VA LCD Driving Circuit for Contrast Ratio and Aperture Ratio Trade-off
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Solution Overview
Problem
Vertical-aligned liquid crystal display (VA) mode LCDs face challenges in maintaining a high contrast ratio when viewed from the sides, as the luminance difference between gray levels diminishes, leading to poor image perception, and existing methods to improve this, such as capacitance combination of pixels, struggle with precise light transmittance control and aperture ratio deterioration.
Innovation Solution
An apparatus for driving a display device that includes a signal controller and a data driver, which alternately apply image data with different gray values to pixels, using gray voltage generators to produce voltages that invert polarity based on dot or frame inversion patterns, enhancing the contrast ratio by correcting image data to match the desired gamma curves and maintaining suitable color temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pixel division into two sub-pixels with capacitance combination is used to improve contrast ratio, then the contrast ratio is improved, but the aperture ratio deteriorates and light transmittance decreases
Solution Approach 1:
The pixel is divided into two sub-pixels (first and second sub-pixels) with different capacitance values. This segmentation allows differential voltage application where one sub-pixel receives the original data voltage while the other receives a voltage adjusted by the capacitance ratio, enabling gray scale differentiation without additional conductors that would reduce aperture ratio.
Solution Approach 2:
The invention changes the capacitance parameter of the sub-pixels by using different capacitance values (C1 and C2) in the two sub-pixels. This parameter change enables voltage differentiation through capacitance combination, allowing precise control of light transmittance for each sub-pixel while maintaining high aperture ratio since no additional conductors are needed.
2Reliability
If pixel division into two sub-pixels with capacitance combination is used to improve contrast ratio, then the contrast ratio is improved, but light transmittance is decreased due to voltage drop
Solution Approach 1:
The invention implements a feedback mechanism where the voltage applied to the second sub-pixel is adjusted based on the capacitance ratio between the two sub-pixels. The data voltage is modified according to the relationship C1/C2, ensuring that the voltage drop is precisely compensated and light transmittance is accurately controlled for each sub-pixel, preventing unnecessary transmittance loss.
3Adaptability or versatility
If openings or protrusions on field-generating electrodes are used to increase tilt angle, then viewing angle is widened, but contrast ratio becomes poor when viewed from lateral sides
Solution Approach 1:
The invention applies different capacitance values to different sub-pixels (C1 for first sub-pixel, C2 for second sub-pixel), creating local quality differences that enable differential voltage control. This allows each sub-pixel to be independently optimized for its light transmittance characteristics, maintaining high contrast ratio at lateral viewing angles while preserving the wide viewing angle achieved through the VA mode's molecular tilt structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the contrast ratio by precisely controlling light transmittance across pixels, reducing the luminance difference between gray levels, and maintaining a high aperture ratio, thereby enhancing the display's image quality and viewing angle.
Implementation Method 1
applying voltages to the field-generating electrodes to generate an electric field in the liquid crystal layer which aligns the liquid crystal molecules
Implementation Method 2
aligns the liquid crystal molecules of the liquid crystal layer to control the polarization of incident light
Implementation Method 3
When an electric field is applied, the liquid crystal molecules are tilted with respect to an axis normal to the panels
Implementation Method 4
so that polarization of light passing through the liquid crystal layer can be changed
Data Source
AI summary
An apparatus for driving a display device having a plurality of pixels includes a signal controller for selecting one data from a plurality of image data based on input image data, converting the selected data into output image data and outputting the output image data, and a data driver for converting the output image data from the signal controller into data voltages and applying the data voltages to the pixels. The mean value of front gammas of the first and second image data corresponds to the front gamma with respect to the input image data.