Liquid Crystal Display Driving with Position-Dependent Pre-Charge
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Solution Overview
Problem
Liquid crystal display devices experience irregularities in display due to flicker and grainy screen issues caused by uneven current leakage during dot-sequential driving, which are not adequately addressed by increasing frame frequency or using AC voltage driving.
Innovation Solution
A liquid crystal display device with a pixel array unit, scan lines, and data lines, where the pre-charge voltage and scan signal voltage are varied according to the position of pixels in the array to control the conductive state of pixel transistors, reducing current leakage and its visual effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If dot-sequential driving is performed with inverted common electrode voltage, then power consumption is reduced, but current leakage varies by pixel position causing flicker and grainy screen
Solution Approach 1:
The patent applies local quality by differentiating the pre-charge voltage based on the row position of pixels. Different row groups receive different pre-charge voltages (e.g., first pre-charge voltage for odd rows, second pre-charge voltage for even rows) to compensate for position-dependent current leakage variations, thereby achieving uniform display characteristics across the entire panel while maintaining AC driving efficiency
2Reliability
If frame frequency is increased to reduce current leakage time, then flicker is reduced, but power consumption increases
Solution Approach 1:
The patent applies preliminary action by applying a pre-charge voltage to data lines before the actual video signal is written. This pre-charge phase prepares the data lines to reduce subsequent current leakage during the video signal holding period, effectively reducing the need for higher frame rates and lowering overall power consumption while maintaining display uniformity
Data Source
AI summary
A liquid crystal display device includes: a pixel array unit in which pixels including a liquid crystal cell are arranged in a matrix; scan lines; common wiring; and data lines, in which each of the pixels includes a pixel transistor connecting the data line and the pixel electrode, a conductive state/a non-conductive state of the pixel transistor is controlled by a scan signal voltage applied to the scan line, a signal voltage whose polarity is inverted in regular cycles is supplied to the common wiring, and at least one of a pre-charge voltage supplied to the data line prior to writing of a video signal voltage or a scan signal voltage supplied to the scan line when no pixel is selected is supplied so as to vary in accordance with the position at which the pixels are selected row by row in the pixel array unit.