OLED Degradation Sensing via Parasitic Capacitor Current Integration
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Solution Overview
Problem
Existing organic light emitting display technologies face challenges in accurately and efficiently sensing the degradation of organic light emitting diodes (OLEDs) due to large parasitic capacitance in sensing lines, leading to increased sensing time and variability, which results in luminance deviations and image sticking phenomena.
Innovation Solution
The implementation of a current sensing method using sensing units connected to each pixel through sensing lines, which sense the amount of carriers accumulated in the parasitic capacitor of the OLED during driving current flow, employing current integrators or comparators to reduce sensing time and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage sensing method is used to sense OLED degradation by storing anode voltage in parasitic capacitor of sensing line, then degradation sensing is achieved, but sensing time increases significantly due to large parasitic capacitance
Solution Approach 1:
The patent extracts the sensing function from the voltage storage approach and implements it through current integration. Instead of storing voltage in the parasitic capacitor and then sensing it (which requires long charging time), the invention directly integrates current through the parasitic capacitor during the sensing period, eliminating the need for separate voltage storage and sensing steps. This extraction of the sensing function from voltage storage enables significantly faster sensing operation.
Solution Approach 2:
The patent replaces the voltage-based sensing mechanism with a current-based integration mechanism. Instead of using the parasitic capacitor to store voltage and then sense that voltage (a two-step process), the invention uses the same parasitic capacitor to integrate current directly during the sensing period. This substitution of voltage storage with current integration fundamentally changes the sensing mechanism, reducing the time required to achieve measurable results.
2Quantity of substance
If parasitic capacitance of sensing line is large (several hundreds to several thousands of picofarads), then voltage can be stored for sensing, but time required to charge the parasitic capacitor at sensed voltage level increases significantly
Solution Approach 1:
The patent introduces dynamic sensing operation where the sensing process occurs during the active charging period rather than requiring separate static storage and sensing phases. By performing current integration dynamically during the sensing time window, the system utilizes the charging process itself for sensing purposes, eliminating the need to wait for complete voltage stabilization. This dynamic approach allows the large parasitic capacitor to be charged and sensed simultaneously, reducing total sensing time.
Solution Approach 2:
The patent makes the charging process continuous and useful by performing current integration throughout the charging period. Instead of charging the parasitic capacitor and then stopping to sense the voltage (discontinuous operation), the invention continuously integrates current during the entire charging process. This continuous useful action ensures that the charging time is not wasted but is instead utilized for sensing, effectively eliminating idle time and reducing total operation time.
3Ease of operation
If sensing lines have different parasitic capacitances due to data lines adjacent to sensing lines, then sensing can be performed, but obtaining accurate sensing value becomes difficult
Solution Approach 1:
The patent applies local quality by making each pixel's sensing operation independent and localized to its specific parasitic capacitor. Instead of trying to compensate for variations in parasitic capacitance across different sensing lines, the invention performs separate current integration for each pixel, where each pixel's sensing operation is localized to its own unique parasitic capacitor. This localization allows each pixel to be sensed independently with its own specific parasitic capacitance characteristics, eliminating the need for cross-line compensation and ensuring accurate sensing values for each pixel regardless of adjacent data lines.
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 approach significantly reduces sensing time and enhances accuracy by utilizing the OLED's parasitic capacitor for current sensing, allowing for timely compensation for degradation deviations and maintaining image quality.
Implementation Method 1
sense an amount of carriers accumulated in a parasitic capacitor of the OLED of the corresponding one of the pixels
Implementation Method 2
when a driving current flows in the OLED
Data Source
AI summary
An organic light emitting display includes a display panel including a plurality of pixels, each of the plurality of pixels including an organic light emitting diode (OLED) and a driving thin film transistor (TFT) to control an emission amount of the OLED, the plurality of pixels connected to respective sensing lines; and at least one sensing unit connected to a corresponding one of the pixels through the respective sensing line, the at least one sensing unit configured to sense an amount of carriers accumulated in a parasitic capacitor of the OLED of the corresponding one of the pixels when a driving current flows in the OLED, the at least one sensing unit thereby sensing a degradation of the OLED.