Pixel Circuit Parasitic Capacitance Adjustment for Feeder Voltage Drop Compensation
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Solution Overview
Problem
Image display devices using organic electroluminescent elements suffer from luminance non-uniformity due to voltage drops in feeder lines, which affects the display quality and increases manufacturing costs when attempting to equalize voltage across all pixels.
Innovation Solution
The implementation of a pixel circuit configuration that includes a driving transistor, a threshold voltage detection transistor, a storage capacitor, and a switching transistor, along with parasitic capacitances and capacitors, allows for dynamic adjustment of capacitance and control voltages to compensate for voltage drops in feeder lines, thereby reducing luminance non-uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If feeder lines are used to supply power to multiple pixels, then device complexity is reduced, but luminance non-uniformity occurs due to voltage drops
Solution Approach 1:
The patent applies local quality by adjusting the parasitic capacitance values in switching portions of different pixels based on their specific positions and voltage drop characteristics. Each pixel's switching portion is customized with appropriate capacitance values to compensate for local voltage variations, achieving uniform luminance across the display while maintaining a simple shared feeder structure.
2Manufacturing precision
If feeder length or resistance is equalized for all pixels, then luminance uniformity is improved, but design flexibility is limited and manufacturing costs increase
Solution Approach 1:
The patent changes the electrical parameter (parasitic capacitance) of the switching portions to compensate for voltage drops in feeder lines of different lengths and resistances. By adjusting capacitance values rather than equalizing physical feeder dimensions, the patent maintains design flexibility while achieving luminance uniformity across pixels with varying feeder characteristics.
3Manufacturing precision
If parasitic capacitance is adjusted for each pixel, then luminance non-uniformity is reduced, but device complexity increases
Solution Approach 1:
The patent achieves equipotentiality in terms of luminance output by adjusting parasitic capacitance values to compensate for voltage drops. The switching portions are designed with specific capacitance values that equalize the effective voltage received by each pixel, creating uniform luminance across the display despite variations in feeder line characteristics.
Data Source
AI summary
An image display device includes a plurality of pixels, and feeders that commonly supply power to the plurality of pixels. In this image display device, each of the pixels has a light-emitting portion that emits light by a current supplied to the light-emitting portion, a driver that controls light emission of the light-emitting portion, and a switching portion electrically connected to the driver. The parasitic capacitance of the switching portion is determined with respect to each one pixel or one group of pixels according to the voltage drop of said feeder.