OLED Pixel Circuit Segmentation for Brightness Uniformity
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Solution Overview
Problem
In OLED displays, variations in threshold voltages of drive transistors across different pixels lead to uneven brightness, affecting image quality, and increasing transistor density to mitigate this reduces the aperture ratio, which is disadvantageous for high-resolution displays.
Innovation Solution
A pixel circuit design with two pixel sub-circuits sharing a data line, scan lines, and a light-emitting control line, featuring a light-emitting control sub-circuit, node reset sub-circuit, drive control sub-circuit, write sub-circuit, and regulating sub-circuit, where the driving current is independent of the threshold voltage, ensuring uniform brightness across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If more transistors are arranged to decrease brightness difference, then display uniformity is improved, but aperture ratio decreases
Solution Approach 1:
The pixel circuit is divided into two independent pixel sub-circuits, each with its own drive transistor and light emitting device. Each sub-circuit independently controls brightness, allowing the system to compensate for threshold voltage variations without increasing the total transistor count per physical pixel, thus maintaining aperture ratio while improving display uniformity
Solution Approach 2:
The patent introduces a threshold voltage compensation mechanism that measures and compensates for Vth variations of drive transistors. By adjusting the gate voltage of the drive transistor based on the measured threshold voltage, the system compensates for transistor parameter variations, achieving uniform brightness without adding more transistors
2Reliability
If transistor density is increased to mitigate threshold voltage variations, then display quality is improved, but device complexity increases
Solution Approach 1:
By segmenting the pixel into two sub-circuits with independent drive transistors, the patent reduces the need for additional compensation transistors in each sub-circuit. This segmentation allows for simpler individual sub-circuit designs while achieving overall high display quality through the combined effect of both sub-circuits
Solution Approach 2:
The pixel sub-circuits are designed to be self-compensating through the threshold voltage compensation mechanism. Each sub-circuit independently measures and compensates for its own drive transistor's threshold voltage, eliminating the need for complex external compensation circuits and reducing overall device complexity
Data Source
AI summary
A pixel circuit, a driving method, a display panel and a display device. The pixel circuit includes: at least two pixel sub-circuits, a data line, a first scan line, a second scan line, a third scan line and a light-emitting control line. The pixel sub-circuit includes: a light-emitting control sub-circuit, a node reset sub-circuit, a drive control sub-circuit, a write sub-circuit and a light emitting device. The light-emitting control sub-circuit is configured to provide a signal provided by the first voltage signal end to a first node; the node reset sub-circuit is configured to form a conductive path between the first node and a second node; the write sub-circuit is configured to write a data signal provided by the data signal end and a threshold voltage to the second node; and the drive control sub-circuit is configured to drive the light emitting device to emit light.