Current Output Unit for Display Device with Time-Division Multiplexing
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Solution Overview
Problem
Conventional display devices using organic luminous elements face challenges in achieving uniform gradation display due to fluctuations in transistor characteristics, leading to inefficiencies in current output and increased circuit size, which results in higher costs and larger chip areas.
Innovation Solution
A display device with a reference current output unit generating adjusted currents for each luminescent color, plural current output units converting these currents based on gradation data, and a selector unit switching the output destination to respective pixel columns, allowing for efficient current control and reduced circuit size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If voltage drive mode is used with voltage-to-current conversion in each pixel, then gradation control can be achieved, but transistor characteristic fluctuations cause luminance unevenness and require larger circuit size
Solution Approach 1:
The patent merges multiple current output functions into a single current output unit by using time-division multiplexing. The unit sequentially outputs currents for different pixel columns within one horizontal scanning period, eliminating the need for separate current output circuits for each pixel column and reducing overall circuit size while maintaining current drive mode advantages
Solution Approach 2:
The patent implements dynamic switching of output destinations within the current output unit using switching elements controlled by selection signals. This allows the single current output unit to dynamically redirect current to different pixel columns based on the scanning sequence, enabling flexible current distribution without requiring static dedicated circuits for each column
2Device complexity
If current drive mode with single current output unit is used, then circuit size is reduced, but current control for multiple pixel columns must be achieved through time-division multiplexing
Solution Approach 1:
The patent employs periodic time-division multiplexing where the current output unit operates in sequential cycles within each horizontal scanning period. During each cycle, the unit outputs current to a specific pixel column in accordance with the scanning sequence, ensuring that all pixel columns receive their required currents systematically without interference
Solution Approach 2:
The current output unit generates multiple current copies for different pixel columns by sequentially replicating the current output function for each column during the horizontal scanning period. This allows a single physical unit to serve multiple destinations through temporal copying of its output function
3Ease of operation
If separate current output units are provided for each pixel column, then current control is simplified, but chip area and manufacturing cost increase
Solution Approach 1:
The patent designs the current output unit as a universal multi-functional circuit that can output currents to multiple pixel columns sequentially. By making the unit multi-functional rather than dedicated to a single column, the chip area is significantly reduced while the unit maintains the ability to control current to any required pixel column through switching mechanisms
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 solution enables a compact, low-cost display device with uniform gradation display by efficiently controlling current output to each pixel, minimizing transistor count and chip area while maintaining high luminance and chromaticity accuracy.
Implementation Method 1
The electrons and the holes are recombined in the organic layer 12 in the course of the movement to generate excitons. Luminescence is observed in a process in which energy of the excitons is deactivated.
Data Source
AI summary
To provide a current output type semiconductor circuit and a display device which are capable of realizing a reduction in cost by reducing the number of output stages and reducing a chip area. A display device includes three reference current generating units which generate reference currents corresponding to three display colors and outputs the reference currents, a selector which outputs an optimum reference current among the outputs of the three reference current generating units according to a display color of display data in response to a changing display color switching signal, a current output unit which outputs a current corresponding to a value of the display data with respect to a current per one gradation determined by the reference currents, and a selector for distributing the output of the current output unit to respective source signal lines corresponding to the display color.