LCD Acoustic Noise Cancellation via Anti-Phase Transparent Electrode
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Solution Overview
Problem
Liquid crystal displays driven by alternating current (AC) type voltage signals generate audible noise due to the vibration of the common electrode, which becomes a significant issue as devices become thinner and the distance between the LCD and the portable device narrows, causing harsh sound recognition.
Innovation Solution
A liquid crystal display and driving method that incorporates a common electrode driving circuit and a first signal driving circuit, where the first signal has the same frequency and amplitude as the common voltage signal but is out of phase, applied to a transparent electrode on the opposite surface of the substrate, effectively canceling the audio frequency noise generated by the common voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AC type voltage signals are applied to drive the LCD, then the liquid crystal material reliability is improved, but audible noise is generated due to common electrode vibration
Solution Approach 1:
The patent applies the anti-phase signal to the transparent electrode, converting the harmful vibration caused by the common electrode into a beneficial cancellation effect. The anti-phase signal generates an opposite vibration that cancels out the original vibration, transforming the harmful audible noise into a useful vibration cancellation mechanism.
Solution Approach 2:
The patent changes the phase parameter of the signal applied to the transparent electrode, setting it to be out-of-phase (180 degrees) relative to the common electrode signal. This parameter change transforms the signal from one that would exacerbate vibration to one that cancels vibration, eliminating the audible noise while maintaining the driving function.
2Productivity
If the drive frequency of the common electrode is increased, then the display performance is improved, but the audible noise becomes more prominent
Solution Approach 1:
The patent converts the harmful high-frequency vibration into a beneficial cancellation effect by applying an anti-phase signal. The high-frequency drive signal that would normally cause prominent audible noise is instead used to generate the cancellation vibration, allowing high-frequency operation without noise.
Solution Approach 2:
The patent changes the phase parameter of the transparent electrode signal to be out-of-phase with the common electrode signal. This parameter change allows the system to operate at high frequencies while the opposite-phase vibration cancels the audible noise, decoupling display performance from noise generation.
3Length of moving object
If the thickness of the portable device is reduced, then the device becomes more compact, but the audible noise becomes more noticeable
Solution Approach 1:
The patent converts the harmful vibration into a beneficial cancellation effect, allowing thin device construction without noise. The anti-phase signal generates vibration that cancels the common electrode vibration, enabling compact device thickness while eliminating the audible noise that would otherwise be amplified in thin devices.
Solution Approach 2:
The patent changes the phase parameter of the transparent electrode signal to cancel the vibration caused by the common electrode. This parameter change eliminates the source of audible noise, allowing device thickness to be reduced without making the noise more noticeable, as the noise is canceled at its source.
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 removes the audible noise generated by the driving frequency of the common electrode, allowing for thinner portable devices without the harsh sound issue, while maintaining the reliability of the liquid crystal material and display performance.
Implementation Method 1
a first signal having the same frequency and amplitude as the common voltage signal and out of phase with the common voltage signal is applied to a transparent electrode
Data Source
AI summary
Disclosed is a liquid crystal display including a liquid crystal panel that includes a plurality of liquid crystal cells for controlling light transmission, a common electrode driving circuit for providing a common voltage signal to a common electrode provided in the liquid crystal panel and a first signal driving circuit for providing a first signal to a transparent electrode provided in the liquid crystal panel. The first signal and the common voltage signal have the same frequency and amplitude, but are out of phase with each other. The transparent electrode is designed to cancel an acoustic noise generated by the application of the common voltage signal. The liquid crystal panel includes two substrates that face each other. In one embodiment, the common electrode and the transparent electrode are formed in the same substrate, and in another embodiment, the common electrode and the transparent electrode are formed in different substrates.