OLED Pixel Layout to Reduce Parasitic Capacitance in AID Dimming
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Solution Overview
Problem
Organic light emitting diode displays suffer from parasitic capacitance issues due to overlapping wiring lines, which degrade display quality by generating horizontal line patterns and reducing luminance, especially when using auto impulse driving (AID) dimming methods for gray scale control.
Innovation Solution
The design separates the driving source electrode of the driving transistor from the data line, preventing overlap and reducing parasitic capacitance, while using an AID dimming driving method to control emission control signals and set luminance gray scale values by adjusting the off-period length, thereby minimizing horizontal line patterns and enhancing display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If wiring lines are placed close together or made to overlap to reduce device area, then area utilization is improved, but parasitic capacitance increases which degrades display quality
Solution Approach 1:
The patent extracts the harmful overlapping region by routing the data line and driving voltage line through separate via holes (first via hole and second via hole) to connect to different electrodes. This separation removes the source of parasitic capacitance while maintaining compact layout, directly resolving the contradiction between area efficiency and parasitic capacitance reduction.
2Measurement precision
If AID dimming driving method is used to control gray scale values by adjusting off-period length, then luminance control precision is improved, but horizontal line patterns appear due to parasitic capacitance interference
Solution Approach 1:
The patent removes the parasitic capacitance source by separating the data line and driving voltage line connections through different via holes, preventing the interference that causes horizontal line patterns during AID dimming operation, thus enabling precise luminance control without display artifacts.
Solution Approach 2:
The patent introduces separate via holes as intermediary connection structures between the wiring lines and electrodes. These via holes act as isolated connection points that prevent direct capacitive coupling between the data line and driving voltage line, eliminating the horizontal line patterns while preserving the AID dimming function.
3Area of stationary object
If driving source electrode is positioned close to data line to reduce transistor area, then manufacturing area is improved, but parasitic capacitance increases causing luminance degradation
Solution Approach 1:
The patent extracts the driving voltage line from the overlapping region by routing it through a separate second via hole, removing the parasitic capacitance source that would otherwise degrade luminance. This allows the driving source electrode to be positioned close to the data line without sacrificing display quality.
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 solution effectively reduces parasitic capacitance and horizontal line patterns, ensuring consistent luminance and improved contrast ratio across the display, particularly when expressing low gray scale values, by maintaining the driving current and preventing interference between the emission control signal and data signal.
Implementation Method 1
electrons injected from one electrode and holes injected from the other electrode combine in the organic emission layer. As a result, excitons are formed. When the excitons change state, light is emitted.
Implementation Method 2
When the wiring lines are close together or overlap, parasitic capacitance occurs which degrades display quality.
Data Source
AI summary
An organic light emitting diode display includes a plurality of pixels. At least one pixel is connected to a scan line receive a scan signal, a data line to receive a data signal, and voltage line to receive a driving voltage. The at least one pixel includes a switching transistor including a switching drain electrode to output the data voltage, a driving transistor including a driving source electrode connected to the switching drain electrode, and an organic light emitting diode connected to a driving drain electrode of the driving transistor. The driving source electrode is separated from the data line.