OLED Pixel Circuit Segmentation for Leakage Prevention
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Solution Overview
Problem
Organic light emitting display (OLED) devices experience display defects such as luminance unevenness and cross-talk due to current leakage from the driving transistor during simultaneous emission methods, which are not effectively addressed by existing technologies.
Innovation Solution
The OLED device incorporates a pixel structure with specific transistor configurations and capacitors to initialize and compensate the driving transistor's threshold voltage, and uses a progressive emission method to prevent current leakage by electrically separating the gate electrode of the driving transistor and the anode electrode of the organic light emitting diode, ensuring stable initialization and emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If simultaneous emission method is used, then all pixels emit light at the same time improving display speed, but current leakage occurs from driving transistor causing luminance unevenness and cross-talk
Solution Approach 1:
The emission process is segmented into multiple time slots, with pixels divided into first pixels (emitting in first time slot) and second pixels (emitting in second time slot). This temporal segmentation prevents current leakage by ensuring that not all pixels are in emission state simultaneously, thus eliminating the condition for leakage current while maintaining sequential emission capability.
Solution Approach 2:
The display operates using periodic emission cycles where different groups of pixels are activated in alternating time slots. The first emission control signal activates first pixels during first time slot, while second emission control signal activates second pixels during second time slot, creating a periodic emission pattern that prevents continuous current leakage.
2Reliability
If progressive emission method is used, then current leakage is prevented by sequential emission, but display speed is reduced compared to simultaneous emission
Solution Approach 1:
By segmenting pixels into multiple groups with different emission timings, the patent achieves progressive emission that prevents current leakage. Each group emits sequentially rather than simultaneously, which eliminates the leakage path while maintaining acceptable display refresh rates through optimized time slot allocation.
Solution Approach 2:
The emission control signals are dynamically adjusted to control different pixel groups at different times. The first emission control signal and second emission control signal operate in complementary time slots, creating a dynamic emission pattern that adapts to prevent leakage while maintaining display performance.
3Reliability
If threshold voltage compensation is implemented, then display uniformity is improved, but pixel structure complexity increases with additional transistors and capacitors
Solution Approach 1:
The second transistor serves multiple functions: it acts as a switch for the anode electrode during normal operation and simultaneously functions as part of the threshold voltage compensation circuitry. The capacitor connected to the gate of the second transistor serves dual purposes in voltage storage and compensation, reducing the need for separate dedicated compensation components.
Solution Approach 2:
The patent merges the anode electrode control function with the threshold voltage compensation function into the same transistor and capacitor structure. The second transistor and its associated capacitor are integrated to perform both switching and compensation roles, thereby reducing overall pixel complexity while achieving both goals.
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 configuration effectively prevents current leakage and reduces luminance unevenness by allowing sequential emission of pixels, improving display quality and reducing defects like luminance fluctuations.
Implementation Method 1
an organic light emitting diode, connected between the fourth node and the second power voltage providing line, to emit light based on the driving current
Data Source
AI summary
A display panel includes a plurality of pixels each including a first transistor between a first node and a second node and having a gate electrode to receive the scan signal, a second transistor between the second node and a third node in series with the first transistor and having a gate electrode to receive the initialization control signal, a driving transistor between the first power voltage providing line and the third node and having a gate electrode connected to the first node, a third transistor between the third node and a fourth node and having a gate electrode to receive the emission control signal, an organic light emitting diode, between the fourth node and the second power voltage providing line, a first capacitor between the first power voltage providing line and the first node, and a second capacitor between the second node and one of the data lines.