Touch Sensor Differential Layout for LGM-Resistant Multi-Touch Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional touch screens face issues with detection errors due to signal cancellation and reduced precision when multiple signals are input simultaneously, and are affected by low ground mass (LGM) leading to inaccurate touch detection, especially in foldable devices.
Innovation Solution
A touch input device with a touch sensor that uses a frequency hopping method and includes dummy electrodes to detect touch signals asynchronously with display driving signals, and employs a differential circuit to subtract sensing signals, effectively mitigating interference from LGM and external noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a differential circuit is used to subtract sensing signals from multiple channels, then noise reduction is achieved, but signal cancellation occurs when signals from two channels are simultaneously input, resulting in detection errors
Solution Approach 1:
The receiving electrodes are divided into two separate groups: first receiving electrodes connected to first terminals for receiving first sensing signals, and second receiving electrodes connected to second terminals for receiving second sensing signals. This segmentation prevents signal cancellation by ensuring that simultaneous touches on different channels do not interfere with each other through differential subtraction.
Solution Approach 2:
Dummy electrodes are introduced as intermediary elements to compensate for low ground mass effects. These dummy electrodes are positioned adjacent to the receiving electrodes and connected to the same terminals, providing a reference that cancels out LGM-induced noise without causing signal cancellation of actual touch signals.
2Object-affected harmful factors
If the frequency of driving signals for display and touch screen are synchronized to reduce noise, then noise reduction is achieved, but precision of touch detection is lowered when noise is present in the corresponding frequency band, and frequency change becomes impossible
Solution Approach 1:
The touch driving signal frequency is made dynamic and adjustable rather than fixed at a synchronized frequency. The system can change the frequency of the touch driving signal independently from the display driving signal frequency, allowing optimization of touch detection precision by selecting frequencies that avoid noise bands while maintaining effective touch sensing.
3Ease of operation
If a touch sensor is mounted on a touch input device, then touch detection functionality is provided, but the touch sensor is affected by low ground mass due to floating, causing signals to disappear or split, resulting in inaccurate touch detection
Solution Approach 1:
Dummy electrodes serve as intermediary reference elements that are electrically connected to the same terminals as the receiving electrodes. These dummy electrodes experience the same low ground mass effects but do not receive direct touch signals, allowing their output to be used as a reference for canceling out LGM-induced noise while preserving actual touch signal integrity.
Solution Approach 2:
The system changes the electrical parameters (frequency, amplitude) of the driving signals applied to dummy electrodes and receiving electrodes to optimize the cancellation of LGM effects. By adjusting these parameters, the system can differentiate between noise caused by floating and actual touch signals, maintaining reliable detection even in out-folded states.
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 device accurately detects touch signals and multiple touches with high sensitivity even in LGM conditions, allowing reliable operation in out-folded states and during wireless charging.
Implementation Method 1
a plurality of receiving electrodes forming mutual capacitance with the plurality of driving electrodes
Implementation Method 2
the touch detector detects a touch input of an object by subtracting at least one second sensing signal output through at least one second terminal from at least one first sensing signal output through at least one first terminal
Data Source
AI summary
A touch input device according to an embodiment comprises: a touch sensor including a plurality of driving electrodes, a plurality of receiving electrodes forming mutual capacitance with the plurality of driving electrodes, and a plurality of receiving dummy electrodes not forming mutual capacitance with the plurality of driving electrodes; and a touch detector including a plurality of receivers composed of a plurality of first terminals for receiving a plurality of first sensing signals, and a plurality of second terminals for receiving a plurality of second sensing signals. The touch detector detects a touch input of an object by subtracting at least one second sensing signal output through at least one second terminal from at least one first sensing signal output through at least one first terminal of at least one receiver.