Touch Event Processing Circuit Noise Cancellation via Signal Averaging
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Solution Overview
Problem
As cellphones become thinner and lighter, the proximity of touch panels to display panels increases parasitic capacitance, leading to significant noise interference in touch event processing circuits, making them more susceptible to noise interference and affecting signal detection.
Innovation Solution
A touch event processing circuit that utilizes multiple receiving circuits and an average circuit to cancel noise interference by performing an average operation on integrated voltage or current signals, thereby reducing noise and mutual capacitance, which improves the signal-to-noise ratio and ADC performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the touch panel is placed closer to the display panel to make cellphones thinner and lighter, then the device becomes more compact and portable, but the parasitic capacitance between the touch panel and display panel increases, causing significant noise interference in the touch event processing circuit
Solution Approach 1:
The touch event processing circuit is divided into multiple receiving circuits (first receiving circuit, second receiving circuit, etc.), each processing signals from different touch electrodes. This segmentation allows the system to independently process and average signals from multiple sources, effectively canceling noise interference while maintaining compact device design.
Solution Approach 2:
The patent combines signals from multiple receiving circuits through an averaging operation. The first receiving circuit processes a first signal from a first touch electrode, the second receiving circuit processes a second signal from a second touch electrode, and their results are averaged to generate a final touch event determination signal. This merging of multiple signal paths enhances noise cancellation capability.
2Measurement precision
If multiple receiving circuits are used to cancel noise interference through averaging, then the signal-to-noise ratio is improved and noise is canceled, but the device complexity and circuit structure become more complex
Solution Approach 1:
Multiple receiving circuits are designed with identical structures and functions, each capable of processing touch signals from different electrodes. This universal design allows the system to achieve noise cancellation through averaging while maintaining circuit simplicity and ease of manufacturing, as the same circuit design can be replicated multiple times.
Data Source
AI summary
A touch event processing circuit includes a plurality of receiving circuits and an average circuit. Each of the plurality of receiving circuits includes a first integrator circuit, a resistor, and a touch event detection circuit. The first integrator circuit is arranged to receive an input signal that includes a voltage sensing signal from a touch panel, and output a first integrated voltage signal. The resistor has a first terminal coupled to an output terminal of the first integrator circuit and a second terminal. The touch event detection circuit is arranged to detect a touch event according to the output from the second terminal of the resistor and a voltage average signal. The average circuit is arranged to: receive a plurality of first integrated voltage signals from the plurality of receiving circuits; and perform an average operation upon the plurality of first integrated voltage signals, to generate the voltage average signal.