Capacitance Detection Circuit With Dynamic Gain Against Screen Noise
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Solution Overview
Problem
Capacitive sensors in electronic devices face interference from screen noise, leading to reduced detection accuracy due to saturation of amplification circuits.
Innovation Solution
A capacitance detection circuit with a control circuit that adjusts the amplification factor based on noise levels, using different feedback resistors in different periods to optimize signal-to-noise ratio, ensuring effective detection without saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed high amplification factor is used in the amplification circuit, then the signal-to-noise ratio for capacitance detection is improved, but the amplification circuit becomes saturated during periods of high screen noise
Solution Approach 1:
The amplification factor is made dynamic rather than fixed. The control circuit adjusts the amplification factor between a first amplification factor (during low-noise periods) and a second amplification factor (during high-noise periods) based on the screen noise level. This dynamic adjustment allows the system to maintain high detection precision when noise is low while preventing saturation when noise is high.
Solution Approach 2:
The amplification factor parameter is changed according to noise conditions. By switching between different amplification factors based on the screen noise level, the system optimizes the balance between signal-to-noise ratio and circuit stability, resolving the contradiction between measurement precision and reliability.
2Reliability
If a fixed low amplification factor is used to avoid saturation during high noise periods, then the amplification circuit stability is maintained, but the signal-to-noise ratio for capacitance detection deteriorates
Solution Approach 1:
The amplification factor dynamically adapts to noise conditions rather than remaining fixed at a low value. During low-noise periods, the system switches to a higher amplification factor to improve detection precision, while during high-noise periods it uses a lower amplification factor to maintain stability, thus resolving the contradiction between reliability and measurement precision.
Solution Approach 2:
The system periodically adjusts the amplification factor based on the scanning frequency of the screen and the corresponding noise levels. By synchronizing the amplification factor changes with the screen scanning periods, the system optimizes detection precision during low-noise intervals while preventing saturation during high-noise intervals.
3Measurement precision
If the amplification factor is increased to improve signal detection, then the capacitance detection precision is improved, but the influence of screen noise on detection results increases
Solution Approach 1:
The amplification factor parameter is adjusted based on screen noise levels. By using a higher amplification factor during low-noise periods and a lower amplification factor during high-noise periods, the system improves capacitance detection precision when possible while minimizing the amplification of screen noise when it is present.
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
Improves signal-to-noise ratio for capacitance detection, enhancing the performance of the capacitance detection circuit by adapting amplification factors to noise conditions, thereby reducing the impact of screen noise.
Implementation Method 1
detect a capacitance of a capacitor to be detected Cx
Implementation Method 2
an amplification circuit connected to the capacitor to be detected Cx, and configured to convert a capacitance signal of the capacitor to be detected Cx into a voltage signal
Data Source
AI summary
The present application provides a capacitance detection circuit, which could reduce the influence of screen noise on capacitance detection. The capacitance detection circuit includes: an amplification circuit connected to the capacitor to be detected, and configured to convert a capacitance signal of the capacitor to be detected into a voltage signal, the voltage signal being associated with the capacitance of the capacitor to be detected; and a control circuit connected to the amplification circuit, and configured to control an amplification factor of the amplification circuit to be a first amplification factor in a first period, and to control the amplification factor of the amplification circuit to be a second amplification factor in a second period, where noise generated by the screen in the first period is less than noise generated by the screen in the second period, and the first amplification factor is greater than the second amplification factor.