OLED Sense TFT Grouping Reduces RC Loading
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Solution Overview
Problem
As AMOLED display devices increase in size and resolution, the resistance-capacitance (RC) loading of sense lines increases, leading to insufficient charging and a suboptimal compensation effect for threshold voltage drift in driving TFTs, especially oxide TFTs, making it difficult to achieve desired display performance.
Innovation Solution
The OLED driving circuit incorporates a plurality of sense TFTs divided into groups, with each group sharing a common gate and source electrode connected to a single sense line, reducing parasitic capacitance and RC loading, thereby increasing the charging rate of the sense line and improving compensation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the display device size and resolution are increased, then the display quality is improved, but the RC loading of sense line increases remarkably
Solution Approach 1:
The patent divides the array substrate into multiple banks, with each bank containing a subset of OLEDs and their corresponding sense TFTs. This segmentation allows the sense line to serve a limited number of TFTs within each bank, reducing the total capacitance load on the sense line while maintaining high-resolution display capability across the entire panel.
2Device complexity
If the sense line is charged at a small charging rate, then the RC loading is reduced, but the compensation effect becomes insufficient
Solution Approach 1:
The patent introduces a bank switching mechanism that dynamically changes which sense TFTs are activated based on the current bank being scanned. During each frame period, only sense TFTs in the active bank are charged through the sense line, effectively reducing the simultaneous capacitance load while ensuring adequate charging time and voltage for threshold voltage compensation.
3Speed
If multiple sense TFTs share a same source electrode connected to a same sense line, then the charging rate of sense line is improved, but the parasitic capacitance increases
Solution Approach 1:
By segmenting the array substrate into multiple banks and limiting each sense line to serve only the sense TFTs within its corresponding bank, the patent reduces the number of TFTs that simultaneously draw charge from the sense line. This segmentation approach lowers the effective parasitic capacitance compared to a fully shared configuration, while still achieving improved charging rates through reduced load.
Data Source
AI summary
An OLED driving circuit, an array substrate and a display device are provided. The OLED driving circuit includes a plurality of driving TFTs and a plurality of sense TFTs. Each sense TFT is configured to compensate for a threshold voltage of the respective driving TFT. Each sense TFT corresponds to a respective one of the driving TFTs, a source electrode of each sense TFT is connected to a sense line, and a drain electrode thereof is connected to a drain electrode of the respective driving TFT. The plurality of sense TFTs is divided into a plurality of groups, each group includes at least two sense TFTs which share a same gate electrode and a same source electrode and are connected to a same sense line.