OLED Pixel Circuit Threshold Voltage Sensing Accuracy
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Solution Overview
Problem
The accuracy of sensing threshold voltage in organic light emitting diode display devices is compromised due to high-frequency driving and increased size and resolution, leading to variations in luminance and RC delay, which affects the precision of threshold voltage sensing.
Innovation Solution
An organic light emitting diode display device with a specific pixel structure comprising a driving TFT, an organic light emitting diode, and additional TFTs and capacitors, where a reference voltage is used to compensate for the threshold voltage, allowing for improved sensing accuracy by inverting control signals and utilizing capacitors to stabilize node voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high frequency driving is used to implement 3D image or improve image quality, then image quality is improved, but accuracy of sensing threshold voltage gets lower due to shortened sensing period
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage sensing before the high-frequency image display period. The sensing operation is completed in advance during a dedicated sensing period, allowing the system to acquire accurate threshold voltage data before the high-frequency driving begins, thus resolving the conflict between high-frequency image quality and sensing accuracy.
Solution Approach 2:
The patent segments the display operation into distinct phases: a sensing period for acquiring threshold voltage data and a display period for high-frequency image output. This temporal segmentation allows both functions to operate independently with optimal parameters - accurate sensing during the dedicated period and high-frequency driving during the display period, eliminating the interference between them.
2Illumination intensity
If display device size and resolution are increased, then display quality is improved, but line resistance increases and RC delay occurs, shortening sensing period
Solution Approach 1:
The patent performs threshold voltage sensing as a preliminary action before the high-frequency display period. By completing the sensing operation in advance during a dedicated sensing period, the system ensures that accurate threshold voltage data is acquired before RC delay effects during high-frequency driving can interfere with the sensing process, thus maintaining sensing accuracy in high-resolution displays.
Solution Approach 2:
The patent divides the operational timeline into separate sensing and display periods. This segmentation isolates the sensing operation from the high-frequency display operation, allowing the sensing period to be optimized for accuracy while the display period handles high-resolution image output, preventing RC delay during display from affecting sensing precision.
3Stability of the object's composition
If threshold voltage compensation is implemented, then luminance uniformity is improved, but device complexity increases due to additional TFTs and capacitors
Solution Approach 1:
The patent implements multi-functionality by using the additional TFTs and capacitors to serve dual purposes: they are essential for the threshold voltage sensing operation and simultaneously provide compensation for threshold voltage variations during display. The sensing circuit components also function as compensation elements, eliminating the need for separate compensation circuitry and reducing overall device complexity.
Solution Approach 2:
The patent merges the sensing function and compensation function into a unified circuit configuration. The additional TFTs and capacitors that enable threshold voltage sensing also serve as the compensation mechanism for luminance uniformity. By combining these functions, the patent avoids adding separate compensation circuits, thus improving luminance uniformity without proportionally increasing device complexity.
Data Source
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AI summary
This embodiments herein relate to an organic light emitting diode display device comprising: a display panel configured to include a plurality of pixels disposed in a matrix form, wherein each of the pixels including: a driving TFT, an organic light emitting diode, a control circuit including first to fourth TFTs, capacitors. The embodiments described herein may improve accuracy of sensing a threshold voltage of the driving TFT even though the organic light emitting diode display device drives high frequency such as 240Hz because sensing periods are long enough to sense the threshold voltage of the driving TFT. Also, the embodiments described herein may compensate a drop of a high potential voltage due to compensating the current between a drain electrode and a source electrode of the driving TFT by using the high potential voltage dropped.