Capacitive Touch Detecting Device Level Shift Noise Reduction
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Solution Overview
Problem
Conventional capacitive touch screen panels face challenges in minimizing noise interference from common electrodes and parasitic capacitances, making it difficult to reliably detect touch signals, especially when integrated into display devices like LCDs.
Innovation Solution
A capacitive touch detecting device that includes a sensor pattern spaced from a common electrode, a charging unit to supply charges, and a level shift detecting unit to identify voltage variations before and after a touch input, allowing for the acquisition of touch signals by detecting level shifts caused by touch inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a capacitive touch screen panel is integrated into a display device with a common electrode, then the touch detection function is added, but noise interference from the common electrode and parasitic capacitance increases, making it difficult to reliably detect touch signals
Solution Approach 1:
The sensor pattern is divided into multiple sensing electrodes arranged in a matrix, allowing independent detection of touch signals at different locations. This segmentation enables the system to distinguish between noise from the common electrode and actual touch signals by analyzing voltage changes at specific sensor nodes, thereby improving detection reliability while maintaining the integrated design.
Solution Approach 2:
A level shift detecting unit is introduced as an intermediary component between the sensor pattern and the control circuit. This unit specifically detects voltage level shifts caused by touch inputs and filters out noise from the common electrode and parasitic capacitance, enabling reliable touch signal detection in the integrated display structure.
2Length of stationary object
If the sensor pattern is placed close to the common electrode to reduce device thickness, then product thickness is reduced, but parasitic capacitance increases, interfering with touch signal detection
Solution Approach 1:
The level shift detecting unit serves as an intermediary that compensates for the increased parasitic capacitance effect. By detecting voltage level shifts rather than absolute voltage changes, the system can distinguish between parasitic capacitance effects and actual touch signals, allowing the sensor pattern to be placed closer to the common electrode without sacrificing detection accuracy.
Solution Approach 2:
The detection method changes from measuring absolute capacitance values to measuring voltage level shifts. This parameter change allows the system to operate effectively even with increased parasitic capacitance, as the level shift detection focuses on the dynamic change caused by touch inputs rather than the static parasitic capacitance background.
3Device complexity
If conventional capacitive touch detection methods are used, then the structure remains simple, but noise from the common electrode and parasitic capacitance make it difficult to recognize multiple touches and gestures
Solution Approach 1:
The sensor pattern is segmented into multiple sensing electrodes forming a matrix, enabling independent voltage measurements at each node. This segmentation provides sufficient spatial resolution to distinguish between multiple touch points and different gesture patterns, improving measurement precision while maintaining a relatively simple overall structure.
Solution Approach 2:
The level shift detecting unit acts as an intermediary that processes raw voltage signals from the sensor pattern and extracts meaningful touch information. By focusing on level shifts rather than absolute values, it enhances the precision of multi-touch and gesture recognition without significantly increasing structural complexity.
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 solution effectively minimizes noise interference and parasitic capacitance effects, enabling reliable touch signal detection and supporting multi-touch inputs and fine handwriting capabilities, while simplifying the manufacturing process and reducing product thickness.
Implementation Method 1
at least one sensor pattern which forms a touch capacitance between the touch input instrument and the sensor pattern, and which is disposed at a predetermined distance from a common electrode to thereby form a common electrode capacitance
Implementation Method 2
a charging unit for supplying a charge signal to the sensor pattern
Implementation Method 3
a level shift detecting unit for detecting a level shift which occurs in a voltage variation of the sensor pattern at the time of occurrence of a touch input, with respect to a voltage variation of the sensor pattern at the time of non-occurrence of a touch input
Data Source
AI summary
Provided is a touch detecting device that detects occurrence of a level shift phenomenon of a voltage variation to thus acquire a touch signal, when a touch capacitance due to a touch input is added to a common electrode capacitance formed between a common electrode and a sensor pattern. Accordingly, the touch signal may be stably obtained in spite of external noise, and an influence due to a parasitic capacitance may be minimized.