Pixel Circuit Sharing Signal Lines for AMOLED Brightness Uniformity
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Solution Overview
Problem
In existing AMOLED display panels, threshold voltage drift of driving TFTs leads to non-uniform display brightness, and integrating touch screen and driving circuits in in-cell TSPs complicates fabrication due to limited pixel unit space.
Innovation Solution
Integration of a pixel compensation module and a touch detection module within the pixel circuit, sharing data voltage and scan signal lines, reduces signal lines and pixel pitch, and decouples operating current from driving transistor threshold voltage, thus avoiding brightness non-uniformity and enhancing integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If touch screen and driving circuits are integrated in in-cell TSP pixel units, then display thickness is reduced and light transmittance is improved, but fabrication complexity increases due to limited pixel unit space
Solution Approach 1:
The patent merges the touch detection module and pixel driving circuit into a single integrated pixel circuit structure. The touch detection module shares signal lines (data voltage line and scan signal lines) with the pixel driving circuit, combining two previously separate functions into one unified circuit that can be fabricated together in the same pixel unit without requiring additional space.
Solution Approach 2:
The pixel circuit is designed to perform multiple functions simultaneously: it serves as both the pixel driving circuit for OLED control and the touch detection module for touch input. By making the circuit multi-functional, the patent eliminates the need for separate dedicated spaces for touch and display functions, thereby reducing overall device complexity while maintaining both functionalities.
2Adaptability or versatility
If multiple driving circuit TFTs are added to pixel units for in-cell TSP, then touch detection capability is achieved, but available space in pixel unit is reduced
Solution Approach 1:
The patent combines the touch detection module with the existing pixel driving circuit by sharing common signal lines (data voltage line and scan signal lines). This merging approach allows touch detection functionality to be added without requiring separate dedicated signal lines or additional TFTs, thereby maintaining the original pixel unit space while achieving touch capability.
Solution Approach 2:
The pixel driving circuit is transformed into a multi-functional structure that simultaneously performs pixel driving and touch detection. By making the circuit universal, the patent enables one circuit to fulfill multiple roles, eliminating the need for additional components that would consume pixel unit space.
3Illumination intensity
If conventional pixel driving circuit is used, then OLED is driven to emit light, but threshold voltage drift of driving TFTs causes non-uniform display brightness
Solution Approach 1:
The patent implements a compensation mechanism where the operating current is decoupled from the driving transistor's threshold voltage through a feedback-like circuit configuration. The pixel compensation module continuously adjusts the current based on the actual threshold voltage of the driving TFT, compensating for drift over time and ensuring uniform brightness across all pixels even as transistor characteristics change.
Solution Approach 2:
The patent changes the circuit configuration to decouple the operating current parameter from the driving transistor's threshold voltage parameter. By modifying the circuit topology to include compensation elements that reference other stable voltage or current parameters, the system becomes insensitive to threshold voltage variations, thereby maintaining brightness uniformity despite parameter drift.
Data Source
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AI summary
A pixel circuit, a display panel and a display apparatus. The pixel circuit comprises a pixel compensation module, a light emitting module and a touch detection module; the pixel compensation module comprises first to fifth switch units, a pixel driving unit and an energy storage unit; and the touch detection module comprises a detection sub-module and an output sub-module. In the pixel circuit, a pixel compensation module and a touch detection module are integrated, and the pixel compensation module and the touch detection module share a data voltage line and scan signal lines. As such, it is possible to reduce the number of signal lines, such that the pitch of pixels is dramatically reduced and IC cost is decreased, achieving higher pixel density. At the same time, in the pixel circuit, the operating current flowing through the electroluminescent unit is not influenced by the threshold voltage of the corresponding driving transistor, and it is possible to avoid nonuniformity in brightness of display caused by threshold voltage drift of driving transistors.