Touch Detection Circuit With Shielded Active Denoising
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Solution Overview
Problem
Capacitive detection devices face issues with noise interference leading to erroneous touch event detection due to insufficient capacitance variation, necessitating effective noise elimination methods.
Innovation Solution
A touch detection circuit equipped with an active denoising circuit that includes a shielding metal surrounding the driving trace, connected to a denoising circuit comprising resistors, capacitors, and capacitors to direct noise to ground, reducing interference and improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional capacitive detection is used without active denoising, then the device structure remains simple, but noise interference causes erroneous touch detection
Solution Approach 1:
A shielding metal layer is introduced as an intermediary component between the signal trace and the noisy environment. This shielding layer acts as a mediator that redirects noise signals to ground through dedicated noise detection terminals, preventing noise from interfering with the touch detection signal while maintaining circuit functionality
Solution Approach 2:
The detection circuit is segmented into distinct functional components: signal detection terminals for touch signals, noise detection terminals for noise signals, and a shielding metal layer. This segmentation allows independent handling of signal and noise paths, enabling effective noise cancellation without compromising the simplicity of the overall device structure
2Object-affected harmful factors
If shielding metal is added to reduce noise, then noise interference decreases, but manufacturing complexity increases
Solution Approach 1:
The shielding metal layer serves multiple functions simultaneously: it acts as an electromagnetic shield to block noise, provides a reference ground plane for signal stability, and can be integrated into existing PCB manufacturing processes. This multi-functionality reduces the need for additional specialized components and simplifies the overall manufacturing process
Solution Approach 2:
The shielding effect is achieved by controlling the electrical parameters of the shielding metal layer, such as its conductivity, thickness, and connection to ground terminals. By optimizing these parameters rather than adding complex structural elements, the design achieves effective noise reduction while maintaining ease of manufacture using standard PCB techniques
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 active denoising circuit effectively reduces noise interference, enhancing the accuracy of touch event detection by directing noise to ground and limiting current flow, thereby improving the reliability of capacitive touch detection.
Implementation Method 1
The third capacitor is connected between the third resistor and a driving trace, wherein the driving trace is configured to be connected to the load. The shielding metal is surrounding the driving trace.
Implementation Method 2
The first capacitor is connected between the first node and a ground voltage. The second capacitor is connected between the first node and the second node.
Data Source
AI summary
There is provided a denoising circuit connecting to two pins of a chip. The denoising circuit includes a shielding branch, a driving branch and an intermediate capacitor. The shielding branch is connected between a first pin of the chip, a ground voltage and a shielding metal. The driving branch is connected between a second pin of the chip and a load. The intermediate capacitor is connected between the shielding branch and the driving branch. The first pin and the second pin are used to respectively output a sinusoidal signal.