OLED Display Pixel Circuit Merging for Aperture Ratio
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Solution Overview
Problem
Conventional light emitting displays require a large number of pixel circuits and emission control lines, leading to reduced aperture ratio and increased size due to the need for multiple pixel circuits to drive individual OLEDs, and suffer from color breakup due to sequential emission of colors.
Innovation Solution
A light emitting display design where multiple OLEDs share a single pixel circuit, with a driving circuit and switching circuits that compensate for transistor threshold voltages, allowing uniform current distribution and controlled emission timing to minimize color breakup, reducing the number of pixel circuits, data lines, and power lines, and enhancing aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If one pixel circuit is assigned to each OLED, then each OLED can be independently controlled, but the number of pixel circuits increases leading to larger display size and reduced aperture ratio
Solution Approach 1:
The patent merges multiple OLEDs (specifically 2x2=4 OLEDs) into a single pixel circuit unit. The pixel circuit includes transistors (T1-T6) and capacitors (Cst1, Cst2) that collectively control four OLEDs (OLED11-OLED44) arranged in a 2x2 matrix. This merging reduces the number of pixel circuits from 4 to 1 per display unit, decreasing overall display area while maintaining independent control capability through selective transistor switching.
Solution Approach 2:
The pixel circuit is designed with multi-functional transistors that can control multiple OLEDs. For example, transistor T1 controls OLED11 and OLED21, transistor T2 controls OLED12 and OLED22, transistor T3 controls OLED33 and OLED43, and transistor T4 controls OLED34 and OLED44. This universal control mechanism allows a single pixel circuit to perform the function of multiple separate pixel circuits, reducing the total number of components and display area.
2Extent of automation
If multiple emission control lines are used to control different OLED rows, then emission timing can be controlled, but the aperture ratio deteriorates due to the emission control lines occupying space
Solution Approach 1:
The patent merges the emission control function into the existing scan line structure. Instead of adding separate emission control lines for each OLED row, the scan lines (S1, S2) are used to control the timing of multiple OLEDs simultaneously. The pixel circuit uses scan signals applied to scan lines to control the switching transistors, thereby controlling emission timing without requiring additional dedicated emission control lines that would reduce aperture ratio.
Solution Approach 2:
The scan lines are given multi-functional capability to serve both as data transmission lines and as emission control lines. The scan signals applied to the scan lines control the timing of emission for multiple OLEDs (e.g., OLED11-OLED21 for S1, OLED33-OLED44 for S2) through the pixel circuit's transistor switching mechanism. This eliminates the need for separate emission control lines, preserving aperture ratio while maintaining precise emission timing control.
3Ease of operation
If a large number of pixel circuits are used to drive individual OLEDs, then each OLED can be independently driven, but the size of the data driving part increases
Solution Approach 1:
The patent merges multiple OLED driving functions into a single pixel circuit. Instead of having separate pixel circuits for each OLED, the pixel circuit integrates control for four OLEDs (OLED11-OLED44) using shared transistors (T1-T6) and capacitors (Cst1, Cst2). This merging reduces the number of pixel circuits from 4 to 1, thereby reducing the size of the data driving part while maintaining independent driving capability through selective transistor activation.
Solution Approach 2:
The transistors within the pixel circuit are designed with universal control capability. For instance, transistor T1 controls both OLED11 and OLED21, transistor T2 controls OLED12 and OLED22, and so on. This multi-functional transistor design allows a single pixel circuit to independently drive multiple OLEDs, reducing the overall number of pixel circuits and the associated data driving part size.
4Object-affected harmful factors
If sequential emission of colors is used, then color breakup can occur, but controlling emission timing requires additional emission control lines
Solution Approach 1:
The patent merges the emission control function with the scan line function, eliminating the need for separate emission control lines. The scan lines (S1, S2) control the emission timing of multiple OLEDs simultaneously through the pixel circuit's transistor switching mechanism. This merging approach prevents color breakup by enabling precise timing control while avoiding the device complexity of additional emission control lines.
Solution Approach 2:
The scan lines are designed with universal functionality to control both data transmission and emission timing. The scan signals applied to scan lines control the sequential emission of colors for multiple OLEDs (e.g., controlling OLED11-OLED21 for S1, OLED33-OLED44 for S2) through the pixel circuit. This multi-functional design prevents color breakup while avoiding the need for additional emission control lines, thereby reducing device complexity.
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
The design achieves uniform brightness, reduces the size of the data driving part, improves aperture ratio, and prevents color breakup by allowing multiple OLEDs to emit light through a single pixel circuit, thereby minimizing the number of required pixel circuits and wiring lines.
Implementation Method 1
Electrons and holes are injected into the emission layer so that they can be re-combined to generate exciters that emit light when their energies are reduced
Data Source
AI summary
A light display includes scan lines arranged in a row direction to transmit scan signals, a data line arranged in a column direction to transmit a data signal, an image display unit including emission control lines arranged in the row direction to transmit emission control signals, and a pixel in a region defined by the scan lines and the data line. The pixel has a driving circuit for receiving the signals, the data signal, the emission control signals, and a power to drive a current, a switching circuit connected with the driving circuit to receive the current, the switching circuit for selectively applying the current in accordance with the emission control signals, and organic light emitting diodes (OLEDs) positioned on different rows of the image display unit and connected with the switching circuit to receive the current in accordance with an operation of the switching circuit and to emit light.