Pixel Driving Circuit Layout for Low-Brightness Color Uniformity

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Solution Overview

Problem

Existing display panels using low temperature polysilicon technologies suffer from significant leakage currents and uneven electrical properties, leading to color unevenness at low brightness due to manufacturing limitations.

Innovation Solution

A display panel design featuring pixel driving circuits with transistors connected in parallel, where the first transistor has a higher threshold voltage and carrier mobility than the second transistor, with the second transistor turning on earlier to control the light-emitting device, thereby slowing down the increasing driving current and improving color uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If low temperature polysilicon technology is used for pixel driving circuits, then manufacturing process is simplified, but leakage current increases and transistor electrical properties become uneven

Engineering Contradiction:

Improvemanufacturing processVSAvoidtransistor electrical properties uniformity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The pixel driving circuit is divided into multiple transistor units with different characteristics. Specifically, the circuit includes first transistor units with silicon semiconductor active layers and second transistor units with oxide semiconductor active layers, each contributing differently to the overall circuit performance to achieve uniform electrical properties while maintaining manufacturability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the pixel driving circuit use transistors with locally optimized properties. The first transistor units and second transistor units are configured with different threshold voltages and carrier mobilities to compensate for manufacturing variations and achieve uniform electrical characteristics across the entire display panel

Inventive Principle:

Principle #3Local quality

2Reliability

If transistors with uniform electrical properties are implemented, then color unevenness is reduced, but device complexity increases

Engineering Contradiction:

Improvecolor uniformityVSAvoidtransistor structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Multiple transistor units with different characteristics are merged into a single functional block within the pixel driving circuit. The first transistor units and second transistor units work together in parallel to achieve uniform electrical properties, effectively combining their complementary strengths to reduce color unevenness without requiring separate circuits

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS20230309342A1Display panel, pixel driving circuits, and display device

Publication Date: 2023.09.28 WUHAN CHINA STAR OPTOELECTRONICS TECH CO LTD

AI summary

A display panel, a pixel driving circuit, and a display device are provided. Driving transistors include a first transistor and a second transistor connected in parallel. An absolute value of a threshold voltage of the first transistor is greater than an absolute value of a threshold voltage of the second transistor. A carrier mobility of the first transistor is greater than a carrier mobility of the second transistor. A driving current is affected by characteristics of the second transistor and an increase speed is slowed down, which improves a problem of color unevenness of the display panel at low brightness.