Touch Device Sensing Compensation Circuit Parasitic Impedance
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Solution Overview
Problem
Projected capacitive touch panels face signal delay and bandwidth limitations due to parasitic resistance and capacitance, leading to reduced sensitivity and signal-to-noise ratio (SNR) in touch units.
Innovation Solution
A touch device with a sensing compensation circuit that provides a negative input impedance to compensate for the impedance of the sense lines, enhancing the sensitivity for mutual capacitance sensing and increasing the signal-to-noise ratio by offsetting the bandwidth limitations caused by parasitic resistance and capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the touch panel uses conventional sense lines with parasitic resistance and capacitance, then the device can be manufactured with standard materials and processes, but the sensing speed and sensitivity are reduced due to signal delay and bandwidth limitation
Solution Approach 1:
The patent introduces a sensing compensation circuit as an intermediary component between the touch panel and the sensing system. This compensation circuit includes a compensation impedance (comprising resistance and capacitance) that mediates the signal transmission by offsetting the parasitic effects in the sense lines, thereby improving sensing speed without requiring fundamental changes to the touch panel structure
Solution Approach 2:
The patent modifies the electrical parameters of the sensing system by introducing adjustable compensation resistance and capacitance values. By changing these parameters to match the specific parasitic characteristics of different touch panel configurations, the system optimizes sensing speed and sensitivity while maintaining compatibility with standard manufacturing processes
2Measurement precision
If the sense lines have large parasitic resistance and capacitance, then the device can be manufactured with standard materials and processes, but the sensitivity for sensing mutual capacitance changes is reduced
Solution Approach 1:
The sensing compensation circuit acts as an intermediary that isolates the measurement process from the parasitic effects of the sense lines. The compensation impedance network mediates between the touch panel and the sensing amplifier, enabling accurate measurement of mutual capacitance changes despite the presence of parasitic resistance and capacitance in the sense lines
Solution Approach 2:
The patent implements a feedback mechanism where the sensing compensation circuit continuously monitors the signal characteristics and adjusts the compensation impedance accordingly. This feedback loop ensures that the compensation remains optimized for the current operating conditions, maintaining high sensing sensitivity while working with standard sense line configurations
3Reliability
If the parasitic resistance and capacitance are not compensated, then the device structure remains simple, but the signal-to-noise ratio of the sensing signal is decreased
Solution Approach 1:
The sensing compensation circuit serves as an intermediary signal processing stage that improves the signal-to-noise ratio before the signal reaches the final sensing amplifier. By placing the compensation impedance network in the signal path, the circuit enhances weak touch signals while suppressing noise and interference, thereby improving reliability without fundamentally altering the touch panel structure
Solution Approach 2:
The patent applies beforehand cushioning by pre-compensating for the expected parasitic effects in the sense lines. The compensation impedance is configured in advance to counteract the known parasitic resistance and capacitance, providing a buffer against signal degradation before it affects the measurement, thus improving signal-to-noise ratio while maintaining a relatively simple overall device structure
Data Source
AI summary
A touch device and a sensing compensation method are provided. The touch device may include a touch panel, a sensing compensation circuit and a sensing circuit. The sensing compensation circuit may be coupled to the touch panel for providing a compensation-impedance according to features of the touch panel. The sensing circuit may be coupled to the sensing compensation circuit. The sensing circuit receives touch information compensated by the sensing compensation circuit.