Pixel Driving Circuit with Dual-Gate Threshold Compensation
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Solution Overview
Problem
In active matrix organic light-emitting diode (AMOLED) displays, non-uniform threshold voltages of driving transistors lead to variations in driving currents among pixels, affecting display uniformity, dark state display effect, and contrast.
Innovation Solution
A pixel driving circuit with a light emitting device, storage capacitor, and switching units is designed to write the sum of data signal voltage and threshold voltage into the driving unit, eliminating the effect of threshold voltage drift on driving current, and utilizing a small storage capacitor to improve display contrast and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional two-transistor driving circuit is used, then the circuit complexity is low, but the display uniformity deteriorates due to threshold voltage variations
Solution Approach 1:
The pixel circuit is divided into multiple functional modules: a driving unit with dual gates (first gate for data input, second gate for threshold voltage compensation), a storage capacitor for voltage holding, and multiple switching units for signal routing. This segmentation allows independent optimization of each module to achieve both simplicity and high display uniformity.
Solution Approach 2:
A storage capacitor is introduced as an intermediary element between the driving transistor and the light-emitting device. The capacitor stores the compensated gate voltage, isolating the driving transistor from threshold voltage variations and ensuring stable driving current despite manufacturing variations.
2Manufacturing precision
If the storage capacitor size is increased to improve voltage holding stability, then the display uniformity improves, but the pixel area increases reducing resolution
Solution Approach 1:
The circuit design changes the operational parameters of the driving transistor by applying dual-gate control. The second gate receives a compensation signal that adjusts the transistor's effective threshold voltage, allowing the use of a smaller storage capacitor while maintaining voltage holding stability and display uniformity.
Solution Approach 2:
The compensation for threshold voltage variations is performed in advance through the second gate of the driving transistor before the actual light emission. This preliminary compensation action eliminates the need for a large storage capacitor, as the voltage is pre-adjusted to account for transistor variations.
3Manufacturing precision
If threshold voltage compensation is implemented, then the display uniformity improves, but the device complexity increases
Solution Approach 1:
The driving transistor is designed with dual-gate functionality, where the first gate handles data input and the second gate provides threshold voltage compensation. This multi-functionality is achieved within a single transistor structure, avoiding the need for separate compensation transistors and reducing overall circuit complexity while maintaining display uniformity.
Data Source
AI summary
A pixel driving circuit and a driving method thereof, as well as a display apparatus. The driving circuit is realized by using one storage capacitor, one driving unit and five switching units, which may obtain a smaller pixel layout and facilitate improvement of display resolution. Also, a display effect of the pixels in a dark state may be improved, and the contrast be increased.