LTPS Pixel Circuit for Uniform High-Brightness Display
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Low temperature poly-silicon thin-film transistor (LTPS TFT) display devices suffer from uneven electrical characteristics due to varying crystal grain sizes, leading to inconsistent display quality, especially in high-brightness environments where wearable devices need enhanced luminance to maintain clear visibility.
Innovation Solution
A pixel circuit design comprising a driving transistor, compensation circuit, writing circuit, emission control circuit, and reset circuit, which adjusts data signals to compensate for threshold voltage variations and increase driving current, enabling operation in both normal and high-brightness modes with adjustable luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If excimer laser annealing is used to manufacture LTPS TFT, then high carrier mobility and small size are achieved, but uneven crystal grain sizes cause different threshold voltages at different locations
Solution Approach 1:
The patent applies preliminary action by compensating for threshold voltage variations before the display device operates. The compensation circuit pre-adjusts the gate voltage of the driving transistor based on the actual threshold voltage at each location, ensuring uniform display quality before any unevenness becomes visible to the user.
Solution Approach 2:
The patent changes the electrical parameters (voltages and currents) in the pixel circuit to compensate for threshold voltage variations. By adjusting the gate voltage, emission voltage, and data signals dynamically, the system maintains consistent display performance across different locations despite variations in transistor characteristics.
2Area of moving object
If LTPS TFT is used for high resolution display, then small pixel size is achieved, but threshold voltage variations cause uneven display pictures
Solution Approach 1:
The patent applies local quality by providing location-specific compensation for each pixel or group of pixels. The compensation circuit adjusts parameters locally based on the actual threshold voltage at that specific location, rather than using a uniform approach across the entire display, thereby maintaining display uniformity despite small pixel sizes.
Solution Approach 2:
The compensation for threshold voltage variations is performed in advance during the initialization phase, before the display operates. This preliminary adjustment ensures that each pixel starts with the correct voltage levels to compensate for manufacturing variations, preventing uneven display from the outset.
3Illumination intensity
If higher driving current is applied to increase brightness, then luminance is improved, but power consumption increases
Solution Approach 1:
The patent applies dynamics by making the emission voltage and driving current adjustable based on the desired brightness level. The system can dynamically switch between normal mode and high-brightness mode, optimizing the balance between luminance and power consumption according to the actual display requirements and environmental conditions.
Solution Approach 2:
The patent changes the electrical parameters (emission voltage and data signal levels) to control the driving current through the light emitting element. By adjusting these parameters, the system can achieve different brightness levels while managing power consumption, rather than always operating at maximum current.
Data Source
AI summary
A high-brightness display device includes a plurality of pixel circuits and a driving line. The driving line is configured to provide a first data signal and a second data signal to a column of pixel circuits of the plurality of pixel circuits. When the high-brightness display device is operated in a normal mode, the first data signal is a DC signal and the second data signal is an AC signal, and a driving current of a pixel circuit of the column of pixel circuits has a first maximum current value. When the high-brightness display device is operated in a high-brightness mode, the first data signal and the second data signal are both the AC signals, and the driving current of the pixel circuit have a second maximum current value. The second maximum current value is larger than the first maximum current value.