Capacitance Detection Circuit with Discharging Compensation
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Solution Overview
Problem
Traditional methods for detecting capacitance changes in capacitive sensors are prone to malfunction due to noise interference, as they require multiple charge and discharge cycles and are sensitive to environmental conditions, leading to potential misdetection.
Innovation Solution
An apparatus that includes a pulse modulator to charge and discharge a capacitive sensor, a discharging compensator to adjust the voltage level of the discharging signal, and a detector to measure the discharging time, which reduces the number of charge/discharge cycles and enhances noise resistance by compensating the discharging signal and detecting changes based on a voltage threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional capacitance detection methods are used with multiple charge/discharge cycles, then measurement precision is improved, but reliability deteriorates due to noise interference and environmental sensitivity
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitive sensor a set number of times before actual measurement. This preliminary charging process stabilizes the sensor's electrical state and reduces the impact of initial conditions and environmental noise on the final measurement, thereby improving both precision and reliability
Solution Approach 2:
The patent implements feedback by measuring the discharging time of the capacitive sensor and using this information to determine capacitance changes. The system continuously monitors the discharging process and adjusts measurements based on the observed discharging characteristics, enabling noise-resistant detection of capacitance variations
2Measurement precision
If multiple charge/discharge cycles are performed, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs preliminary charging a set number of times before measurement to stabilize the sensor state. This preliminary action reduces the need for repeated measurement cycles, thereby improving precision while minimizing additional time consumption
Solution Approach 2:
The patent skips unnecessary repeated charge/discharge cycles by using the discharging time measurement method. Instead of performing multiple full charge/discharge cycles for each measurement, the system rushes through the process by measuring discharging characteristics after a single charge, significantly reducing detection time while maintaining precision
3Device complexity
If discharging voltage at specific time point is measured, then device complexity is reduced, but measurement precision deteriorates due to noise sensitivity
Solution Approach 1:
The patent replaces traditional voltage measurement at fixed time points with a time-based measurement approach. Instead of measuring voltage at a specific moment (which is noise-sensitive), the system measures the duration of the discharging process, which provides more robust capacitance change detection with comparable device complexity
Solution Approach 2:
The patent changes the measurement parameter from voltage at a fixed time point to discharging time duration. This parameter change transforms the measurement approach from a noise-sensitive instantaneous value to a more stable temporal characteristic, improving measurement precision while maintaining simple circuit implementation
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 apparatus effectively decreases the number of charge/discharge cycles and improves noise resistance, allowing for accurate detection of capacitance changes by averaging discharging times over a set number of cycles, thereby reducing misdetection and enhancing reliability.
Implementation Method 1
A pulse modulator outputs a charging signal including at least one pulse. A switch charges a capacitive sensor according to the charging signal
Implementation Method 2
A discharging compensator outputs a discharging delay signal by compensating a voltage level of the discharging signal during a falling period of the discharging signal
Implementation Method 3
A detector outputs a detection signal by detecting a region where the discharging delay signal has a voltage threshold. A controller detects the capacitance change by measuring a discharging time of the capacitive sensor according to the detection signal
Data Source
AI summary
An apparatus of detecting capacitance detects a capacitance change of a capacitive sensor. The apparatus includes a pulse modulator configured to output a charging signal including at least one pulse. A switch is configured to charge the capacitive sensor according to the charging signal and output a discharging signal from the capacitive sensor. A discharging compensator is configured to output a discharging delay signal by compensating a voltage level of the discharging signal during a falling period of the discharging signal. A detector is configured to output a detection signal by detecting a region where the discharging delay signal has a voltage threshold. A controller is configured to detect the capacitance change by measuring a discharging time of the capacitive sensor according to the detection signal.