Capacitance Measurement Apparatus With Adjustment Circuit
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Solution Overview
Problem
Conventional self-capacitance detection circuits in capacitive touch screens have a narrow effective signal range, making it difficult for subsequent signal processing due to the influence of reference capacitance.
Innovation Solution
A capacitance detection apparatus is designed with an adjustment circuit that cancels out the basic capacitance value of the channel capacitor, increasing the effective range of the output signal by using a reduced-basis element and switches to generate varying capacitance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional self-capacitance detection circuit is used, then the circuit structure is simple, but the effective signal range is too narrow
Solution Approach 1:
The patent segments the capacitance detection into two distinct parts: the basic capacitance value (reference capacitance) and the varying capacitance value (signal capacitance). By using the adjustment circuit to separately handle the basic capacitance value and the detection circuit to handle only the varying capacitance value, the system achieves better signal range without significantly increasing overall complexity.
Solution Approach 2:
The adjustment circuit serves as an intermediary component between the channel capacitor and the detection circuit. It processes the basic capacitance value first, transforming the capacitance signal before it reaches the detection circuit, thereby enabling the detection circuit to focus on detecting only the varying capacitance value with an optimized signal range.
2Ease of manufacture
If conventional detection method is used, then the circuit is easy to implement, but the output signal range is too narrow for subsequent signal processing
Solution Approach 1:
The adjustment circuit performs preliminary processing on the capacitance signal by canceling out the basic capacitance value before the signal reaches the detection circuit. This preliminary action prepares the signal in advance, ensuring that the detection circuit receives a pre-processed signal with an optimized dynamic range that is more suitable for subsequent signal processing operations.
3Measurement precision
If the basic capacitance value is not canceled, then the detection circuit can detect the total capacitance, but the effective signal range is limited
Solution Approach 1:
The adjustment circuit extracts and removes the basic capacitance value (reference capacitance) from the total capacitance signal. By taking out this constant component, the system leaves only the varying capacitance value for detection, which significantly increases the effective signal range while maintaining accurate detection of capacitance changes.
Data Source
AI summary
Provided is a capacitance measurement apparatus (200), including: a channel capacitor (101) configured to generate different capacitance values according to a sensing signal; a measurement circuit (220) connected to the channel capacitor (101) and configured to access a pulse signal and measure a capacitance value of the channel capacitor (101); and an adjustment circuit (210) connected between the channel capacitor (101) and the measurement circuit (220), and configured to cancel a basic capacitance value of the channel capacitor (101) and generate a varying capacitance value of the channel capacitor (101). The measurement circuit (220) is further configured to convert the varying capacitance value of the channel capacitor (101) into an output signal. A reference capacitance of the channel capacitor (101) is canceled by means of the adjustment circuit (210), thereby increasing the valid range of an output signal of the measurement circuit (220).