In-Cell Touch LCD Ghost Noise Detection Circuit
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Solution Overview
Problem
In liquid crystal display devices with integrated touch panels, the 'ghost' touch phenomenon occurs due to exogenous noise frequencies matching the integral multiple of the horizontal scanning frequency, leading to false touch detections and reduced detection accuracy.
Innovation Solution
The implementation of a detector circuit with an integrating circuit and a noise detection method that differentiates between actual touch signals and noise signals by adjusting the touch panel scanning voltage timing and using averaging filters to identify and filter out noise frequencies, thereby reducing the influence of fictional touch 'ghost' on touch detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the touch panel drive frequency is set equal to the horizontal scanning frequency, then display noise is avoided and false detection problem is improved, but when exogenous noise frequency matches integral multiple of horizontal scanning frequency, the integrating circuit induces false integration to generate ghost
Solution Approach 1:
A noise detection circuit is introduced as an intermediary component to detect exogenous noise before it reaches the integrating circuit. The noise detection circuit monitors the input signal and generates a noise detection signal that triggers a reset of the integrating circuit, preventing false integration and ghost generation while maintaining the synchronized drive frequency configuration
Solution Approach 2:
The system implements a feedback mechanism where the noise detection circuit continuously monitors the input signal and provides feedback to the integrating circuit. When noise is detected, the feedback signal resets the integrating circuit, creating a closed-loop control system that dynamically prevents ghost generation while maintaining reliable touch detection
2Measurement precision
If the integrating circuit continuously integrates detection signals, then touch detection sensitivity is maintained, but exogenous noise at integral multiple frequencies causes false integration and ghost
Solution Approach 1:
The integrating circuit operates in periodic cycles rather than continuously. A reset signal is generated periodically based on noise detection or timing control, clearing the integration accumulator at appropriate intervals. This periodic reset prevents accumulation of noise-induced false signals while maintaining detection sensitivity during active integration periods
Solution Approach 2:
The noise detection circuit serves as an intermediary between the detection electrode and integrating circuit. It monitors the raw detection signal for noise characteristics and generates reset signals to the integrating circuit when noise is detected, preventing false integration without affecting genuine touch signal detection
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
This approach effectively reduces the occurrence of false touch detections caused by noise, enhancing the accuracy of touch position detection in liquid crystal display devices with integrated touch panels by distinguishing between actual touch signals and noise signals.
Implementation Method 1
a liquid crystal display panel which includes: a liquid crystal panel...
Implementation Method 2
a touch detection electrode which outputs a detection signal... the detection signal is a signal obtained by synchronously detecting a change in capacity generated by approaching a conductor
Implementation Method 3
an electrostatic capacitance system that detects a change in capacity of a touched portion
Data Source
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AI summary
An in-cell type liquid crystal display device includes a first unit that detects whether a touch is present, or not, on the basis of a current flowing in a plurality of detection electrodes (RX) when a touch panel scanning voltage is applied to counter electrodes (21) of each of M (M≥2) divided blocks, and a second unit that detects noise on the basis of a current flowing in the plurality of detection electrodes (RX), assuming that an (M+1)th counter electrode is present for the counter electrodes (21) of each of the M divided blocks, and assuming that a touch panel scanning voltage synchronous with the touch panel scanning voltage applied to the counter electrodes (21) of each of the M divided blocks is applied to the (M+1)th counter electrode.