Capacitive Touch Control Circuit Frequency Conversion
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Solution Overview
Problem
Conventional capacitive touch panels suffer from low signal-to-noise ratio (SNR) due to noise signals in the circuit environment, long integration times affecting frame rate, and occupy a larger chip area, increasing costs.
Innovation Solution
A control circuit comprising a signal-detecting circuit, intensity/frequency conversion unit, and frequency-analyzing unit, which converts intensity signals into frequency signals, analyzed to determine capacitance changes, reducing noise impact and chip area usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an integrator is used to integrate pulse signals from the capacitive touch panel, then the capacitive change can be accumulated into a processable voltage signal, but the integration time becomes long which affects the frame rate of the touch panel
Solution Approach 1:
The patent replaces the conventional integrator-based signal processing system with a frequency-based signal processing system. Instead of integrating pulse signals over time to accumulate charge into voltage, the invention uses a frequency generator to convert the capacitive change into frequency modulation of an output signal. This substitution eliminates the need for long integration times while maintaining detection precision, thereby resolving the contradiction between measurement precision and frame rate.
2Ease of operation
If an integrator, sampling and holding circuit, and ADC are used in the control circuit, then the capacitive touch panel can be controlled and read, but the chip area occupied becomes larger increasing the cost
Solution Approach 1:
The patent extracts and removes the complex components (integrator, sampling and holding circuit, ADC) from the control circuit, replacing them with a simplified frequency-based detection system. The core functionality of capacitive touch detection is preserved through frequency generation and analysis, while the unnecessary complex components are eliminated, thereby reducing chip area and cost while maintaining operational capability.
3Productivity
If conventional signal processing circuits are used in the control circuit, then the touch panel can be operated, but noise signals are integrated along with the signal resulting in low signal to noise ratio
Solution Approach 1:
The patent changes the parameter domain from time-domain integration to frequency-domain processing. By converting the capacitive change signal into frequency modulation, the system can operate continuously without long integration times, and frequency-based analysis provides inherent noise rejection capabilities. This parameter transformation allows the touch panel to operate effectively while maintaining high signal-to-noise ratio, as frequency analysis can distinguish signal from noise more effectively than time-domain integration.
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 achieves a high SNR, is not affected by noise, reduces chip area occupation, and lowers system costs while maintaining effective capacitance detection.
Implementation Method 1
a voltage controlled oscillator electrically connected with the signal-detecting circuit to convert an output signal of the signal-detecting circuit into a frequency signal
Data Source
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AI summary
The present invention relates to a control circuit and control method for detecting the capacitance of a touch panel. The control circuit comprises: a signal-detecting circuit for charging a sensing wire of the touch panel to obtain an intensity signal of the sensing wire; an intensity/frequency conversion unit for converting the intensity signal into a frequency signal, the frequency of which corresponds to the level of the intensity signal; and a frequency-analyzing unit for analyzing the frequency signal to obtain a signal amount of the corresponding sensing wire. The control circuit for the capacitive touch panel has a good SNR, which will not be affected or lowered by noise signals in the circuit environment, and is constituted of simple components to reduce the occupied area on the chip and lower the cost.