Sensing TFT Dual-Function Control for OLED Emission Time
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Solution Overview
Problem
Display devices with organic light-emitting diodes (OLEDs) face brightness deviations due to non-uniform electrical characteristics of thin film transistors (TFTs), which affect image quality and require compensation to achieve high-density displays without increasing pixel size.
Innovation Solution
A display device utilizing a sensing thin film transistor (TFT) to control the emission time of OLEDs by applying a reference voltage lower than the threshold voltage, allowing for external compensation without additional light-emission control signals or transistors, thereby reducing the number of TFTs and improving pixel density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If external compensation scheme is applied to cure brightness deviation, then image quality is improved, but pixel size increases due to additional TFTs
Solution Approach 1:
The sensing TFT is made to perform dual functions: sensing the threshold voltage of the driving TFT and controlling the light-emission time of the OLED. By applying a reference voltage lower than the OLED threshold voltage during sensing operation, the same transistor controls both sensing and emission timing without requiring additional light-emission control TFTs, thus avoiding pixel size increase while maintaining brightness uniformity compensation
2Measurement precision
If additional light-emission control signals and TFTs are used to control OLED emission time, then emission control precision is improved, but device complexity increases
Solution Approach 1:
The sensing TFT is designed to control both the sensing operation and the light-emission time of the OLED by receiving different voltages (reference voltage during sensing, data voltage during emission). This eliminates the need for separate light-emission control TFTs and signals, reducing device complexity while maintaining precise emission control through the same transistor that performs sensing
Data Source
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AI summary
Various embodiments relate to a display device and a control method thereof, and more particularly, to a display device capable of controlling time section of light-emission of an OLED with utilization of a TFT (ST2) receiving a sensing signal (SENSE) when applying an external compensation pixel, and a control method of the display device. In accordance with an embodiment of the present invention, a display device may cure a brightness deviation and improve an image quality through a simple control scheme without drastic change of existing pixel structure.