OLED Pixel Circuit Sensing for Luminance Uniformity
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Solution Overview
Problem
Conventional organic light emitting displays face challenges in maintaining uniform luminance due to the deterioration of organic light emitting diodes and non-uniformity in threshold voltage and mobility of drive transistors, leading to reduced luminance and inconsistent image display over time.
Innovation Solution
An organic light emitting display system that includes a sensing unit to monitor the deterioration of organic light emitting diodes and drive transistors, a switching unit to connect the sensing unit with power and data lines, and a control block to store and process the sensed information, generating adjusted data signals to compensate for these changes, ensuring uniform luminance across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional organic light emitting display is used without sensing unit, then device complexity is low, but luminance uniformity deteriorates due to OLED deterioration and transistor parameter variations
Solution Approach 1:
The sensing unit performs preliminary characterization of OLED parameters (threshold voltage, mobility, leakage current) and transistor parameters before display operation. This preliminary action allows the system to pre-compensate for component variations and deterioration, maintaining luminance uniformity without requiring complex real-time adjustments during display operation.
Solution Approach 2:
The sensing unit continuously monitors OLED and transistor parameters, providing feedback to the control circuit. The control circuit adjusts drive signals based on this feedback to compensate for component variations and deterioration, ensuring stable luminance output. This closed-loop feedback mechanism resolves the contradiction by using measured information to maintain performance.
2Reliability
If sensing unit is added to monitor OLED and transistor parameters, then luminance uniformity is maintained, but device complexity increases
Solution Approach 1:
The sensing unit is integrated into the pixel circuit itself, allowing each pixel to self-characterize its own OLED and transistor parameters. This self-service approach eliminates the need for external complex sensing equipment and reduces overall device complexity while maintaining reliable luminance consistency through self-compensation.
Solution Approach 2:
The sensing functions are merged with the existing pixel circuit structure, sharing common elements such as transistors, capacitors, and signal lines. This integration reduces the additional complexity that would result from completely separate sensing circuits while achieving reliable parameter monitoring and compensation.
3Stability of the object's composition
If characterisation of pixel parameter values is performed, then compensation for deterioration is achieved, but manufacturing precision requirements increase
Solution Approach 1:
Instead of requiring tight manufacturing control of physical parameters, the system measures actual parameter values (threshold voltage, mobility, leakage current) and compensates through electrical parameter adjustments. This approach shifts from controlling manufacturing precision to adapting to parameter variations through measurement and compensation, reducing manufacturing precision requirements.
Solution Approach 2:
The system discards the assumption of uniform component parameters and instead recovers individual parameter values through sensing and characterization. By measuring and compensating for each pixel's specific parameters, the system achieves stability without requiring high manufacturing precision to produce uniform components.
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
The system effectively maintains uniform luminance by compensating for the deterioration of organic light emitting diodes and variations in drive transistor threshold voltage and mobility, thereby ensuring consistent image display regardless of these changes.
Implementation Method 1
the organic light emitting diode generating light by means of the recombination of electrons and holes
Data Source
AI summary
An organic light emitting display capable of displaying an image with uniform luminance regardless of deterioration of an organic light emitting diode and threshold voltage/mobility of a drive transistor is disclosed. The organic light emitting display senses deterioration of the organic light emitting diode and the threshold voltage and/or mobility of a drive transistor and modifies the data supplied to the pixel according to the sensed parameters.