Demultiplexer Initialization for OLED Charge Redistribution
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Solution Overview
Problem
Conventional organic light emitting display devices face challenges in maintaining high image quality due to charge redistribution caused by previous data voltage stored in parasitic capacitors, leading to poor image display and difficulty in implementing high-resolution panels.
Innovation Solution
The proposed solution involves setting the initialization power source to a voltage lower than the data signals, progressively turning on switches corresponding to control signals that overlap with scan signals, and using a demultiplexer to initialize other data lines to the initialization power source voltage during the data signal supply period, allowing data and scan signals to overlap, thereby ensuring efficient data supply to pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If data signals are supplied to data lines using conventional methods, then the display device can operate, but charge redistribution from previous data voltage stored in parasitic capacitors causes poor image quality
Solution Approach 1:
The patent applies preliminary action by initializing data lines to a reference voltage before data signals are supplied. The initialization circuit sets the potential of data lines to a predetermined level (e.g., ELVDD or ELVSS) prior to data signal input, preventing charge redistribution issues and ensuring high image quality from the start of each horizontal period.
Solution Approach 2:
The patent extracts the initialization function as a separate circuit component independent from the data driver. The initialization circuit is designed as a distinct module that can independently control the potential of data lines without interfering with the normal data signal supply operation, allowing the harmful charge redistribution to be eliminated while maintaining data signal integrity.
2Manufacturing precision
If the display device is designed for high resolution, then image quality improves, but parasitic capacitors cause charge redistribution that prevents achieving high resolution
Solution Approach 1:
For high-resolution displays, the patent implements preliminary initialization of all data lines before each frame or horizontal period. This ensures that even with increased pixel density and corresponding parasitic capacitance, each data line starts with a known potential, preventing the charge redistribution that would otherwise degrade image quality and limit achievable resolution.
3Manufacturing precision
If initialization voltage is supplied to all data lines continuously, then charge redistribution is prevented, but power consumption increases and data signal timing becomes complex
Solution Approach 1:
The patent implements periodic initialization where the initialization circuit operates only at specific intervals (e.g., at the beginning of each horizontal period or frame) rather than continuously. This periodic operation maintains image quality by preventing charge redistribution while significantly reducing power consumption compared to continuous initialization, and simplifies timing by coordinating initialization with the existing scan signal periodicity.
Data Source
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AI summary
An organic light emitting display device includes a scan driver progressively supplying a scan signal to scan lines, a data driver supplying data signals to output lines of the data driver during a period in which the scan signal is supplied, and demultiplexers respectively coupled to the output lines of the data driver, and supplying the data signals to data lines, each demultiplexer including first switches, each first switch being coupled between an output line of the data driver and a data line among a first set of data lines, and a second switch coupled between a first initialization power source and a data line among a second set of data lines, wherein the first set of data lines includes the second set of data lines and at least one other data line.