OLED Pixel Circuit with Dual-Gate Transistor for Luminance Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic light emitting display devices face challenges in maintaining uniform luminance due to degradation of organic light emitting diodes and threshold voltage/mobility changes in driving transistors, which affect image quality and efficiency.
Innovation Solution
A pixel structure incorporating a precharge circuit, pixel circuit, sensing control circuit, and switching unit that allows for selective coupling of data lines to sensing lines and write control signals, enabling the sensing of degradation information and threshold voltage/mobility information of organic light emitting diodes and driving transistors, and adjusting operations accordingly to maintain uniform luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If organic light emitting diodes are used to display images, then fast response speed and low power consumption are achieved, but degradation of the organic light emitting diodes and threshold voltage/mobility changes in driving transistors cause non-uniform luminance
Solution Approach 1:
The patent applies preliminary action by performing sensing operations before the display operation. Specifically, during a sensing period before the display period, the circuit senses the threshold voltage or mobility of the driving transistor and stores this information. This allows the system to prepare compensation data in advance, which is then used during the display period to maintain uniform luminance despite transistor degradation. The dual-gate transistor structure enables this preliminary sensing action by allowing threshold voltage measurement before the actual display function is activated.
Solution Approach 2:
The patent implements feedback by using the sensed threshold voltage or mobility information to adjust and compensate for luminance variations. The sensing circuit measures the actual electrical characteristics of the driving transistor, and this measurement feedback is used to calculate compensation values that correct for degradation effects. The dual-gate transistor structure provides the feedback path by allowing the second gate to receive control signals that adjust the transistor's operation based on the sensed characteristics, thereby maintaining uniform luminance output across all pixels despite individual transistor variations and aging effects.
2Reliability
If sensing operations are performed to detect degradation information, then luminance uniformity is maintained, but additional circuit components and control signals are required
Solution Approach 1:
The patent applies universality by designing the dual-gate transistor to perform multiple functions: it serves as both the driving transistor for current control and as a sensing element for threshold voltage or mobility measurement. The same transistor structure is used for both display operation and sensing operation, eliminating the need for separate sensing transistors in each pixel. Additionally, the second gate of the dual-gate transistor can serve multiple purposes - receiving sensing control signals during the sensing period and display control signals during the display period, thereby reducing the number of separate control lines needed.
Solution Approach 2:
The patent merges the sensing circuit functionality with the existing pixel circuit structure. The sensing operation is integrated into the pixel circuit by utilizing the dual-gate transistor's inherent capability to sense its own threshold voltage or mobility. The sensing control circuit is merged with the display control circuit, allowing the same control lines and switching mechanisms to be used for both sensing and display operations. This integration reduces the overall circuit complexity by eliminating redundant components that would be required if sensing and display functions were completely separate.
3Measurement precision
If dual-gate transistors are used for sensing threshold voltage and mobility, then precise compensation is achieved, but transistor design and fabrication become more complex
Solution Approach 1:
The patent applies segmentation by dividing the transistor gate into two separate gates (first gate and second gate), which allows independent control and measurement functions. The first gate is used for normal display control while the second gate is used for sensing operations. This segmentation enables the transistor to function as both a driving element and a sensing element without requiring completely different transistor structures. The dual-gate configuration can be fabricated using standard CMOS processes with minimal modifications, as it essentially adds one more gate structure that can be formed using existing fabrication techniques.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for precise compensation of threshold voltage/mobility changes and degradation of organic light emitting diodes, ensuring consistent and uniform image luminance in organic light emitting display devices.
Implementation Method 1
organic light emitting diodes (OLEDs) that emit light through recombination of electrons and holes
Data Source
AI summary
An organic light emitting display device includes a plurality of data lines, a scan driver, a sensing control line driver, a data driver, and a switching unit. The scan driver supplies a scan signal to a plurality of scan lines. The sensing control line driver supplies a sensing control signal to a plurality of sensing control lines. The data driver supplies a data signal to a plurality of data output lines. The switching unit selectively couples each data line to one of a corresponding data output line and a corresponding sensing line. The switching unit further selectively supplies a write control signal to each write control line.