Touch Panel EMI Suppression via Inverse Phase Driving
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Solution Overview
Problem
Touch panels are susceptible to electromagnetic interference (EMI) due to driving signals, which affect detection performance and are exacerbated by increasing touch area and varying load characteristics across rows, leading to uneven EMI radiation.
Innovation Solution
A touch detection device that applies in-phase voltage waveforms and ground potentials to rows, along with inverse phase voltages, and adjusts the number of rows based on load characteristics to effectively cancel EMI radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If voltage alternating operations are performed on a large number of touch cells to increase touch area, then touch detection coverage is improved, but EMI radiation amount increases significantly
Solution Approach 1:
The patent segments the touch panel into multiple row groups, where each group contains a sensing row and adjacent drive rows. By controlling voltage alternating operations separately for each row group, the system reduces overall EMI radiation while maintaining comprehensive touch detection coverage across the entire panel area.
Solution Approach 2:
The patent applies preliminary anti-action by using drive rows with opposite phase voltages to cancel EMI radiation from sensing rows. Before the EMI can interfere with detection, the opposite phase signals are generated in advance to neutralize the harmful electromagnetic fields.
2Object-generated harmful factors
If drive signals are applied to adjacent rows to reduce EMI, then EMI radiation is suppressed, but detection precision may be affected due to EMI variations across different rows
Solution Approach 1:
The patent applies local quality by measuring and compensating for EMI characteristics specific to each row group. Since EMI varies across different rows due to load characteristics, the system performs separate measurements and applies row-specific compensation to maintain uniform detection precision across the entire panel.
Solution Approach 2:
The patent implements feedback by measuring actual EMI levels in each row group and using this information to adjust drive signal parameters. The measurement results are fed back to the control system, which then optimizes the voltage alternating operations to achieve both EMI suppression and high detection precision.
3Object-generated harmful factors
If different voltage waveforms are applied to different rows to compensate for load characteristics, then EMI radiation is balanced across rows, but device complexity increases
Solution Approach 1:
The patent applies dynamics by implementing an adaptive operation algorithm that adjusts voltage waveforms based on measured load characteristics. The system dynamically modifies drive signal parameters for each row group according to actual EMI measurements, allowing the panel to adapt to varying conditions without requiring complex fixed compensation circuits.
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 method significantly reduces EMI interference, maintains touch sensitivity, and compensates for varying EMI radiation across rows by applying tailored voltage patterns.
Implementation Method 1
An electric current, which is movement of electric charges, creates a magnetic field, and a moving magnetic field creates an electric current.
Implementation Method 2
applies a second driving signal having a reverse phase to a phase of the first driving signal to consecutive rows adjacent to the at least one row
Data Source
AI summary
A touch detection device includes a panel including a plurality of electrodes regularly arranged in rows and columns, and a sensor driver configured to perform a control operation so that a driving voltage having a waveform of a specific cycle is applied to the electrodes. The sensor driver applies a sensing signal to a specific row and apply a first driving signal to at least one row adjacent to the specific row, applies a second driving signal having a reverse phase to a phase of the first driving signal to consecutive rows adjacent to the at least one row, and applies a ground signal to a row immediately adjacent to the at least one row.