4T2C AMOLED Pixel Circuit Decoupling Data Writing and Threshold Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The traditional AMOLED pixel driving circuit faces complexity in data signal voltage and short compensation time, leading to uneven display brightness and lower display quality due to the need for precise threshold voltage compensation.
Innovation Solution
The proposed AMOLED pixel driving circuit employs a 4T2C structure with additional transistors and capacitors to separate the data signal voltage writing process from the reset and threshold voltage detection stages, allowing for increased reset and compensation times, and simplifies the data signal voltage by providing a reference voltage, thus effectively compensating for threshold voltage changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a 2T1C structure is used for AMOLED pixel driving, then the device complexity is reduced, but the threshold voltage compensation precision deteriorates leading to uneven display brightness
Solution Approach 1:
The patent divides the pixel driving circuit into multiple functional modules: a drive transistor, a compensation transistor, a storage capacitor, and additional compensation capacitors. This segmentation allows the threshold voltage compensation function to be separated from the basic driving function, enabling precise compensation without significantly increasing overall circuit complexity.
Solution Approach 2:
The patent implements threshold voltage compensation in advance during a dedicated compensation phase before the display phase. The compensation transistor and capacitors are configured to pre-compensate for threshold voltage variations, ensuring that the drive transistor operates with accurate compensation during the subsequent display period without requiring complex real-time adjustment mechanisms.
2Device complexity
If the data signal voltage writing process is combined with reset and threshold voltage detection stages, then the device complexity is reduced, but the compensation time is insufficient leading to poor display quality
Solution Approach 1:
The patent segments the signal processing into distinct phases: a reset phase, a threshold voltage detection phase, and a data signal writing phase. This temporal segmentation is achieved through careful configuration of the compensation transistor and capacitors, allowing each function to be performed with adequate time without requiring overly complex signal multiplexing schemes.
Solution Approach 2:
The patent employs dynamic control of the compensation transistor and capacitors through different voltage levels applied to their control terminals. By dynamically adjusting the state of these components during different phases (reset, detection, writing), the circuit can perform multiple functions sequentially with sufficient time allocation for each, improving display quality without excessive complexity.
3Device complexity
If the data signal voltage is not simplified with reference voltage, then the circuit structure is simpler, but the display brightness uniformity deteriorates
Solution Approach 1:
The patent introduces reference voltage terminals connected to capacitors that maintain stable voltage levels during operation. These reference voltages create equipotential conditions that compensate for threshold voltage variations in the drive transistor, ensuring uniform display brightness across different pixels and over time without requiring complex signal voltage modulation.
Data Source
AI summary
The present invention provides an AMOLED pixel driving circuit and a pixel driving method. The AMOLED pixel driving circuit utilizes the 4T2C structure, comprising a first, a second, a third, a fourth thin film transistors (T1, T2, T3, T4), a first, a second capacitor (C1, C2) and an organic light emitting diode (OLED) with introducing a first, a second global signals (Vselx, Vsely) and a reference voltage (Vref); by providing the reference voltage (Vref) to the first node (a) via the third thin film transistor (T3), the data signal voltage (Vdata) can be simplified to diminish the complexity of the data signal voltage (Vdata). The process of writing the data signal voltage (Vdata) into the first thin film transistor T1, i.e. the driving the thin film transistor is separated from the reset stage (Reset) and the threshold voltage detection stage (Vth sensing) with the fourth thin film transistor (T4). Thus, the reset time and the compensation time can be increased to effectively compensate the threshold voltage changes of the drive thin film transistor and the display brightness of the AMOLED becomes more even to raise the display quality.