LCD Noise Reduction via Segmented Power Supply Lines
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Solution Overview
Problem
Liquid crystal displays experience noise generation during polarity reversal drives due to switching between reference power supplies, which affects the operation margin of logic circuits and increases with the number of pixels, leading to decreased display quality.
Innovation Solution
The liquid crystal display incorporates an array substrate with auxiliary capacitive line driving circuits that alternately supply first and second auxiliary capacitive voltages, connected through specific supply lines, and a logic circuit with power supply lines, where certain lines are connected only at one end to minimize noise interference and stabilize voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polarity reversal drive is performed by switching between first reference power supply and second reference power supply frame by frame, then liquid crystal display can prevent liquid crystal burning, but noise occurs in auxiliary capacitive line during charging or discharging of pixels
Solution Approach 1:
The power supply system is segmented into two independent paths: one path supplies voltage to the auxiliary capacitive line, and the other path supplies voltage to the logic circuit. This segmentation prevents noise generated during polarity reversal from affecting the logic circuit, while still enabling the polarity reversal function to prevent liquid crystal burning.
Solution Approach 2:
A noise countermeasure unit is introduced as an intermediary component between the auxiliary capacitive line and the logic circuit. This unit includes a first power supply line for the auxiliary capacitive line and a second power supply line for the logic circuit, which are connected to different power supply terminals, thereby mediating the noise transmission path and protecting the logic circuit from noise.
2Manufacturing precision
If number of pixels is increased from QVGA to VGA or WVGA, then display resolution is improved, but noise is generated during writing into pixels due to coupling with auxiliary capacitive line
Solution Approach 1:
The power supply system is divided into separate paths for different functional blocks. The auxiliary capacitive line has its own dedicated power supply line (first power supply line) connected to a first power supply terminal, while the logic circuit has a separate power supply line (second power supply line) connected to a second power supply terminal. This segmentation isolates noise generated during high-resolution pixel writing from affecting the logic circuit operation.
3Extent of automation
If noise is generated in auxiliary capacitive line during polarity reversal, then operation margin of logic circuit is significantly decreased
Solution Approach 1:
The noise countermeasure unit acts as an intermediary that decouples the noise source (auxiliary capacitive line) from the sensitive component (logic circuit). By providing separate power supply lines connected to different power supply terminals, the intermediary structure prevents noise from decreasing the logic circuit's operation margin, while maintaining automated polarity reversal functionality.
Data Source
AI summary
A liquid crystal display includes an array substrate which includes a plurality of signal lines, a plurality of scanning lines, a plurality of auxiliary capacitive lines, a plurality of pixels, an auxiliary capacitive line driving circuit, a logic circuit, a first auxiliary capacitive voltage supply line, a second auxiliary capacitive voltage supply line, and a power supply line, an opposite substrate, and a liquid crystal layer. Each of the pixels includes a switching element, a pixel electrode, and an auxiliary capacitive element. A first common line and a second common line are connected to each other on one end side and are in a non-connected state in parts other than the part on the one end side. A common voltage is supplied to the first common line and the second common line from the one end side.