Display Apparatus Compensation Circuit for Luminance Uniformity
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Solution Overview
Problem
Active-matrix organic EL display apparatuses face issues with luminance unevenness and increased power consumption due to threshold voltage fluctuations and current dispersion among driving transistors, which hinder the efficient display of high-quality images, especially in dark image scenarios.
Innovation Solution
The implementation of an image signal compensation circuit with a compensation memory, comparison circuit, and arithmetic circuit that compensates for threshold voltage and current dispersion among driving transistors, using capacitors and transistors to optimize current flow and reduce luminance unevenness while minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a compensation circuit is used to reduce luminance unevenness, then image quality is improved, but power consumption increases
Solution Approach 1:
The patent implements a conditional compensation mechanism where the compensation circuit is activated only when luminance unevenness exceeds a predetermined threshold. The determination circuit dynamically assesses the need for compensation by comparing actual luminance values against reference values, enabling the system to switch between compensation and non-compensation modes based on real-time display conditions, thus reducing unnecessary power consumption while maintaining image quality when needed
Solution Approach 2:
The patent adjusts the compensation operation based on image characteristics by analyzing the standard deviation of luminance values. When the standard deviation indicates significant luminance unevenness, the compensation circuit is activated; otherwise, it remains inactive. This parameter-based control allows the system to adapt its power consumption and compensation level according to the actual display content
2Ease of manufacture
If TFT is used for driving transistor, then manufacturing cost is reduced, but threshold voltage fluctuation increases
Solution Approach 1:
The patent incorporates a determination circuit that continuously monitors luminance values and compares them against reference values to detect threshold voltage fluctuations in TFTs. When fluctuations exceed a predetermined threshold, the system activates the compensation circuit to correct the luminance unevenness. This feedback mechanism allows the use of cost-effective TFTs while maintaining display quality through automated compensation when needed
Solution Approach 2:
The pixel circuit includes self-compensation capabilities through compensation capacitors that automatically adjust for threshold voltage variations. The determination circuit and compensation circuit work together to enable the display apparatus to self-correct luminance unevenness caused by TFT characteristics, reducing the need for high-precision (and higher cost) transistor manufacturing
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 solution enables the display of high-quality images with reduced luminance unevenness and lower power consumption, particularly in dark image scenarios, by effectively compensating for threshold voltage and current dispersion, thereby maintaining the low power consumption advantage of organic EL devices.
Implementation Method 1
Each of the pixel circuits has a compensation capacitor which compensates a threshold voltage of the driving transistor
Implementation Method 2
An organic EL (electroluminescence) display apparatus has a large number of arrayed self-luminous organic EL devices
Data Source
AI summary
A display apparatus has an image display unit having a plurality of arrayed pixel circuits, and an image signal compensation circuit compensating an image signal and outputs the compensated signal to the image display unit. Each of the pixel circuits has a compensating capacitor which compensates the threshold voltage of the driving transistor. The image signal compensation circuit has a compensation memory storing a compensation data for compensating the current variation of the driving transistors, a first comparison circuit which compares the image signal and first threshold value, and an arithmetic circuit compensating the image signal. When the image signal has a luminance larger than the threshold value, the compensation is performed.