Touch Circuit Chip Noise Filtering via Impedance Matching
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Solution Overview
Problem
Conventional touch circuit chips generate incorrect comparison results due to noise interference, leading to incorrect determination of touch events on touch panels, necessitating the use of multiple filters to mitigate noise effects.
Innovation Solution
A touch circuit chip with a load adjustment unit and a comparator, where the comparator compares sensing signals with reference signals that have matching impedance values to the coupling capacitor, allowing for accurate determination of capacitance changes without the need for filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple filters are arranged in the touch circuit chip to avoid noise effects, then the reliability of touch detection is improved, but the device complexity increases
Solution Approach 1:
The patent extracts the noise component from the sensing signal by introducing a reference signal that contains the same noise but no touch information. The comparator then subtracts the reference signal from the sensing signal, removing the noise while preserving the touch-related capacitance change information. This eliminates the need for multiple filters.
Solution Approach 2:
The patent introduces a reference signal as an intermediary element that carries the noise component. This reference signal acts as a mediator between the noise source and the sensing signal, allowing the noise to be identified and removed through comparison without requiring complex filter circuits.
2Measurement precision
If filters are added to the touch circuit chip to mitigate noise, then the measurement precision of capacitance change is improved, but the device complexity increases
Solution Approach 1:
The patent extracts the noise component from the sensing signal through differential comparison with the reference signal. By subtracting the reference signal (which contains noise but no touch information) from the sensing signal, the noise is removed while the capacitance change information is preserved, achieving high measurement precision without complex filters.
Solution Approach 2:
The patent creates a copy of the noise component through the reference signal, which replicates the electrical characteristics and noise of the sensing path without including touch information. This copy is then used to cancel out the noise in the sensing signal through differential comparison, improving measurement precision without adding filter complexity.
3Measurement precision
If impedance matching is performed between the load and coupling capacitor, then the measurement precision of capacitance change is improved, but the device complexity increases
Solution Approach 1:
The patent adjusts the impedance parameter of the load (through adjustable resistance and capacitance values) to match the impedance of the coupling capacitor. This impedance matching optimizes the signal transfer and comparison characteristics, improving the precision of capacitance change detection while maintaining simple circuit architecture.
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 effectively filters out noise by matching noise components in both sensing and reference signals, enabling accurate detection of touch events on touch panels without the use of additional filters.
Implementation Method 1
a coupling capacitor Cm is formed at each of the intersecting points resulted by the intersection of the driving electrodes 101a ̃101e and the sensing electrodes 103a ̃103e
Data Source
AI summary
A touch circuit chip includes a load adjustment unit and a comparator. The load adjustment unit adjusts a determined impedance value according to an impedance matching signal. The first comparator has a first end electrically coupled to a first load and from which to receive a sensing signal, a second end electrically coupled to a second load via the load adjustment unit and from which to receive a reference signal, and an output end. The comparator compares the received sensing signal with the received reference signal and accordingly output a comparison result. The touch circuit chip determines whether there exists a change of a capacitance value of a coupling capacitor between the first and second loads according to the comparison result, wherein the determined impedance value is matched to the impedance value of the coupling capacitor and the first load. A touch apparatus is also provided.