Source Driver Impedance Adjustment for LCD Waterfall Defects
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Solution Overview
Problem
Liquid crystal display (LCD) devices experience uneven charging rates of pixel electrodes due to light exposure, leading to defects like waterfall patterns, which affect display quality and luminance.
Innovation Solution
A source driver with an impedance adjustment circuit that changes output impedance based on control signals, ensuring consistent charging rates by adjusting impedance in response to light conditions, using a combination of data conversion and impedance adjustment circuits with multiple impedance sub-circuits and switching transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the source driving circuit uses a fixed output impedance, then the circuit structure is simple, but the charging rate of pixel electrodes becomes uneven under different light conditions, causing waterfall defects
Solution Approach 1:
The patent applies dynamics by making the output impedance of the source driving circuit adjustable rather than fixed. The impedance adjustment circuit changes the output impedance based on control signals that correspond to different light conditions (illuminated vs. non-illuminated states). This dynamic adjustment ensures consistent charging rates across different display regions, eliminating waterfall defects while maintaining display quality.
Solution Approach 2:
The patent changes the electrical parameter (output impedance) of the source driving circuit based on operating conditions. By adjusting the output impedance parameter in response to light conditions, the circuit compensates for the uneven charging rates caused by light exposure, thereby eliminating waterfall defects and improving display reliability.
2Reliability
If the source driving circuit adjusts output impedance dynamically, then the charging rate consistency improves, but the circuit structure becomes complex with multiple impedance sub-circuits and switching transistors
Solution Approach 1:
The patent segments the impedance adjustment function into multiple independent sub-circuits, each responsible for a specific impedance level. The first impedance adjustment sub-circuit handles the illuminated state, while second impedance adjustment sub-circuits handle different non-illuminated states. This segmentation allows each sub-circuit to be relatively simple, and the control logic can selectively activate only the needed sub-circuit based on light conditions.
Solution Approach 2:
The impedance adjustment circuit is designed with multi-functionality to handle both illuminated and non-illuminated states through a unified control mechanism. The same control terminal receives control signals that determine which impedance sub-circuit to activate, making the overall system versatile while managing complexity through standardized control logic.
3Adaptability or versatility
If multiple impedance adjustment sub-circuits are used to handle different light states, then the adaptability to light conditions improves, but the number of control terminals and switching elements increases
Solution Approach 1:
The patent merges the control functions for different light states into a single control terminal. This control terminal receives control signals that encode both the light condition information and the impedance selection information. By combining these control functions, the patent reduces the number of separate control terminals needed while maintaining the ability to adapt to different light conditions through multiple impedance sub-circuits.
Data Source
AI summary
A source driver includes at least one data input terminal, a plurality of data output terminals, at least two control terminals and a plurality of source driving circuits. Each source driving circuit is connected to a data input terminal of the at least one data input terminal, a data output terminal of the plurality of data output terminals and the at least two control terminals. The source driving circuit is configured such that: the source driving circuit converts a format of a data signal from the data input terminal; and in response to one of different control signals that is received by all the at least two control terminals, the source driving circuit has a corresponding different output impedance, and transmits the converted data signal to the data output terminal.