Demultiplexer Circuit Reduces Data Driver Complexity in OLED Displays
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Solution Overview
Problem
Conventional organic light emitting displays require a large number of data circuits in the data driver, leading to increased manufacturing costs and complexity, especially as the resolution and size of the image display portion increase, due to the need for multiple output lines to supply data signals to pixels.
Innovation Solution
The implementation of a demultiplexer system with transistors and capacitors connected between gate and drain terminals, allowing for sequential turning on of transistors and varying capacitor capacitances to reduce the number of output lines required in the data driver, thereby reducing manufacturing costs and ensuring uniform brightness across images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple output lines are used in the data driver to supply data signals to all data lines, then all pixels can be driven simultaneously, but the number of data circuits increases leading to higher manufacturing cost
Solution Approach 1:
The data driver output lines are segmented into multiple groups, with each group connected to a separate demultiplexer. Each demultiplexer further segments the data signals to multiple second data lines. This hierarchical segmentation reduces the number of output lines required in the data driver while maintaining comprehensive coverage of all data lines through sequential demultiplexing.
Solution Approach 2:
Demultiplexers are introduced as intermediary devices between the data driver output lines and the data lines. These demultiplexers receive data signals from reduced-number output lines and distribute them to multiple second data lines, acting as mediators that enable signal distribution with fewer source connections.
2Device complexity
If the number of data circuits is reduced by using fewer output lines, then manufacturing cost decreases, but uniform brightness across images becomes difficult to maintain
Solution Approach 1:
Capacitors are connected between gate and drain terminals of transistors in the demultiplexer to preliminarily store electrical charge. This preliminary energy storage compensates for voltage drops and timing variations during sequential data signal transmission, ensuring that pixels receive adequate drive signals regardless of their position in the scanning sequence, thereby maintaining uniform brightness.
Solution Approach 2:
The capacitance values of capacitors connected to different data lines are varied according to specific design criteria. By adjusting capacitor parameters (capacitance values), the circuit compensates for positional variations in pixels, ensuring that each pixel receives the appropriate charge to maintain uniform brightness across the display.
3Measurement precision
If resolution and size of the image display portion are increased, then display quality improves, but the number of required data circuits increases leading to higher manufacturing cost
Solution Approach 1:
The system transitions from a direct one-to-one mapping between data driver output lines and data lines to a multi-dimensional hierarchical structure. Data signals are first distributed along the row dimension through demultiplexers, then sequentially along the column dimension during scanning. This dimensional transformation enables high-resolution displays with fewer data driver output lines.
Solution Approach 2:
The display system employs periodic scanning action where data signals are sequentially supplied to different columns during different scanning periods. Combined with the demultiplexer structure, this periodic action enables high-resolution displays to be driven with fewer simultaneous output lines, as only one column is actively updated at each scanning period.
Data Source
AI summary
An organic light emitting display capable of reducing the manufacturing cost and displaying images with uniform brightness. The organic light emitting display includes: a data driver for supplying a plurality of data signals to a plurality of first data lines, respectively; an image display portion having a plurality of second data lines, a plurality of scan lines, and a plurality of pixels; and a demultiplexer having a plurality of data transistors arranged in the respective first data lines to supply the plurality of data signals supplied to the first data lines to the plurality of second data lines, and a plurality of capacitors connected between respective gate terminals of the plurality of data transistors and the second data lines.