Capacitance Detection Circuit Using Filtered Sample-and-Hold Signals
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitance detecting devices face reduced detection accuracy due to electromagnetic noise interference, which can lead to erroneous determination of capacitance changes.
Innovation Solution
Incorporation of a filter circuit and a sample-and-hold circuit that filters out specific frequencies and maintains a constant potential during switch-off, reducing noise influence and improving detection accuracy by stabilizing the potential before comparison.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitance detecting device uses simple switching circuits to detect capacitance changes, then the device complexity is low and ease of manufacture is high, but electromagnetic noise causes erroneous determination and detection accuracy deteriorates
Solution Approach 1:
The patent introduces a sample-and-hold circuit as an intermediary component between the switching circuit and the capacitance detection circuit. This sample-and-hold circuit captures the voltage signal at specific moments and holds it steady, acting as a mediator that isolates the detection circuit from electromagnetic noise caused by rapid switching operations. This allows accurate capacitance measurement without requiring complex noise filtering circuits.
Solution Approach 2:
The patent applies preliminary action by using the sample-and-hold circuit to capture and stabilize the voltage signal before it is processed by the capacitance detection circuit. By pre-stabilizing the signal and separating the sampling phase from the detection phase, the system eliminates noise interference in advance, enabling accurate measurement without complex real-time noise cancellation circuits.
2Productivity
If switching operations are performed rapidly to improve detection speed, then productivity increases, but electromagnetic noise increases causing erroneous determination
Solution Approach 1:
The sample-and-hold circuit serves as a temporal intermediary that decouples the rapid switching operations from the capacitance measurement process. It samples the voltage at precise moments during the switching cycle and holds this value steady for measurement, allowing fast switching to maintain detection speed while the held signal remains free from switching noise for accurate measurement.
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
Enhances detection accuracy by suppressing electromagnetic noise and stabilizing the potential, ensuring reliable capacitance change detection.
Implementation Method 1
a filter circuit that is connected to the connection node, transmits a potential of a frequency including switching frequencies of the second switch and the third switch, and does not transmit a potential of another specific frequency
Implementation Method 2
a sample-and-hold circuit that is connected between the filter circuit and the control circuit. The sample-and-hold circuit outputs a potential according to output of the filter circuit in a case where the second switch is controlled to be turned on, and holds and outputs a potential according to the output of the filter circuit obtained when the second switch is controlled to be turned off
Implementation Method 3
a first capacitor and a second capacitor that are connected in series to each other between a power source and a detection electrode
Data Source
Figure 1~2
AI summary
A capacitance detecting device includes: first and second capacitors (11, 12) connected in series to each other between a power source (V1) and a detection electrode (V2); first, second and third switches (SW1, SW2, SW3) connected between terminals of the first capacitor, between the first and second capacitors, and between terminals of the second capacitor, respectively; a control circuit (31) controlling to turn on/off the first, second and third switches, connected to a connection node between the first capacitor and the second switch, and detecting a change in a capacitance of the second capacitor; a filter circuit (40) connected to the connection node, transmitting a potential of a frequency including switching frequencies of the second and third switches, and not transmitting a potential of another specific frequency; and a sample-and-hold circuit (50) connected between the filter circuit and the control circuit.