OLED Degradation Sensing via TFT Gate-Source Voltage Control
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Solution Overview
Problem
Existing organic light emitting displays face challenges in accurately sensing degradation of organic elements due to increased manufacturing costs and reduced lifespan caused by the need for multiple current sources and complex circuit designs, particularly in independent sensing line structures, and inaccurate degradation sensing in shared sensing line structures.
Innovation Solution
A method that applies a sensing data voltage and initialization voltage to the gate and source nodes of a driving TFT to control the organic element, using the drain-to-source current to charge a line capacitor and output a sensing voltage indicative of the degradation degree, allowing for accurate sensing without separate current sources and enabling individual subpixel control even in shared sensing line structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an independent sensing line structure is used to accurately sense degradation of each organic element, then sensing accuracy is improved, but aperture ratio decreases and current density increases leading to increased degradation speed and reduced lifespan
Solution Approach 1:
The patent applies preliminary action by performing degradation sensing during the initialization period before the organic element is fully operated. The sensing is conducted in an initialization period, allowing the system to detect degradation early when the organic element has not yet accumulated significant operational stress, thus avoiding accelerated degradation during normal operation.
Solution Approach 2:
The patent implements periodic action by conducting degradation sensing at specific intervals during the initialization period rather than continuously. The sensing operation is performed periodically during the initialization phase, allowing the organic element to be operated at normal current densities during other periods while still achieving accurate degradation monitoring.
2Measurement precision
If multiple current sources are connected to each subpixel through sensing lines to uniformly set sensing currents, then sensing accuracy is improved, but manufacturing cost and circuit design area increase
Solution Approach 1:
The patent applies universality by making the data line serve multiple functions: it acts as both the data signal transmission line during normal operation and the sensing line for degradation detection during the initialization period. This eliminates the need for separate current sources and dedicated sensing lines, reducing circuit complexity while maintaining sensing capability.
Solution Approach 2:
The patent implements self-service by using the existing data line and gate driving circuitry to perform the sensing function without requiring external current sources. The gate driving circuit automatically provides the necessary sensing current through the data line during the initialization period, allowing the system to self-perform degradation sensing using its own internal resources.
3Measurement precision
If sensing lines are assigned to each subpixel in an independent sensing line structure, then individual organic elements can be operated and degradation degree directly sensed, but aperture ratio decreases
Solution Approach 1:
The patent applies universality by making the data line serve multiple functions: it acts as both the data signal transmission line during normal operation and the sensing line for degradation detection during the initialization period. This eliminates the need for separate current sources and dedicated sensing lines, reducing circuit complexity while maintaining sensing capability.
Data Source
AI summary
A method for sensing degradation of an organic light emitting display includes an initialization step for applying a sensing data voltage to a gate node of a driving TFT and applying an initialization voltage to a source node of the driving TFT, a boosting step for floating the gate node and the source node of the driving TFT and applying a drain-to-source current of the driving TFT to an organic element, a sensing step for again applying the initialization voltage to the source node of the driving TFT, setting a gate-to-source voltage of the driving TFT depending on a degradation degree of the organic element, and storing the drain-to-source current of the driving TFT determined by the set gate-to-source voltage in a line capacitor, and a sampling step for outputting a voltage stored in the line capacitor as a sensing voltage.