Pixel Circuit Layout Using LTPS and Oxide TFTs for Low-Noise Displays
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Solution Overview
Problem
Existing display devices face challenges in achieving efficient and high-quality image display due to issues such as leakage currents, flicker noise, and voltage fluctuations caused by transistors with high electron mobility and fluctuating threshold voltages, which affect image quality and resolution.
Innovation Solution
The use of N-type low-temperature poly-silicon (LTPS) and oxide semiconductor transistors in pixel circuits, along with capacitors, to stabilize voltage and minimize leakage currents, combined with a scan driver design that includes N-type LTPS and oxide semiconductor transistors to enhance driving characteristics and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If transistors with high electron mobility are used to improve driving speed, then response time is improved, but leakage current and flicker noise increase
Solution Approach 1:
The patent applies different transistor types to different circuit positions based on local functional requirements. N-type LTPS transistors are used in positions requiring high driving speed (such as the first transistor connected between drive power nodes), while oxide semiconductor transistors are used in positions where low leakage current is critical (such as the second and third transistors connected to scan lines and reference power). This localized differentiation resolves the contradiction by optimizing each position's transistor characteristics according to its specific functional needs.
Solution Approach 2:
The patent employs a composite transistor architecture combining N-type LTPS and oxide semiconductor transistors within the same pixel circuit. This composite approach leverages the high electron mobility of LTPS transistors for driving functions while utilizing the low leakage characteristics of oxide semiconductor transistors for maintaining stability, thereby achieving both fast response and low noise performance simultaneously.
2Power
If transistors with fluctuating threshold voltages are used to improve drive capability, then current driving ability is improved, but voltage stability deteriorates
Solution Approach 1:
The patent assigns different transistor types to different functional roles within the pixel circuit. The first transistor, which requires high current driving ability for switching drive power, is implemented as an N-type LTPS transistor. In contrast, the second and third transistors, which need to maintain stable voltage connections to scan lines and reference power, are implemented as oxide semiconductor transistors with stable threshold voltages. This local differentiation resolves the contradiction by matching transistor characteristics to specific functional requirements.
Solution Approach 2:
The patent introduces oxide semiconductor transistors as intermediary elements that provide voltage stabilization throughout the circuit. These transistors act as mediators that maintain stable voltage levels at various nodes, compensating for threshold voltage fluctuations in other parts of the circuit and ensuring overall voltage stability while preserving the high drive capability provided by LTPS transistors.
3Device complexity
If conventional transistor configurations are used to simplify circuit design, then device complexity is reduced, but image quality and resolution deteriorate
Solution Approach 1:
The patent implements a differentiated transistor configuration where specific transistors are designated as N-type LTPS and others as oxide semiconductor types. This localized optimization of transistor characteristics in critical positions enables improved image quality and resolution while maintaining relatively simple overall circuit architecture, resolving the contradiction between complexity and performance.
4Speed
If light absorbing materials are used to improve transistor performance, then electron mobility is improved, but light emission efficiency deteriorates
Solution Approach 1:
The patent uses oxide semiconductor transistors in specific positions (second and third transistors) where low light absorption is critical for maintaining light emission efficiency. These transistors provide stable performance without the light-absorbing characteristics that would interfere with the light emitting element's performance, thereby resolving the contradiction between electron mobility and light emission efficiency in the relevant circuit positions.
Data Source
AI summary
A electronic device includes a processor to provide input image data, and a display device to display an image based on the input image data, the display device including pixels, wherein any one pixel among the pixels includes a first transistor connected to second node and having a gate electrode connected to a first node; a second transistor connected between a data line and the first node and having a gate electrode connected to a first line; a third transistor connected between a reference-power node and the first node and having a gate electrode connected to a second line; a fourth transistor connected between an initialization-power node and a third node and having a gate electrode connected to a third line; a fifth transistor connected between a drive-power node and the first transistor and having a gate electrode connected to a first-light-emitting-control line; a sixth transistor connected between the second node and the third node and having a gate electrode connected to a second-light-emitting-control line; and a light emitting element connected to the third node. The fourth, fifth and sixth transistors are N-type LTPS transistors.