Pixel Driving Circuit Coupling Capacitance Luminance Stability
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Solution Overview
Problem
Conventional methods for compensating the driving switch in OLED displays face limitations due to unstable current driven by TFTs, leading to inhomogeneous luminance, and insufficient research on capacitance configurations affects the compensation effect.
Innovation Solution
A pixel driving circuit with a driving and compensation sub-circuit, data writing sub-circuit, and coupling capacitance is implemented, where the ratio of the coupling capacitance value to the sum of both capacitance values is greater than a preset value based on maximum luminance fluctuation, adjusting the capacitance configuration to improve luminance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional three-terminal device compensation is used for the driving switch, then the threshold voltage shift can be compensated, but the luminance homogeneity and stability remain insufficient due to manufacturing fluctuations
Solution Approach 1:
The pixel driving circuit is divided into functional sub-circuits: a first sub-circuit for threshold voltage compensation using a three-terminal device, and a second sub-circuit for luminance stability control using a five-terminal device. This segmentation allows each sub-circuit to specialize in a specific compensation function, improving overall luminance stability without excessive complexity in any single component.
Solution Approach 2:
The patent transitions from conventional three-terminal device compensation to incorporating a five-terminal device, adding two additional control terminals. This dimensional expansion enables independent control of compensation parameters, allowing precise adjustment of capacitance values to achieve optimal luminance homogeneity while maintaining manageable device complexity through systematic control.
2Illumination intensity
If the capacitance value ratio is not optimized, then the circuit design is simple, but the luminance fluctuation exceeds acceptable limits
Solution Approach 1:
The patent establishes a specific mathematical relationship for the capacitance value ratio: the ratio of the first capacitance value to the sum of the first and second capacitance values must be within 0.4 to 0.6. This parameter optimization ensures that the compensation effect achieves optimal luminance homogeneity. The five-terminal device provides independent control terminals that enable precise adjustment of these capacitance parameters without increasing overall circuit complexity.
3Manufacturing precision
If manufacturing process fluctuations occur, then the threshold voltage varies, but conventional compensation methods cannot sufficiently eliminate the influence on conduction channel current
Solution Approach 1:
The five-terminal device configuration enables feedback control of the compensation capacitance. By independently controlling the capacitance parameters through additional terminals, the circuit can dynamically adjust compensation levels based on actual threshold voltage variations from manufacturing fluctuations. This feedback mechanism achieves better threshold voltage consistency without requiring overly complex compensation circuit structures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively adjusts luminance fluctuation by optimizing the correlation between coupling and storage capacitance values, resulting in improved display homogeneity and luminance stability, achieving better display effects.
Implementation Method 1
One end of the coupling capacitance is coupled to the output terminal of the driving transistor, the other end of the coupling capacitance is coupled to the control terminal of the driving transistor
Data Source
AI summary
A pixel driving circuit, a display panel and a display device. The pixel driving circuit includes a driving and compensation sub-circuit; a data writing sub-circuit; and a coupling capacitance. A ratio of a capacitance value of the coupling capacitance to the sum of the capacitance value of the coupling capacitance and the capacitance value of the storage capacitance is configured to be greater than a preset value. The preset value is determined based on the preset maximum luminance fluctuation of the display panel. In the present application, the luminance fluctuation is adjusted by adjusting the correlation relationship between the capacitance value of the coupling capacitance and the capacitance value of the storage capacitance. Thus, a new capacitance configuration is provided, the panel can be adjusted at a capacitance level, and a better display effect is provided.