OLED Pixel Driving Circuit Threshold Voltage Sensing
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Solution Overview
Problem
Traditional OLED pixel driving circuits face issues with non-uniform display due to inconsistent threshold voltages of driving thin film transistors, which are exacerbated by aging, leading to decreased image quality and increased manufacturing costs when compensation is attempted through additional reference voltage wiring.
Innovation Solution
An OLED pixel driving circuit with a third thin film transistor and a switch, incorporating a digital to analog converter and an analog to digital converter, operates in both display and sensing modes to sense and compensate for threshold voltages without the need for additional reference voltage signals, thereby eliminating the influence of threshold voltages on current flow and improving display uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a traditional 2T1C pixel driving circuit is used, then the device complexity is low and manufacturing is simple, but the display uniformity deteriorates due to threshold voltage inconsistency and aging
Solution Approach 1:
The patent applies preliminary action by sensing the threshold voltage of the driving thin film transistor before the OLED display operation. The sensing transistor and switch are configured to perform threshold voltage sensing in advance, allowing the system to compensate for threshold voltage variations before they affect display uniformity. This proactive approach eliminates the need for complex real-time compensation circuits while maintaining display quality.
2Manufacturing precision
If additional reference voltage wiring is added for compensation, then the display uniformity improves, but the aperture ratio of pixels decreases and manufacturing costs increase
Solution Approach 1:
The patent merges the sensing transistor and switch with the existing pixel driving circuit components. The sensing transistor shares the same pixel structure and utilizes existing wiring and electrodes, eliminating the need for additional reference voltage wiring. This integration maintains display uniformity through threshold voltage sensing while preserving the aperture ratio by avoiding extra external wiring connections.
3Manufacturing precision
If more transistors and components are added for threshold voltage compensation, then the display uniformity improves, but the manufacturing precision deteriorates due to process variability
Solution Approach 1:
The patent applies local quality by configuring the sensing transistor with specific structural characteristics that optimize its sensing capability. The sensing transistor is designed with appropriate channel width, length, and material composition tailored for threshold voltage sensing, while the driving transistor maintains its original structure for current driving. This specialized local design enables accurate threshold voltage compensation without requiring multiple different transistor types, simplifying the manufacturing process.
Data Source
AI summary
The OLED pixel driving circuit adds the third thin film transistor (T3) and arranges the switch (K) on the basis of the 2T1C structure. The first pin (K1) of the switch (K) is electrically coupled to the drain of the third thin film transistor (T3), and the second pin (K2) is electrically coupled to the digital to analog converter (DAC), and the third pin is electrically coupled to the analog to digital converter (ADC). The switch signal (Switch) is used to control the switch (K) to connect the first pin (K1) and the second pin (K2) for entering the display mode, and the switch signal (Switch) is used to control the switch (K) to connect the first pin (K1) and the third pin (K3) for entering the sensing mode so that the analog to digital converter (ADC) can sense the threshold voltage (Vth) of the second thin film transistor (T2).