Pixel Circuit Fourth Transistor Reduces Image Sticking
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Solution Overview
Problem
Display devices experience degradation deviation and image sticking due to differences in threshold voltage compensation across pixels, particularly when applying black and white data voltages, leading to uneven degradation and image quality issues.
Innovation Solution
Incorporating a fourth transistor that maintains a turn-on state and is coupled in series with the third transistor, with its gate electrode connected to a DC power source, to equalize the source voltage and reduce gate-source voltage fluctuations, thereby minimizing degradation deviation and image sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel structure with threshold voltage compensation is used, then the pixel can operate with basic current control, but degradation deviation and image sticking occur due to gate-source voltage fluctuations
Solution Approach 1:
A fourth transistor is introduced as an intermediary element coupled in series with the third transistor. This fourth transistor maintains a sustained turn-on state to serve as a stable intermediary connection between the first node and third node, equalizing source voltage and reducing gate-source voltage fluctuations across pixels, thereby minimizing degradation deviation and image sticking while maintaining reliable current control
2Device complexity
If the third transistor is used alone for current control, then the circuit remains simple, but source voltage unequalization occurs leading to image sticking
Solution Approach 1:
The fourth transistor is added as a series element with the third transistor, creating a two-transistor series connection between the first node and third node. This additional intermediary component equalizes source voltage across pixels and stabilizes gate-source voltage, preventing image sticking while maintaining reasonable circuit complexity
3Illumination intensity
If black and white data voltages are applied with conventional structures, then the display can show high contrast images, but degradation deviation occurs between different voltage states
Solution Approach 1:
The fourth transistor maintains a sustained turn-on state and acts as a stable intermediary that equalizes source voltage regardless of whether black or white data voltages are applied. This reduces gate-source voltage fluctuations under different voltage states, ensuring uniform degradation characteristics while preserving high contrast image display capability
Data Source
AI summary
A pixel includes a light emitting device, a first transistor for controlling an amount of current flowing from a first power source to a second power source via the light emitting device, in response to a voltage applied to a first node, a second transistor coupled between a data line and a second node corresponding to a first electrode of the first transistor, and including a gate electrode coupled to a first scan line, a third transistor coupled between the first node and a third node corresponding to a second electrode of the first transistor, and including a gate electrode coupled to the first scan line, and a fourth transistor coupled between the third transistor and the third node, and configured to maintain a turn-on state.