Organic Electroluminescent Display Device Using Demultiplexer and Auxiliary Capacitor
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Solution Overview
Problem
Conventional organic electroluminescent display devices require a large number of data driver output lines, increasing production costs as the resolution and size of the display region increase, and struggle to maintain uniform brightness due to the complexity of data signal distribution.
Innovation Solution
The use of demultiplexers to reduce the number of output lines in the data driver by sequentially supplying data voltages to multiple data lines, combined with storage and auxiliary capacitors to generate compensation voltages, allowing for efficient data signal distribution and uniform image brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of data driver output lines is increased to match the number of data lines, then data signal distribution is improved, but production cost increases due to more data ICs
Solution Approach 1:
The patent divides the data signal distribution function into multiple segments by introducing demultiplexers that sequentially supply data voltages to different data lines. Instead of requiring one data IC per data line, the system segments the output lines of the data driver and uses demultiplexers to distribute signals to multiple data lines, thereby reducing the number of data ICs needed while maintaining proper signal distribution.
2Ease of manufacture
If demultiplexers are used to reduce output lines, then production cost decreases, but voltage uniformity across data lines deteriorates
Solution Approach 1:
The patent introduces auxiliary capacitors connected to scan lines that provide feedback compensation for voltage variations. When scan signals are applied to scan lines, the auxiliary capacitors detect voltage changes and generate compensation voltages that are fed back to the storage capacitors, thereby maintaining uniform data voltages across all data lines despite the sequential supply method used by demultiplexers.
Solution Approach 2:
The patent changes the voltage parameters dynamically by using auxiliary capacitors to generate compensation voltages based on the scan signal levels. The compensation voltage adjusts the data voltage parameter in response to scan signal variations, ensuring that the actual voltage applied to each pixel remains uniform even though data voltages are supplied sequentially through demultiplexers.
3Ease of manufacture
If sequential data voltage supply is used, then the number of data ICs is reduced, but image brightness uniformity worsens
Solution Approach 1:
The auxiliary capacitors provide feedback compensation that ensures uniform image brightness. By detecting voltage variations caused by sequential data supply and generating appropriate compensation voltages, the system maintains consistent driving voltages for the OLEDs across all pixels, thereby ensuring uniform light emission and image brightness despite the reduced number of data ICs.
Data Source
AI summary
An organic electroluminescent display device employing a demultiplexer to reduce the number of output lines of a data driver. The display device uses the demultiplexer to store a data voltage in a data line, and supplies the stored data voltage to a pixel when a scan signal is applied, thereby displaying an image. Here, the data voltage supplied to the pixel is lowered because an electric charge is shared between a data line capacitor and a storage capacitor in the pixel. To compensate for the lowered data voltage, an auxiliary capacitor is provided for generating a compensation voltage. Here, the auxiliary capacitor increases the data voltage according to a level change of the scan signal. Therefore, a decrease in level of the voltage applied to the pixel is reduced or prevented so that DC/DC efficiency is enhanced without lowering a power supply voltage and a reference voltage.