AMOLED Pixel Structure with Shared Compensation Unit
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Solution Overview
Problem
Conventional AMOLED display technologies face issues such as brightness nonuniformity due to threshold voltage variations and IR Drop, leading to mura and afterimage phenomena, which are exacerbated by the limitations of LTPS TFTs and oxide TFTs in large-size displays.
Innovation Solution
A pixel structure comprising two adjacent pixel circuits sharing a compensation unit, which adjusts the gate voltage of driving transistors to eliminate threshold voltage influences, reducing the number of TFTs and data lines, thereby improving resolution and picture quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LTPS TFTs or oxide TFTs are used to construct pixel circuits, then mobility and stability are improved, but nonuniformity of electrical parameters (threshold voltage, mobility) occurs due to crystallization process limitations, causing brightness nonuniformity
Solution Approach 1:
The patent implements a feedback mechanism through the compensation transistor and storage capacitor that detects threshold voltage variations of the driving transistor and automatically compensates for them. The compensation transistor is configured to sense the gate-source voltage of the driving transistor, and when threshold voltage drift occurs, the storage capacitor adjusts the gate voltage of the driving transistor to maintain stable current output, thereby eliminating the need for additional compensation circuits while improving manufacturing uniformity.
Solution Approach 2:
The pixel circuit is designed to self-compensate for threshold voltage variations using its own internal components (compensation transistor and storage capacitor) without requiring external compensation circuits. The circuit automatically detects and corrects threshold voltage drift through the interaction between the compensation transistor and storage capacitor, enabling the system to serve itself and eliminate manufacturing nonuniformity issues.
2Manufacturing precision
If additional switch transistors and capacitor devices are added to compensate for nonuniformity, then brightness uniformity is improved, but device complexity and pixel area increase
Solution Approach 1:
The compensation transistor and storage capacitor are designed to serve multiple functions: the compensation transistor acts as both a switching element and a sensing element for threshold voltage detection, while the storage capacitor simultaneously stores compensation voltage and regulates the driving transistor gate voltage. This multi-functionality eliminates the need for separate compensation circuits, reducing device complexity while maintaining brightness uniformity.
Solution Approach 2:
The patent merges the compensation function with the existing pixel circuit components by integrating the compensation transistor and storage capacitor into the standard 2T1C or 3T1C pixel structure. The compensation transistor is combined with the switching transistor, and the storage capacitor is integrated with the existing capacitor, creating a unified circuit that performs both driving and compensation functions without increasing overall device complexity.
3Area of stationary object
If power supply lines are extended to cover large display areas, then coverage is improved, but IR Drop increases causing voltage variations and brightness nonuniformity
Solution Approach 1:
The patent implements local quality by making each pixel circuit independently self-regulating through its own compensation transistor and storage capacitor. Each pixel detects and compensates for its local voltage variations caused by IR Drop, rather than relying on a centralized power supply system. This localized compensation ensures that each pixel maintains stable operating voltage regardless of its position in the display, eliminating brightness nonuniformity across large areas.
Solution Approach 2:
The patent segments the power supply system into independent pixel-level units, where each pixel circuit operates autonomously with its own compensation mechanism. By dividing the large display into independent functional units, each with its own voltage regulation capability, the system eliminates the cumulative IR Drop effects that occur in centralized power distribution, ensuring uniform voltage across the entire large display area.
4Measurement precision
If data lines are increased to control each pixel independently, then resolution is improved, but driving chip cost and complexity increase
Solution Approach 1:
The patent uses the compensation transistor to create an electrical copy or replica of the driving transistor's threshold voltage characteristics. By sensing the gate-source voltage of the driving transistor through the compensation transistor, the system creates an electrical copy of the threshold voltage variation, which is then stored and used for compensation. This copying mechanism enables precise threshold voltage compensation without requiring additional data lines, maintaining high resolution while reducing driving chip complexity.
Data Source
AI summary
Provided are a pixel structure and driving method thereof, and a display apparatus. The pixel structure comprises a plurality of pixel units and compensation units corresponding to the pixel units. Each of the pixel units comprises two adjacent pixel circuits which are a first pixel circuit and a second pixel circuit. The first pixel circuit comprises a first driving transistor (DTFT1) and a first display device (OLED1), and the second pixel circuit comprises a second driving transistor (DTFT2) and a second display device (OLED2), wherein the first pixel circuit and the second pixel circuit share the compensation unit and are controlled by a same data line (Data). The compensation unit is configured to adjust a gate voltage of the first driving transistor (DTFT1) in the first pixel circuit to eliminate the influence of the threshold voltage of the first driving transistor (DTFT1) on the driving current of the first display device (OLED1), and to adjust a gate voltage of the second driving transistor (DTFT2) in the second pixel circuit to eliminate the influence of the threshold voltage of the second driving transistor (DTFT2) on the driving current of the second display device (OLED2). The pixel structure can reduce the pixel size and obtain higher resolution.