OLED Pixel Driving Circuit Threshold Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
OLED displays experience non-uniform brightness due to drift in threshold voltage of drive transistors over time, leading to deviations in electric current and reduced luminous efficiency, resulting in decreased display quality.
Innovation Solution
A pixel driving circuit comprising a data writing module, coupling writing module, storage capacitor, driving transistor, switch units, and reset module, which controls signal transmission and threshold compensation to maintain consistent brightness across pixels, eliminating the influence of threshold voltage on display uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If OLED displays use drive transistors to control electric current for luminescence, then the display can achieve active luminescence and fast response speed, but the threshold voltage of the drive transistor drifts over time causing non-uniform brightness
Solution Approach 1:
The patent applies preliminary action by performing threshold compensation before the actual display operation. The pixel circuit includes a compensation capacitor that stores the threshold voltage value of the drive transistor during a compensation phase, and then uses this stored value to compensate for threshold drift during subsequent display phases. This preliminary compensation action eliminates the harmful effect of threshold voltage drift on brightness uniformity.
2Device complexity
If the same data signal is applied to all pixels, then the circuit operation is simple, but threshold voltage drift causes electric current deviation and non-uniform brightness
Solution Approach 1:
The patent applies local quality by making each pixel circuit self-adaptive through local threshold compensation. Each pixel's drive transistor has its own compensation capacitor that stores and compensates for its specific threshold voltage drift. This localized compensation approach maintains brightness uniformity without requiring complex global circuit modifications, as each pixel independently adjusts for its own threshold variations.
3Duration of action of stationary object
If OLED luminous efficiency degrades over time, then the display continues to operate, but brightness decreases under the same electric current
Solution Approach 1:
The patent applies feedback by implementing a compensation mechanism that measures and corrects for threshold voltage drift in real-time operation. The pixel circuit uses a feedback loop where the threshold voltage is compensated based on stored reference values, and this compensation is continuously applied to maintain stable electric current through the OLED. This feedback approach counteracts luminous efficiency degradation by adjusting the drive current to compensate for aging effects.
Data Source
AI summary
A display panel, a display device, a pixel driving circuit, and a control method for the pixel driving circuit. The pixel driving circuit includes a data writing module for transmitting signal of the data signal end to the first node in response to enable signal of the first control signal end; a coupling writing module for transmitting signal of the first power source voltage end to the first node in response to enable signal of the second control signal end; a storage capacitor; a driving transistor; a first switch unit; a second switch unit; a reset module for transmitting signal of the reset signal line to the fourth node in response to enable signal of the fifth control signal end; and a light emitting element, an anode thereof being electrically connected to the fourth node, an cathode thereof being electrically connected to a second power source voltage end.