Capacitive Sensing Amplifier Dynamic Range Expansion
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Solution Overview
Problem
The dynamic range of capacitive sensing identification systems is limited by background capacitance, preventing effective amplification of capacitance changes, especially when the change amount is small compared to the absolute capacitance value, leading to reduced system performance.
Innovation Solution
A device and method that utilize an amplifier module with a feedback capacitor and a compensation module, which adjusts the input difference voltage and capacitance based on background capacitance to expand the dynamic range by canceling out the background capacitance effect, thereby preventing saturation and enhancing signal gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gain of the front-end detection circuit is increased to increase the effective dynamic range, then the effective dynamic range is improved, but the front-end detection circuit saturates due to background capacitance
Solution Approach 1:
The patent extracts the background capacitance component from the total capacitance signal by using a background capacitance storage capacitor to store the background capacitance value separately. This allows the detection circuit to process only the change amount of capacitance (touch signal) without being affected by the large background capacitance, thereby enabling higher gain amplification without saturation.
Solution Approach 2:
The patent introduces a background capacitance storage capacitor as an intermediary element that mediates between the sensing capacitor and the detection circuit. This intermediary stores the background capacitance value and enables the detection circuit to subtract it from the total capacitance, allowing the circuit to amplify only the relevant capacitance changes without saturation from the background capacitance.
2Measurement precision
If the gain is increased to amplify small capacitance changes, then the detection sensitivity is improved, but the dynamic range is reduced due to saturation
Solution Approach 1:
The patent extracts the background capacitance component from the total capacitance signal by using a background capacitance storage capacitor to store the background capacitance value separately. This allows the detection circuit to process only the change amount of capacitance (touch signal) without being affected by the large background capacitance, thereby enabling higher gain amplification without saturation.
Solution Approach 2:
The patent implements dynamic adjustment of the detection circuit's operating range by storing the background capacitance value and using it to dynamically offset the detection baseline. This allows the circuit to maintain optimal sensitivity for detecting small capacitance changes while preserving the ability to handle a wide range of capacitance values through adaptive biasing.
3Measurement precision
If the front-end detection circuit directly amplifies the capacitance change amount, then the effective dynamic range is improved, but the circuit saturates because the capacitance change is small compared to the absolute capacitance value
Solution Approach 1:
The patent extracts the background capacitance component from the total capacitance signal by using a background capacitance storage capacitor to store the background capacitance value separately. This allows the detection circuit to process only the change amount of capacitance (touch signal) without being affected by the large background capacitance, thereby enabling higher gain amplification without saturation.
Solution Approach 2:
The patent applies preliminary anti-action by pre-storing the background capacitance value in a storage capacitor before the actual detection process. This pre-stored value is then used to counteract or subtract from the total capacitance signal, preventing the harmful effect of background capacitance from causing saturation during amplification of small capacitance changes.
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 effectively adjusts the dynamic range of capacitive sensing systems, allowing for increased input signal amplification and improved detection of capacitance changes, enhancing system performance in applications like fingerprint identification and touchscreens.
Implementation Method 1
the principal of the capacitive sensing identification system is to convert a capacitance value into an electrical signal (for example, voltage, current, etc.) through a front-end detection circuit
Implementation Method 2
a front-end feedback capacitor being connected between the first input terminal and the output terminal of the amplifier module
Data Source
AI summary
Disclosed a device and a method for a capacitive sensing identification system. The device comprises: an amplifier module having a first input terminal, a second input terminal and an output terminal; an exciting signal source configured to provide an exciting signal to the first input terminal of the amplifier module through a sensing capacitor of the capacitive sensing identification system; a front-end feedback capacitor being connected between the first input terminal and the output terminal of the amplifier module; and a compensation module being connected between the second input terminal and the output terminal of the amplifier module and configured to provide an input difference voltage to the second input terminal of the amplifier module, receive an output voltage from the output terminal of the amplifier module, and adjust the input difference voltage provided to the second input terminal of the amplifier module in accordance with a background capacitance of the capacitive sensing identification system when the output voltage provided by the output terminal of the amplifier module is not within a predetermined range. The background capacitance is compensated using feedback mechanism, which can effectively adjust the effective dynamitic range of the capacitive sensing identification system.