) effectively in the two major performances of color and video [3–8]
A driving waveform, which based on overdriving voltages and charge trapping theory, was proposed to shorten the response time in EWDs

Summary

INTRODUCTION

Electrowetting displays (EWDs) are a new type of electronic paper with fast response speed and extremely low energy consumption [1, 2], and it can compensate for the limitations of electrophoretic displays (EPDs) effectively in the two major performances of color and video [3–8]. An EWD pixel is in an equilibrium state when no voltage is applied, and the colored oil forms a continuous spreading film between the hydrophobic insulating layer and the conductive liquid. The wettability of the colored oil on the hydrophobic insulating layer can be changed when a certain voltage is applied between a common electrode and a pixel electrode. Ions in conductive liquid would be pulled toward the hydrophobic insulating layer by electrostatic force when the driving voltage is applied to a pixel. The electrostatic force on the oil is reduced because of the charge trapping, which causes a decrease in the aperture ratio of EWDs. In addition, the relationship between the amount of trapped charges and the driving voltage has been determined by measuring surface potential at a liquid–solid interface in electrowetting-on-dielectrics (EWOD) [30]. Collected luminance data was transmitted to the computer, and Admesy software was used to record the luminance data in real time

Design of Driving Waveforms

CONCLUSION

Findings

DATA AVAILABILITY STATEMENT