Touch Sensing Panel Noise Reduction via Dynamic Mode Switching
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Solution Overview
Problem
Electronic devices with capacitive touch circuitry experience noise due to unintended capacitance between the touch sensor and display panel, causing interference during operations such as touch input and proximity sensing.
Innovation Solution
The electronic device employs a touch sensing panel with conductive lines arranged in a grid pattern, spaced apart from the display by an air gap, and alternates between self and mutual capacitive sensing schemes, along with modified detection schemes based on mode switching events, to reduce noise by adjusting driving signals and detection methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the touch sensor is positioned close to the display panel, then the device structure is compact and integration is improved, but unintended capacitance increases causing noise
Solution Approach 1:
A dielectric layer is introduced as an intermediary substance between the touch sensor and display panel. This dielectric layer has lower permittivity than air, which reduces the unintended capacitance coupling between the conductive lines of the touch sensor and the display panel, thereby reducing noise while maintaining compact structure.
Solution Approach 2:
The permittivity parameter of the medium between touch sensor and display panel is changed by using a dielectric layer with specific permittivity characteristics. This parameter change reduces the capacitance coupling strength, thereby reducing noise without requiring increased separation distance.
2Device complexity
If self-capacitive sensing is used, then circuit complexity is reduced, but noise from capacitance variation during proximity sensing increases
Solution Approach 1:
The sensing method is made dynamic by switching between self-capacitive and mutual-capacitive detection schemes based on operational mode. During proximity sensing, the system switches to mutual-capacitive mode which is less susceptible to noise from capacitance variation, while maintaining simpler self-capacitive mode for normal touch operation.
Solution Approach 2:
The detection scheme parameter is changed based on operational context. The system dynamically adjusts which capacitive sensing method is used by changing the driving signal configuration, selecting mutual-capacitive sensing during proximity events to reduce noise while maintaining circuit simplicity overall.
3Speed
If the touch sensor operates in close proximity to the display, then user interaction responsiveness is improved, but noise interference increases when eye is near the device
Solution Approach 1:
The touch sensor system dynamically adjusts its detection scheme based on proximity events. When the user's eye or face approaches the device, the system switches to mutual-capacitive detection mode which is more resistant to noise from nearby conductive objects, while maintaining fast response for normal touch interactions.
Solution Approach 2:
The system uses feedback from proximity sensing to dynamically adjust the touch detection mode. When proximity is detected (indicating eye is near), the system switches to a noise-resistant detection scheme, and returns to the original fast-response scheme when proximity ends, optimizing both speed and noise resistance based on real-time conditions.
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 noise interference, allowing for more accurate touch sensing and reduced signal noise when the user's eye is close to the device, enhancing user interaction and operational reliability.
Implementation Method 1
the first detection scheme detecting, independently, variations in capacitances of the plurality of first conductive lines and the plurality of second conductive lines
Implementation Method 2
a wireless communication circuit
Data Source
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Figure 3A
AI summary
According to an embodiment, a method for operating an electronic device may comprise operating touch circuitry configured to detect a touch or hovering according to a first driving signal in a first operation mode, detecting a first event related to mode switching, and operating the touch circuitry according to a second driving signal different from the first driving signal in a second operation mode based on detecting the first event. Other embodiments are also possible.