Touch Sensor Electrode Layout Using Mains-Frequency Detection
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Solution Overview
Problem
Existing surface-type capacitive sensors face challenges in reducing circuit cost and power consumption due to their method of detecting touch positions by applying alternating current voltage and capturing capacitance changes, which is difficult to further minimize.
Innovation Solution
A touch sensor design utilizing divided electrodes with high impedance connections and a control unit that extracts signals in the commercial power supply frequency band, eliminating the need for alternating current voltage and simplifying the detection process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a surface-type capacitive sensor uses alternating current voltage to generate electric field and detect capacitance changes, then touch position detection is achieved, but circuit cost and power consumption cannot be further reduced
Solution Approach 1:
The patent extracts and eliminates the alternating current voltage generation component from the sensor system. By using a static conductive layer without active voltage generation, the invention removes the power-consuming AC voltage source while maintaining touch detection capability through capacitance changes detected by the divided electrodes.
Solution Approach 2:
The conductive layer serves dual purposes: it acts as both the detection element and the reference potential source. The system uses the inherent capacitance of the conductive layer and finger interaction without requiring external AC voltage generation, making the system self-sufficient and reducing external circuit requirements.
2Measurement precision
If a surface-type capacitive sensor applies alternating current voltage to four corners to form uniform electric field, then touch position can be calculated, but circuit complexity and cost increase
Solution Approach 1:
The patent divides the detection conductor into multiple separate electrode portions (first, second, third, and fourth electrodes) that are electrically insulated from each other. This segmentation allows detection of capacitance changes at different locations without requiring complex AC voltage generation circuits, simplifying the overall circuit design while maintaining position detection accuracy.
Solution Approach 2:
Instead of applying AC voltage to generate an electric field and detect changes, the invention inverts the approach by using a static conductive layer and detecting capacitance changes directly through divided electrodes. This reversal eliminates the need for AC voltage generation circuits and their associated complexity.
3Measurement precision
If a surface-type capacitive sensor uses four electrodes to capture capacitance changes, then touch position detection is enabled, but manufacturing cost increases
Solution Approach 1:
The conductive layer serves multiple functions simultaneously: it acts as the detection element, the reference potential, and the conductive path for capacitance changes. This multi-functionality reduces the number of separate components needed, simplifying manufacturing and reducing costs while maintaining detection accuracy.
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 enables a low-cost and low-power consumption touch sensor capable of accurate touch position detection, unaffected by conductor non-uniformity and individual differences, with a simple configuration.
Implementation Method 1
When a finger touches the conductive layer, a weak current flows through the finger via a capacitance formed by the conductive layer and the finger
Implementation Method 2
an electromagnetic induction method, and the like are known
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A touch sensor that is manufactured at low cost and driven with low power consumption is disclosed. A touch sensor according to an aspect of the present invention includes: a first detection conductor made up of divided electrodes having a plurality of electrode portions electrically insulated from each other; a second detection conductor insulated from the first detection conductor or connected to the first detection conductor with high impedance with a resistance equal to or higher than 10 kΩ; and a control unit configured to extract a signal in a commercial power supply frequency band from a signal detected from the first detection conductor with the second detection conductor used as a reference potential, and detect a touch position using the signal in the commercial power supply frequency band.