OLED Pixel Circuit with Current Sink Line for Luminance Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing OLED display technologies face challenges in achieving uniform luminance due to variations in threshold voltage and electron mobility of drive transistors, particularly in voltage driving modes, and struggle with charging large-area circuits efficiently in electric current driving modes.
Innovation Solution
A method where a predetermined electric current is supplied to electric current sink lines to compensate for threshold voltage and electron mobility of drive transistors, converting these voltages into a unified signal to drive OLEDs, ensuring uniform luminance across the display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If voltage driving mode is used to drive OLED pixels, then the display can be driven with simple voltage signals, but uniform luminance cannot be achieved due to variations in threshold voltage and electron mobility of drive transistors
Solution Approach 1:
The patent introduces a current sink line as an intermediary component between the drive transistor and the OLED. This current sink line receives a compensation current that compensates for threshold voltage and electron mobility variations of the drive transistor, thereby enabling uniform luminance while maintaining voltage driving mode simplicity
Solution Approach 2:
The patent changes the operating parameter from direct voltage control to current-controlled voltage compensation. By supplying a compensation current through the current sink line, the system adjusts the effective voltage at the OLED to compensate for transistor variations, achieving uniform luminance output
2Manufacturing precision
If electric current driving mode is used to supply micro-electric current as data signal, then uniform image can be displayed regardless of transistor variations, but large-area circuits cannot be driven due to insufficient charging speed
Solution Approach 1:
The patent segments the charging function into two parts: a first capacitor charges during the programming period to compensate for transistor variations, and a second capacitor charges during the emission period to provide the actual drive current. This segmentation allows uniform luminance while maintaining fast charging speed for large-area circuits
Solution Approach 2:
The patent performs preliminary compensation by charging the first capacitor with a compensation current during the programming period before the actual emission. This preliminary action compensates for threshold voltage and electron mobility variations, so that the subsequent emission phase can proceed at full speed without sacrificing luminance uniformity
3Manufacturing precision
If micro-electric current is used as data signal, then uniform image display is achieved, but large amount of time is required for charging pixels due to load capacitance in data lines
Solution Approach 1:
The patent introduces a current sink line as an intermediary that supplies compensation current directly to the pixel circuit, bypassing the slow charging through load capacitance-limited data lines. This intermediary path enables fast compensation for transistor variations without being constrained by data line capacitance
Solution Approach 2:
The patent replaces the traditional voltage-based or slow current-based charging mechanism through capacitive data lines with a direct current sink line mechanism. This substitution eliminates the bottleneck caused by load capacitance, enabling fast charging while maintaining image uniformity
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 allows for stable and uniform image display regardless of transistor variations, enabling efficient charging of pixels and supporting large-area circuit designs by compensating for load capacitance.
Implementation Method 1
OLED display devices produce an image by employing light emitting diode(s), which generate light by recombining electrons and holes
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An electroluminescent display device includes pixels (140) each adapted to receive respective first and second scan signals via respective first and second lines; a scan driver (110) adapted to supply a respective scan signal to each of the scan lines and to supply a respective light emitting control signal to each of the light emitting control lines; and a data driver (120) adapted to primarily charge the pixel by sinking a predetermined electric current through a respective electric current sink line when the first scan signal is supplied to the first scan line, and to secondarily charge the respective pixel by supplying a voltage data signal to a respective one of the data lines when the second scan signal is supplied to the second scan line associated with the pixel.