Touch Panel Electrode Driving to Suppress Column EMI
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Solution Overview
Problem
Touch panels are susceptible to electromagnetic interference (EMI) due to the formation of electric and magnetic fields during voltage alternating current operations, which deteriorates detection performance, especially in larger panels with varying resistance and capacitance components leading to uneven EMI radiation.
Innovation Solution
A touch detection device with a sensor driving unit that applies driving signals with reverse voltage waveforms to adjacent electrodes, adjusting signal timing and slew rates based on connection line lengths to cancel out EMI components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the touch panel size increases to improve detection coverage, then the detection area is enlarged, but the EMI radiation varies significantly across sensing columns causing detection performance deterioration
Solution Approach 1:
The patent applies different driving strategies to different regions of the touch panel based on their EMI characteristics. Specifically, it identifies sensing columns with high EMI radiation and applies reverse voltage waveform driving only to those specific columns, while using conventional driving for other columns. This localized approach maintains detection performance across the entire large panel without unnecessarily complicating the driving of all columns.
Solution Approach 2:
The patent changes the driving signal parameters (voltage waveform characteristics) based on the EMI radiation levels of different sensing columns. By adjusting the voltage waveform to reverse polarity for high-EMI columns and maintaining conventional waveforms for low-EMI columns, the system optimizes detection performance across varying EMI conditions in different panel regions.
2Device complexity
If conventional driving signals are applied to all electrodes, then the circuit design is simple, but EMI radiation affects multiple sensing columns causing detection errors
Solution Approach 1:
Instead of applying uniform reverse voltage driving to all columns, the patent selectively applies this technique only to sensing columns that exhibit high EMI radiation. This localized application reduces the overall complexity of the driving circuit compared to a full reverse voltage implementation, while still effectively mitigating EMI issues in the problematic regions.
Solution Approach 2:
The patent converts the harmful EMI radiation into a useful indicator by monitoring which sensing columns exhibit high EMI levels. This information is then used to selectively apply reverse voltage driving only where needed, transforming the harmful EMI effect into a basis for optimized local compensation that reduces overall system complexity.
3Object-affected harmful factors
If reverse voltage waveform is applied to reduce EMI, then EMI radiation is suppressed, but the driving signal complexity increases
Solution Approach 1:
The patent applies reverse voltage waveform driving selectively only to sensing columns with high EMI radiation, rather than uniformly to all columns. This localized approach suppresses EMI where necessary while maintaining simple conventional driving signals in regions where EMI is not problematic, thereby minimizing the overall increase in driving signal complexity.
Solution Approach 2:
The patent applies reverse voltage driving partially - only to the extent necessary for columns exhibiting high EMI radiation. This partial application achieves sufficient EMI suppression for problematic columns without unnecessarily complicating the driving signals for all columns, optimizing the balance between EMI reduction and signal complexity.
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 reducing radiation deviations across sensing columns, enhancing detection performance in larger touch panels.
Implementation Method 1
A touch detection device with a sensor driving unit that applies driving signals with reverse voltage waveforms to adjacent rows, adjusting signal timing and slew rates based on connection line lengths to cancel out EMI
Implementation Method 2
an electric field and a magnetic field are formed due to the voltage alternating current operation, which generates EMI
Data Source
AI summary
A touch detection device includes a panel including a plurality of electrodes regularly arranged in rows and columns, a switch connected to electrodes arranged in a specific column through connection lines, and a sensor driving unit operably coupled to the switch 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. Lengths of the connection lines are differently set according to positions of electrodes arranged in a specific row. The sensor driving unit applies a second driving signal of a reverse voltage waveform to an electrode of one of two rows adjacent to the specific row when an amount of electromagnetic interference (EMI) radiation of a specific connection line to which the driving signal is applied is less than or equal to a threshold.