OLED Pixel Circuit and Readout for High-Resolution Brightness Control
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Solution Overview
Problem
As display devices are downscaled and resolution increases, the limited range of current flowing through each pixel makes it difficult to control pixel brightness effectively.
Innovation Solution
A display device with a pixel configuration that includes multiple transistors and emission control lines, along with a read-out circuit, allowing for precise control of brightness through time-multiplexing and pulse width modulation, and a read-out circuit for measuring electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pixel size is reduced to increase resolution, then display resolution is improved, but the range of current flowing through each pixel is limited making brightness control difficult
Solution Approach 1:
The pixel circuit is divided into multiple functional blocks: a first transistor for main current control, a second transistor for emission control, a third transistor for readout, and a fourth transistor for initialization. This segmentation allows each transistor to specialize in specific brightness control tasks, enabling precise brightness adjustment despite limited current range in small pixels.
Solution Approach 2:
The patent implements dynamic brightness control through time-multiplexed operation of multiple transistors. The first transistor controls current during display periods, while the second transistor provides emission control during specific time windows. This dynamic, time-based control strategy enables precise brightness modulation by controlling the temporal sequence of transistor activation rather than relying solely on static current range.
2Ease of operation
If multiple transistors and emission control lines are added to expand current control range, then brightness control is improved, but device complexity increases
Solution Approach 1:
Each transistor in the pixel circuit is designed with multi-functionality: the first transistor serves as both the main current control element and the emission control transistor when needed, while the second transistor provides both emission control and readout functionality. This universal design reduces the total number of dedicated components while maintaining precise brightness control capability.
Solution Approach 2:
The patent merges the functions of multiple transistors into integrated control units. The first and second transistors work together as a combined control system where the first transistor handles primary current regulation and the second transistor provides emission modulation. This merging approach achieves enhanced brightness control without proportionally increasing circuit complexity.
3Measurement precision
If read-out circuit is added to measure electrical properties, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The read-out circuit is designed to measure electrical properties of the pixel transistors using the pixel's own operating characteristics. The circuit utilizes the existing transistor structures and control signals to perform self-diagnostic measurements of threshold voltage, mobility, and other electrical properties without requiring external test equipment or additional complex measurement apparatus.
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
Enables efficient brightness adjustment and high-resolution display with reduced pixel size by expanding the range of data voltage and facilitating control of pixel luminance through pulse amplitude modulation and pulse width modulation.
Implementation Method 1
each of a plurality of pixels of a pixel array includes an OLED
Implementation Method 2
a first organic light-emitting diode connected between the second electrode of the seventh transistor and a ground node
Data Source
AI summary
A display device includes pixels arranged in rows and columns, a scan driver, and a read-out circuit, wherein the read-out circuit is configured to read-out electrical properties of a pixel through the read-out line. The first pixel includes a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor, a ninth transistor, a first organic light-emitting diode connected between a second electrode of the seventh transistor and a ground node to which a ground voltage is applied, a second organic light-emitting diode between the second electrode of the eighth transistor and the ground node, and a third organic light-emitting diode connected between the second electrode of the ninth transistor and the ground node.