Touch Event Processing Circuit Noise Cancellation
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Solution Overview
Problem
The increasing proximity of touch panels and display panels in thinner and lighter smartphones, such as foldable devices, leads to larger parasitic capacitance, causing significant noise interference and making touch event processing circuits more susceptible to errors.
Innovation Solution
A touch event processing circuit that utilizes the average signal from a plurality of receiving circuits to cancel noise interference, comprising operation amplifiers, current processing circuits, and touch event detection circuits, along with an average circuit that performs averaging operations on current signals to generate average current signals for noise cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the distance between touch panel and display panel is reduced to make smartphones thinner and lighter, then the device portability is improved, but parasitic capacitance increases causing noise interference
Solution Approach 1:
The patent uses the noise signal itself to cancel noise by performing average cancellation operations. The noise signal captured through multiple receiving circuits is processed to generate a noise reference signal, which is then subtracted from the original signal to eliminate the harmful noise component while preserving the touch event information.
2Measurement precision
If multiple receiving circuits are used to capture touch signals, then touch detection capability is improved, but noise interference increases due to parasitic capacitance
Solution Approach 1:
The patent combines signals from multiple receiving circuits and performs average cancellation operations on them. By merging the noise components present in multiple channels and processing them together through the average cancellation circuit, the system effectively eliminates common-mode noise while preserving the differential touch signal information.
Solution Approach 2:
The patent implements a feedback mechanism where the output of the average cancellation operation is fed back to generate a noise reference signal. This noise reference is then used in subsequent cancellation operations to further reduce noise, creating a closed-loop system that continuously improves signal quality.
3Measurement precision
If average cancellation operation is performed to cancel noise, then signal-to-noise ratio is improved, but mutual capacitance cancellation becomes necessary
Solution Approach 1:
The patent designs the average cancellation circuit to perform multiple functions: it cancels noise from parasitic capacitance and simultaneously handles mutual capacitance cancellation. By making the circuit universal in its noise cancellation capability, the patent avoids adding separate dedicated circuits for different types of interference, thus managing complexity while maintaining effectiveness.
Data Source
AI summary
A touch event processing circuit includes receiving circuits and an average circuit. Each of the receiving circuits includes an operation amplifier, a current processing circuit, and a touch event detection circuit. The operation amplifier receives an input signal from a touch panel, and outputs a first current signal and a second current signal. The current processing circuit processes the first current signal and the second current signal according to a first current average signal and a second current average signal, to generate a processed current signal. The touch event detection circuit detects a touch event according to the processed current signal. The average circuit receives first current signals and second current signals from the receiving circuits; performs an average operation upon the first current signals, to generate the first current average signal; and performs an average operation upon the second current signals, to generate the second current average signal.