Touch Sensing Circuit Multifrequency Driving EMI Reduction
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Solution Overview
Problem
Conventional touch display devices experience increased electromagnetic interference (EMI) due to touch driving signals, which degrades system reliability and touch sensing performance, and can lead to parasitic capacitance issues during touch sensing.
Innovation Solution
The implementation of a touch sensing method and circuit that employs multifrequency driving signals to reduce EMI by varying the frequencies of touch driving signals based on the length or number of pulses in touch sections, thereby preventing parasitic capacitance and enhancing touch sensing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If touch driving signals with predetermined frequency are applied to touch electrodes for touch sensing, then touch sensing function is enabled, but electromagnetic interference (EMI) level increases
Solution Approach 1:
The patent applies dynamics by varying the frequency of touch driving signals dynamically across different touch sections rather than using a fixed frequency. The frequency is adjusted based on the length and position of touch sections, making the system adaptive and reducing EMI while maintaining touch sensing functionality.
Solution Approach 2:
The patent changes the frequency parameter of touch driving signals according to the characteristics of different touch sections. By modifying this key parameter based on section length and position, the system reduces electromagnetic interference while preserving accurate touch detection across the display panel.
2Measurement precision
If pulse signals with predetermined frequency are used for touch sensing, then touch coordinate detection is enabled, but EMI influence becomes more significant
Solution Approach 1:
The patent applies local quality by assigning different frequency characteristics to different touch sections based on their specific characteristics (length, position). Each touch section receives tailoring frequency parameters, which reduces EMI locally while maintaining measurement precision for touch coordinate detection in that specific region.
3Ease of operation
If conventional touch driving signals are applied, then touch sensing is performed, but parasitic capacitance occurs during touch sensing
Solution Approach 1:
The patent uses dynamic frequency adjustment to prevent parasitic capacitance formation. By continuously varying the frequency of touch driving signals according to touch section characteristics, the system avoids the resonant conditions that lead to parasitic capacitance, thereby maintaining ease of operation while eliminating this harmful effect.
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
This approach effectively minimizes EMI, maintains system reliability, and improves touch sensing performance by distributing electromagnetic interference and eliminating parasitic capacitance, ensuring consistent and accurate touch detection.
Implementation Method 1
capacitive touch sensing is commonly used to sense a touch and touch coordinates using a number of touch electrodes disposed on a touch panel (i.e. a touch screen panel) as touch sensors, based on changes in capacitance between touch electrodes or between a touch electrode and a pointer, such as a finger
Data Source
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AI summary
A touch sensing method, a touch sensing circuit, and a touch display device perform multifrequency touch driving by varying the frequencies (a, b) of touch driving signals (TDS) when sensing a touch or a touched position by outputting pulse-type touch driving by which one or more touch electrodes (TE) among a number of touch electrodes (TE) disposed on a display panel are driven sequentially. Undesired parasitic capacitance that would otherwise be caused by touch driving signals is prevented from occurring, and EMI influence is reduced.