Display Driver Inter-Gradation Short Circuit for LCD Color Uniformity
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Solution Overview
Problem
In large-screen, high-definition liquid crystal display devices, signal delays due to wiring resistance and capacitance cause color unevenness between the center and edge regions, leading to visible gradation differences.
Innovation Solution
A display driver with a gradation voltage generation circuit applying voltages to intermediate portions of wiring lines, decoders selecting voltages based on pixel data, and inter-gradation short circuits to reduce delay times by short-circuiting wiring lines, ensuring uniform voltage levels across the display panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the horizontal scanning period is shortened to increase screen size and high definition, then productivity and resolution are improved, but signal delay increases causing color unevenness between center and edge regions
Solution Approach 1:
The inter-gradation short circuit performs preliminary action by pre-charging the wiring lines before the actual signal transmission. This advance preparation reduces the delay time for far-end DAC circuits, ensuring that voltage levels reach desired levels before the horizontal scanning period ends, thereby preventing color unevenness while maintaining high definition and large screen size
Solution Approach 2:
The invention changes the timing parameter by introducing a preliminary charging phase before signal transmission. By controlling the inter-gradation short circuit to operate at specific timing (before the horizontal scanning period), it alters the voltage level trajectory, ensuring uniform voltage levels across the display panel without sacrificing productivity
2Adaptability or versatility
If the wiring length between gradation voltage generation circuit and DAC circuit is increased, then more DAC circuits can be disposed (improving device functionality), but delay time increases causing level difference
Solution Approach 1:
The inter-gradation short circuit applies preliminary action by pre-charging the wiring lines before signal transmission. This advance charging compensates for the delay caused by long wiring, ensuring that even far-end DAC circuits receive properly timed signals. This allows more DAC circuits to be disposed along the wiring lines without suffering from excessive delay time
Solution Approach 2:
The inter-gradation short circuit acts as an intermediary mechanism between the gradation voltage generation circuit and the DAC circuits. It mediates the signal transmission by providing preliminary charging, thereby reducing the harmful effect of long wiring length on delay time while maintaining the ability to dispose multiple DAC circuits
Data Source
AI summary
The disclosure includes bus wiring constituted by wiring lines; a gradation voltage generation circuit that generates M gradation voltages representing brightness levels with M gradations, and applies the M gradation voltages to an intermediate portion on M wiring lines belonging to the bus wiring; a plurality of decoders, each of which receives M gradation voltages via the M wiring lines and selects one of the M gradation voltages according to the pixel data pieces to output the selected gradation voltage; a plurality of output amplifiers that individually amplifies the voltages output from the plurality of decoders and generates the amplified voltages as the plurality of pixel drive voltages; and first and second inter-gradation short circuits that short-circuit one ends of each of the M wiring lines and the other ends of each of the M wiring lines according to a load signal for capturing the pixel data pieces.