Touch Panel Row Driving to Suppress EMI During Detection
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Solution Overview
Problem
Touch panels are susceptible to electromagnetic interference (EMI) from driving signals, which affects detection performance and can interfere with adjacent electronic devices.
Innovation Solution
A touch detection device with a sensor driving unit that applies pulse-shaped driving signals with varying frequencies to each row and adjusts frequencies based on EMI radiation levels, using frequency hopping and reverse voltage waveforms to reduce EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a driving signal is applied to the electrodes to enable touch detection, then touch detection capability is improved, but EMI radiation increases causing interference with adjacent electronic devices
Solution Approach 1:
The patent applies periodic pulse-shaped driving signals to the electrodes instead of continuous signals. By using periodic pulsing with controlled duty cycles and timing, the system maintains touch detection capability while reducing overall EMI radiation exposure time. The periodic nature allows for EMI suppression between pulses and enables frequency-based EMI management.
Solution Approach 2:
The patent dynamically adjusts driving signal parameters including frequency, amplitude, and pulse width based on detected EMI conditions. When EMI exceeds thresholds, the system changes operating parameters to reduce EMI radiation while maintaining functional touch detection. This includes adjusting the driving frequency away from resonant frequencies that amplify EMI.
2Productivity
If a high-frequency driving signal is used to improve detection speed, then productivity is improved, but EMI radiation intensity increases
Solution Approach 1:
The patent implements dynamic frequency adjustment where the driving signal frequency is not fixed but adapts based on real-time EMI monitoring and detection performance requirements. The system can switch between higher frequencies for fast detection and lower frequencies for EMI reduction, optimizing both productivity and EMI control dynamically during operation.
Solution Approach 2:
The system incorporates feedback mechanisms that monitor both touch detection performance and EMI radiation levels. Based on this feedback, the control unit adjusts driving signal parameters to maintain detection speed while preventing excessive EMI. The feedback loop ensures that productivity gains do not come at the cost of unacceptable EMI radiation.
3Device complexity
If the same driving frequency is applied to all rows to simplify control, then device complexity is reduced, but EMI peaks occur at specific frequencies causing interference
Solution Approach 1:
The patent divides the electrode array into multiple rows and assigns different driving frequencies to different rows. This segmentation approach distributes EMI energy across multiple frequencies rather than concentrating it at a single frequency, preventing strong EMI peaks. The multiplexer manages these segmented channels efficiently, maintaining acceptable control complexity while eliminating resonant EMI buildup.
Solution Approach 2:
Different regions (rows) of the electrode array are assigned different driving signal characteristics including frequency. This local differentiation ensures that no single frequency dominates the EMI spectrum. The multiplexer and control unit manage these locally optimized signals, achieving EMI suppression through frequency diversity while maintaining systematic control.
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
Effectively suppresses EMI by dispersing frequencies and canceling out EMI components, maintaining touch performance while reducing interference with adjacent devices.
Implementation Method 1
Electric current, which is movement of an electric charge, creates a magnetic field, and a moving magnetic field creates an electric current. An electrical conductor may act as an antenna for radio waves.
Implementation Method 2
When an amount of EMI radiation of a specific connection line to which the driving signal is applied is greater than or equal to a threshold, the sensor driving unit applies a signal of a reverse voltage waveform to an electrode of one of rows adjacent to the specific row.
Data Source
AI summary
A touch detection device includes a panel including a plurality of electrodes regularly arranged in rows and columns, a multiplexer connected to electrodes arranged in a specific column through connection lines and configured to form a sensing channel by connecting the plurality of electrodes in a row or a column, and a sensor driving unit operably coupled to the multiplexer and configured to perform a control operation so that a driving signal of a voltage waveform of a specific cycle is applied to the electrodes. The sensor driving unit applies pulse-shaped driving signals having different driving frequencies to each specific row.