Touch Display Signal Phasing for Electromagnetic Noise Cancellation
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Solution Overview
Problem
Touch display devices experience degraded touch accuracy due to electromagnetic wave noise emitted by surrounding electronic devices, which affects the performance of both the touch display device and the surrounding electronics.
Innovation Solution
A touch display device and touch sensing circuit are designed to improve resistance to electromagnetic noise by applying load-free driving signals with the same frequency as the touch driving signal but with a phase difference or amplitude difference, effectively lowering the cutoff frequency without adding a capacitor element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional touch driving signals are used, then touch display operation is maintained, but touch accuracy degrades due to electromagnetic wave noise from surrounding electronic devices
Solution Approach 1:
The patent applies preliminary anti-action by introducing a noise cancellation signal that has the same frequency as the electromagnetic wave noise but with a phase difference of 180 degrees. This cancellation signal is generated in advance and applied to the touch electrode before the noise fully impacts touch accuracy, thereby preemptively counteracting the harmful electromagnetic interference and maintaining measurement precision.
Solution Approach 2:
The patent converts the harmful electromagnetic wave noise into a beneficial effect by using the noise signal itself as the basis for generating the cancellation signal. The noise frequency is detected and utilized to create an opposing signal that neutralizes the interference, transforming the harmful factor into a useful reference for noise cancellation.
2Reliability
If a capacitor element is added to lower cutoff frequency for noise filtering, then electromagnetic noise resistance improves, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical/electrical approach of adding physical capacitor elements with a signal processing approach. Instead of modifying the hardware structure to achieve noise filtering, the invention uses electrical signal manipulation—generating and applying a cancellation signal with specific phase and frequency characteristics—to achieve the same noise resistance effect without increasing device complexity.
Solution Approach 2:
The patent achieves noise filtering by changing signal parameters (phase and frequency) rather than hardware parameters. The cancellation signal is configured with a phase difference of 180 degrees and matching frequency to the noise, allowing dynamic adjustment of noise cancellation effectiveness through parameter modification rather than physical component changes.
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 solution enhances touch accuracy by removing electromagnetic noise and reducing parasitic capacitance, thereby improving the overall performance and immunity to electromagnetic interference in touch display devices.
Implementation Method 1
a touch sensing circuit configured to output a pulse type touch driving signal to at least one of the plurality of touch electrodes
Implementation Method 2
capable of removing electromagnetic noise and increasing touch accuracy by lowering a cutoff frequency without adding a capacitor element
Data Source
AI summary
A touch display device includes a touch display panel including touch electrodes, display lines, and touch lines. A touch driving signal is configured to be applied to at least one touch electrode among the touch electrodes through at least one corresponding touch line among the touch lines during a touch period. A driving signal is configured to be applied to at least one of the display lines during the touch period. The driving signal has a same frequency as the touch driving signal and has a phase difference from the touch driving signal during at least a portion of the touch period.