Active Matrix Display Voltage-Current Conversion Circuit Uniformity
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Solution Overview
Problem
The existing active matrix display devices using polysilicon TFTs for organic EL elements face challenges in achieving uniform voltage-current conversion characteristics, leading to deteriorated image quality due to variations in TFT characteristics, particularly in low temperature processing.
Innovation Solution
The implementation of multiple sets of voltage-current conversion circuits and output switching circuits that can be adjusted for each frame or line, allowing for frame switching, line switching, or combined frame and line switching to reduce variations in characteristics, thereby improving display uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If polysilicon TFTs are used for organic EL elements, then high resolution and medium to small display suitability are achieved, but uniform voltage-current conversion characteristics deteriorate due to TFT characteristic variations
Solution Approach 1:
The patent divides the voltage-current conversion function into multiple independent circuits (first and second voltage-current conversion circuits). Each circuit is responsible for converting voltage signals to current signals for driving organic EL elements. By segmenting the conversion function across multiple circuits with different TFTs, the patent reduces the impact of individual TFT characteristic variations on overall display uniformity.
Solution Approach 2:
The patent combines multiple voltage-current conversion circuits (first and second circuits) to work together in driving the display. The output signals from both circuits are merged to drive the organic EL elements, thereby combining their driving capabilities while averaging out the characteristic variations of individual TFTs, resulting in improved display uniformity.
2Ease of manufacture
If low temperature polysilicon processing is used, then manufacturing complexity is reduced, but voltage-current conversion characteristics become non-uniform
Solution Approach 1:
The patent segments the voltage-current conversion function across multiple circuits formed by low temperature polysilicon processing. By dividing the conversion function into first and second circuits with different TFTs, the patent reduces the impact of non-uniform characteristics inherent in low temperature processing, as each circuit's variations are averaged out when their outputs are combined.
Solution Approach 2:
The patent changes the operational parameters by using multiple conversion circuits with different TFT characteristics. Instead of relying on a single circuit with ideal characteristics, the system utilizes parameter variations across multiple circuits (formed by low temperature processing) to achieve overall uniformity through statistical averaging of their combined output.
3Reliability
If multiple voltage-current conversion circuits are implemented, then characteristic variations are reduced, but device complexity increases
Solution Approach 1:
The patent segments the voltage-current conversion function into multiple independent circuits, each handling a portion of the display driving task. This segmentation reduces characteristic variations by distributing the conversion load across different TFTs, and the modular structure allows for systematic integration that manages complexity.
Solution Approach 2:
The patent designs the multiple voltage-current conversion circuits to perform the same universal function of voltage-to-current conversion. Each circuit is structurally similar and interchangeable, which simplifies the overall design and integration process despite having multiple circuits, as they all serve the same purpose and can be manufactured using the same process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces variations in voltage-current conversion characteristics, enhancing the uniformity and quality of the display by alternately driving odd and even lines with different sets of voltage-current conversion circuits, resulting in improved image quality and reduced influence of circuit defects.
Implementation Method 1
a plurality of voltage-current conversion circuits for performing voltage-current conversion on an input video signal to supply a resultant current as a data signal to each pixel of a display array
Implementation Method 2
an organic EL element whose both electrodes are transparent or semi-transparent and which serves as a display element
Data Source
AI summary
To reduce variation in characteristics of a voltage-current conversion circuit for supplying a data signal to a data line for driving a transistor arranged in a pixel of an organic EL display device. Two sets A, B of voltage-current conversion circuits are provided in a data driver for driving a transistor arranged in a pixel, and RGB signals are supplied to these circuits. The voltage-current conversion circuits of sets A and B are controlled so as to be switched for every frame or every frame and line.