Sub-pixel Circuit with Dual Data Lines for OLED
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Solution Overview
Problem
Light emitting display devices face challenges in reducing circuit size per sub-pixel, making it difficult to increase display panel resolution or pixel integration due to the complexity of driving light emitting diodes with pulse amplitude modulation, which requires multiple transistors and increases circuit size.
Innovation Solution
A display device design that includes a sub-pixel with a constant current generator and a light emission period controller, using a scan write line, data lines, and driving voltage lines to apply driving current and control light emission periods, reducing the number of transistors needed and minimizing circuit size while maintaining gradation expression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pulse amplitude modulation (PAM) is used to drive light emitting diodes, then light emission control is achieved, but the number of transistors increases and circuit size increases
Solution Approach 1:
The patent divides the data signal into two separate data lines: one carrying data voltages for controlling current magnitude, and the other carrying control voltages for regulating light emission period. This segmentation allows independent optimization of each line's function, reducing the overall transistor count while maintaining precise light emission control through temporal and amplitude modulation separation.
2Ease of operation
If the number of transistors per sub-pixel is increased to enable PAM driving, then light emission control is improved, but pixel integration degree decreases
Solution Approach 1:
The patent implements multi-functional transistors that can operate in different modes depending on the signaling scheme. The same transistor structure serves both as a switch for light emission period control and as a current regulator, eliminating the need for dedicated transistors for each function and thereby increasing pixel integration density.
3Productivity
If the circuit size of each sub-pixel is reduced, then pixel integration degree increases, but light emission control capability may be compromised
Solution Approach 1:
The patent employs periodic control signals on the second data line to regulate the light emission period. By using time-domain modulation with periodic waveforms, the system achieves precise light emission control without requiring additional transistors, thus maintaining small sub-pixel circuit size while enabling high pixel integration.
Data Source
AI summary
A display device includes a scan write line for receiving a scan write signal, a first driving voltage line for receiving a first driving voltage, a first data line for receiving first data voltages, a second data line for receiving second data voltages, and a sub-pixel connected to the scan write line, the first data line, the second data line, and the first driving voltage line, wherein the sub-pixel includes a light emitting element connected to the first driving voltage line, a constant current generator configured to apply a driving current to the light emitting element according to a first data voltage among the first data voltages of the first data line, and a light emission period controller configured to control a light emission period of the light emitting element according to a second data voltage among the second data voltages of the second data line.