VCOM Adjustment Using Distributed Photodiodes for LCD Flicker
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Solution Overview
Problem
In liquid crystal display devices, flicker can vary in strength across the display plane due to wiring resistance and other factors, making it difficult to accurately adjust the common electrode voltage (VCOM) using a single photodiode for detection, which can lead to incomplete suppression of flicker.
Innovation Solution
A plurality of photodiodes are distributed across the display plane to measure light and flicker, with each connected to a storage capacitance to accumulate and compare charges, allowing for the adjustment of the VCOM voltage to minimize flicker across the entire panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single photodiode is used to detect flicker, then the device complexity is reduced, but the measurement precision of flicker across the display plane deteriorates
Solution Approach 1:
The display plane is segmented into multiple regions, with photodiodes strategically positioned in different areas (including dummy pixel areas) to detect flicker locally. This segmentation allows comprehensive coverage of the display plane while maintaining manageable device complexity through systematic arrangement of multiple detection points.
Solution Approach 2:
Multiple photodiode detection results are merged and processed together to determine the overall flicker characteristics of the display plane. By combining data from multiple locations, the system achieves comprehensive measurement precision while using a structured approach that balances device complexity.
2Measurement precision
If multiple photodiodes are distributed across the display plane, then the measurement precision of flicker is improved, but the device complexity increases
Solution Approach 1:
Different regions of the display plane are assigned different photodiode detection capabilities based on local flicker characteristics. Dummy pixel areas with specific photodiode arrangements are used to detect local flicker patterns, allowing optimized measurement precision in each region while managing overall device complexity through targeted rather than uniform distribution.
Solution Approach 2:
The detection system extends into the dummy pixel area dimension, utilizing spaces outside the main display area for photodiode placement. This dimensional expansion allows additional detection points without interfering with the visible display, improving measurement precision while minimizing impact on device complexity.
3Ease of manufacture
If dummy pixels are used for photodiode placement, then the ease of manufacture is improved, but the area available for display is reduced
Solution Approach 1:
Photodiodes are extracted from the main display area and placed in dummy pixel areas, separating the detection function from the display function. This extraction allows photodiodes to be integrated into non-display regions, improving ease of manufacture while preserving the full display area for image output.
Solution Approach 2:
The solution moves photodiode placement to the dummy pixel dimension, utilizing peripheral areas outside the active display region. This spatial reorganization enables photodiode integration without encroaching on the display area, simultaneously improving ease of manufacture and maintaining display area integrity.
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 enables more accurate and comprehensive adjustment of the VCOM voltage, reducing flicker and ensuring consistent image quality without increasing the device's thickness or part cost, by using TFT photodiodes on a TFT array substrate and arranging dummy pixels strategically.
Implementation Method 1
a photodiode is provided in each dummy pixel... for detecting the flicker to measure the amount of light
Implementation Method 2
each connected to a storage capacitance to accumulate and compare charges
Data Source
AI summary
A display device includes a display panel having pixels arranged in a matrix form, a driving circuit for outputting an analog voltage according to a video signal to the pixels through signal lines, a plurality of measuring circuits each for detecting the amount of transmitted light, a single totalizing circuit for totalizing the results of measurements made by the measuring circuits, and a control circuit for adjusting a potential on a common electrode of the display panel in accordance with the result of the totalization from the totalizing circuit. The results of measurements made by the plurality of measuring circuits are totalized by the single totalizing circuit.