Polysilicon TFT Display Driving Method for Luminance Uniformity
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Solution Overview
Problem
Organic light emitting devices with polysilicon TFTs face challenges in uniform semiconductor characteristic formation, leading to luminance deviations and picture quality degradation due to non-uniform current flow caused by varying threshold voltages, especially in hold-type displays where motion is discretely displayed, resulting in blurring effects.
Innovation Solution
A method of driving the display device using a sensing line, light-emitting element, and driving transistor, which involves calculating threshold voltages and electric field effect mobility to compensate for degradation and ensure uniform luminance, employing a control terminal, input terminal, and output terminal connected to a capacitor and ground voltage, and disconnecting them to sense voltages and calculate transition degrees of threshold voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polysilicon TFTs are used to achieve high electron mobility and low leakage current, then device performance is improved, but uniform formation of semiconductor characteristics becomes difficult leading to luminance deviation
Solution Approach 1:
The patent applies preliminary action by measuring and storing threshold voltage and mobility data for each pixel before actual display operation. This pre-characterization allows the system to compensate for manufacturing variations during operation, ensuring uniform luminance across all pixels despite polysilicon TFT uniformity issues.
Solution Approach 2:
The patent changes operational parameters by adjusting data voltages based on measured threshold voltage and mobility values for each pixel. This parameter adjustment compensates for manufacturing variations, allowing each pixel to operate at its optimal characteristics and achieve uniform luminance output.
2Stability of the object's composition
If hold-type display method is used to maintain fixed image for one frame, then image stability is achieved, but motion display becomes discrete causing blurring phenomenon
Solution Approach 1:
The patent implements periodic action by refreshing pixel data at multiple time points within each frame period. Instead of holding a single static value, the display updates pixel values periodically, creating multiple sustained periods that reduce motion blur while maintaining image stability during static periods.
Solution Approach 2:
The patent ensures continuity of useful action by maintaining pixel activation throughout the entire frame period through multiple sustained periods. This continuous operation, rather than discrete updates, eliminates motion blur while preserving image stability, as the pixel remains active and displaying information continuously.
3Duration of action of moving object
If threshold voltage of organic light emitting element degrades over time, then device aging occurs, but voltage change at drain side causes non-uniform current flow and picture quality degradation
Solution Approach 1:
The patent applies feedback by continuously monitoring pixel characteristics and adjusting data voltages based on measured threshold voltage and mobility values. This feedback mechanism compensates for threshold voltage degradation over time and ensures uniform current flow across all pixels, maintaining picture quality throughout the device lifetime.
Solution Approach 2:
The patent uses preliminary action by pre-measuring and storing threshold voltage and mobility data for each pixel. This pre-characterization creates a baseline that enables ongoing compensation for degradation, allowing the system to maintain uniform current flow and picture quality as the device ages.
Data Source
AI summary
A method of driving a display device including a sensing line, a light-emitting element, a capacitor, and a driving transistor, the driving transistor comprising a control terminal that is connected to the capacitor, an input terminal, and an output terminal, the method including: connecting the control terminal and the output terminal; connecting the control terminal and the output terminal to a ground voltage and then disconnecting the control terminal and the output terminal from the ground voltage; sensing a first voltage of the control terminal through the sensing line; and calculating a threshold voltage of the driving transistor based on the first voltage.