Display Device Ramp-Wave Correction for Uniform Pixel Luminance
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Solution Overview
Problem
Display devices experience luminance differences and streaks due to voltage drops in ramp wiring and pixel load capacitance, causing uneven brightness across pixels, especially when different luminance is displayed on the same horizontal line.
Innovation Solution
A display device with pixel circuits, signal lines, voltage output units, ramp wiring, voltage holding units, correction current sources, and a current adjustment unit that adjusts correction current based on voltage differences to maintain consistent luminance across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a ramp wave voltage is supplied to the ramp wiring connected to all pixels on one horizontal line, then the pixel circuits can be driven with signal voltage corresponding to luminance, but voltage drops due to wiring resistance and pixel load capacitance cause brightness differences and streaks on the display screen
Solution Approach 1:
The ramp wiring is divided into multiple segments by inserting correction current sources between adjacent voltage holding units. Each segment can have independent correction current applied to compensate for voltage drops, transforming the single long wiring path into multiple manageable sections with localized corrections.
Solution Approach 2:
Different correction currents are applied to different segments of the ramp wiring based on their specific voltage drop characteristics. The correction current amount is determined by the position and load conditions of each segment, allowing localized optimization of luminance uniformity rather than using a uniform correction approach.
2Manufacturing precision
If correction current is applied to compensate for voltage drops, then luminance uniformity improves, but the complexity of the ramp wiring structure increases
Solution Approach 1:
Correction current sources are introduced as intermediary components between the voltage holding units and the ramp wiring. These intermediaries provide the necessary correction current without requiring fundamental redesign of the ramp wiring architecture, thus improving luminance uniformity with minimal increase in structural complexity.
3Ease of operation
If the same correction current is supplied to all connection paths, then the control is simple, but luminance uniformity cannot be optimized for different positions on the ramp wiring
Solution Approach 1:
The correction current is made dynamic rather than static. The correction current amount is adjusted based on the position of the voltage holding unit and the specific luminance settings, allowing the system to adapt to different operating conditions. This dynamic adjustment enables optimization of luminance uniformity across different positions while maintaining manageable control through position-based rules.
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
The solution effectively reduces luminance differences and streaks by adjusting correction currents, ensuring uniform brightness across the display screen, even when different luminances are displayed on the same horizontal line.
Implementation Method 1
a plurality of voltage holding units that is connected between the ramp wiring and the plurality of signal lines, and holds the ramp wave voltage at a timing corresponding to luminance of the plurality of pixel circuits to generate the signal voltage
Implementation Method 2
a plurality of correction current sources that supplies correction current to a plurality of connection paths of the ramp wiring and the plurality of voltage holding units
Data Source
AI summary
Provided is a display device that includes a plurality of pixel circuits in a matrix, a plurality of data lines that supplies signal voltage corresponding to gradation to the plurality of pixel circuits, a ramp line, a voltage generator that supplies a ramp wave voltage to the ramp line. Display device further includes a plurality of first switches, each of the plurality of first switches having a first terminal electrically connected to the ramp line and a second terminal electrically connected to a corresponding one of the plurality of data lines. Display device further includes at least one correction current source that supplies a correction current to the first terminal of at least one of the plurality of first switches, and a controller including a comparator, the comparator having a first input terminal electrically connected to the ramp line and a second input terminal electrically connected to the ramp line.