Touch Capacitance Detection Circuit for Screen Noise Adaptation
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Solution Overview
Problem
Existing capacitance detection circuits in electronic devices are affected by screen noise, leading to reduced detection accuracy and potential 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 distinct periods to optimize signal-to-noise ratio and prevent saturation, by having a greater amplification factor during low noise periods and a smaller factor during high noise periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed high amplification factor is used to improve signal detection sensitivity, then the signal-to-noise ratio improves, but the amplification circuit becomes saturated during high noise periods
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), allowing the system to adapt to varying noise conditions and prevent saturation while maintaining detection sensitivity.
Solution Approach 2:
The amplification factor parameter is changed based on noise conditions. By switching between different amplification factors corresponding to different noise levels, the system optimizes the balance between signal detection accuracy and circuit stability under varying operating conditions.
2Reliability
If a fixed low amplification factor is used to prevent circuit saturation during high noise periods, then circuit stability is maintained, but the signal-to-noise ratio deteriorates during low noise periods
Solution Approach 1:
The amplification factor transitions from a fixed value to a dynamic parameter that adapts to noise conditions. During low noise periods, the control circuit selects the first amplification factor to maximize signal detection accuracy, while during high noise periods, it switches to the second amplification factor to maintain stability.
Solution Approach 2:
The system periodically adjusts the amplification factor based on the noise characteristics of different periods. By identifying low noise periods and high noise periods, the control circuit applies appropriate amplification factors during each period, optimizing performance throughout the operational cycle.
3Device complexity
If a single feedback resistor value is used to simplify the circuit design, then device complexity is reduced, but the system cannot adapt to varying noise conditions
Solution Approach 1:
The feedback resistor configuration is segmented into multiple discrete resistor values (first feedback resistor and second feedback resistor). Each resistor value is optimized for specific noise conditions, allowing the system to adapt to varying environments while maintaining a relatively simple circuit structure through selective switching.
Solution Approach 2:
The feedback resistor network serves multiple functions: it provides different amplification factors for different noise conditions, enables adaptability to varying environments, and maintains circuit stability. The same resistor network structure handles both low noise and high noise scenarios through controlled switching.
Data Source
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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 is configured to detect a capacitance of a capacitor to be detected, the capacitor to be detected is a capacitor for touch detection in a screen of an electronic device, and 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.