Capacitance Sensing Circuit With Noise-Phase Synchronized Input
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Solution Overview
Problem
Capacitive touch technology is susceptible to electromagnetic interference from nearby devices, such as liquid crystal display modules and charging modules, which affects the accuracy of touch event detection in capacitance sensing circuits.
Innovation Solution
A capacitance sensing circuit that generates an input signal based on the phase of noise using a phase detection unit, a phase calculation unit, and a waveform generator to minimize the energy associated with noise in the output signal, thereby reducing interference and enhancing detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a periodic input signal with specific frequency is applied to the detecting circuit, then the capacitance sensing circuit can calculate the change amount of the detection capacitor by analyzing phase or amplitude of the output signal, but the circuit becomes susceptible to electromagnetic interference of specific frequencies from surrounding devices
Solution Approach 1:
The patent applies dynamics by making the input signal frequency variable rather than fixed. The frequency of the input signal is dynamically adjusted to avoid frequencies that cause electromagnetic interference. The system determines an optimal frequency based on the operating conditions and adjusts the signal generator accordingly, transforming the static frequency approach into a dynamic adaptation mechanism that resolves the contradiction between measurement precision and interference susceptibility.
Solution Approach 2:
The patent implements parameter changes by modifying the frequency parameter of the input signal. Instead of using a fixed frequency, the system changes the frequency parameter based on detected interference conditions. This allows the capacitance sensing circuit to operate at frequencies that minimize electromagnetic interference while maintaining accurate touch event detection, directly addressing the technical contradiction.
2Object-affected harmful factors
If the input signal frequency is synchronized with signals from liquid crystal display module or charging module, then electromagnetic interference is reduced, but the device complexity increases due to additional synchronization mechanisms
Solution Approach 1:
The patent applies feedback by monitoring the electromagnetic environment and adjusting the input signal frequency accordingly. The system detects interference conditions and uses this feedback to determine the optimal operating frequency, creating a closed-loop control mechanism that reduces interference without requiring complex pre-synchronization with other devices. This feedback-based approach simplifies the overall system while effectively managing electromagnetic interference.
Solution Approach 2:
The capacitance sensing circuit performs self-service by autonomously determining and adjusting its own operating frequency based on detected interference conditions. Rather than requiring external synchronization signals from display or charging modules, the system independently adapts to the electromagnetic environment, reducing both device complexity and interference through self-directed frequency selection.
Data Source
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AI summary
An embodiment of the present disclosure is applied to the field of touch control technology, and provides a capacitance sensing circuit for sensing a detection capacitor of a detecting circuit, comprising: a capacitance judging circuit coupled to the detecting circuit for judging the capacitance of the detection capacitor according to the output signal; and an input signal generator coupled to the detecting circuit for generating the input signal according to noise, the input signal generator comprising: a phase detection unit for receiving the noise and detecting a first phase of the noise; a phase calculation unit coupled to the phase detection unit for receiving the noise and the first phase and calculating an optimum phase according to the noise and the first phase; and a first waveform generator coupled to the phase calculation unit for generating the input signal according to the optimum phase.