Pixel Circuit Compensation for AMOLED Touch Integration
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Solution Overview
Problem
Existing OLED displays face issues with non-uniformity in threshold voltages of driving thin film transistors (TFTs), leading to variance in driving currents and affecting display uniformity, and lack integration of touch functionality with AMOLED technology.
Innovation Solution
A pixel circuit with a compensation unit to adjust for threshold voltage variations in TFTs, combined with a touch detection sub-circuit using capacitance or photosensitive principles, ensuring uniform OLED operation and integrating touch functionality within the AMOLED display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a 2T1C driving circuit is used to drive OLED, then the circuit structure is simple and cost is reduced, but threshold voltage non-uniformity of driving TFTs causes current variance and affects display uniformity
Solution Approach 1:
The pixel circuit is divided into separate functional modules: a driving sub-circuit (with driving TFT and storage capacitor) for current control and a touch detection sub-circuit (with sensing electrode and detection TFT) for touch input. This segmentation allows independent optimization of each function, enabling threshold voltage compensation in the driving circuit while maintaining overall simplicity.
Solution Approach 2:
The pixel circuit is designed to perform multiple functions: display driving (current control for OLED) and touch detection (capacitive or photosensitive touch sensing). By integrating these functions into a single pixel circuit structure, the patent achieves both simplified overall design and improved display uniformity through dedicated compensation mechanisms.
2Use of energy by moving object
If OLED is used as display element, then power consumption is reduced and response speed is improved, but threshold voltage variations in driving TFTs cause current non-uniformity
Solution Approach 1:
A storage capacitor is connected to the gate of the driving TFT to pre-store the gate voltage. This preliminary action maintains stable gate voltage despite threshold voltage variations, ensuring uniform driving current to OLED. The capacitor compensates for voltage drops and maintains consistent current output across different pixels.
Solution Approach 2:
The circuit incorporates feedback mechanisms where the storage capacitor voltage is adjusted based on detected threshold voltage variations. By monitoring and compensating for TFT threshold voltage drift, the system maintains uniform current distribution across OLED pixels, ensuring display consistency while preserving OLED's low power consumption benefits.
3Length of stationary object
If touch electrodes are embedded inside display screen (In-Cell Touch), then overall thickness is reduced and production cost is reduced, but integration with AMOLED requires complex pixel circuit design
Solution Approach 1:
The touch detection sub-circuit is merged with the display driving sub-circuit within the same pixel structure. The sensing electrode is integrated into the pixel circuit, sharing common elements like scan lines and control signals. This merging achieves thin profile and cost reduction while managing complexity through unified circuit architecture.
Solution Approach 2:
The pixel circuit is designed as a multi-functional unit that simultaneously handles display driving and touch detection. By making the pixel circuit universal, the patent avoids separate complex circuits for each function, thereby reducing overall device complexity despite the integrated nature of In-Cell Touch with AMOLED.
Data Source
AI summary
A pixel circuit and a driving method thereof, an array substrate including the pixel circuit and a display apparatus thereof are provided. The pixel circuit comprising a display driving sub-circuit (200) and a touch detection sub-circuit (210), wherein the display driving sub-circuit (200) is configured to drive a display element to emit light under controls of the first scan line (SCAN1), the second scan line (SCAN2), the third scan line (SCAN3), the data line (DATA) and the light emitting control line (EM); and the touch detection sub-circuit (210) is configured to detect a touch action and generate a sense signal under controls of the second scan line (SCAN2), the third scan line (SCAN3) and the data line (DATA). The effect due to variances in a threshold voltages of driving thin film transistors can be eliminated by compensation, and an integration of a touch function and an AMOLED is achieved.