Resonant Stylus Pen Tip Circuit for Precise Touch Detection
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Solution Overview
Problem
Existing passive stylus pens face challenges in precise touch sensing due to noise interference and difficulty in signal transmission and reception, especially when used near conductive objects, and conventional capacitive resonance methods struggle with signal attenuation and require additional components like EMR sensors and ICs, limiting their effectiveness and cost.
Innovation Solution
A capacitive resonant stylus pen design with a resonance circuit including a ferrite core, coil, and capacitor, along with a conductive tip and blocking member, enhances signal transmission and reception, reduces noise interference, and allows for sophisticated touch recognition even near conductive objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passive stylus pen uses capacitive resonance method, then the stylus pen can transmit and receive signals through resonance with the touch sensor, but signal attenuation occurs and additional components like EMR sensors and ICs are required
Solution Approach 1:
The patent extracts the resonance circuit components (coil, capacitor, ferrite core) from the stylus pen body, positioning them at the tip area. This extraction allows the resonance function to be achieved with minimal components integrated into the stylus structure, eliminating the need for additional EMR sensors and ICs while maintaining signal transmission reliability
Solution Approach 2:
The touch sensor in the electronic device serves multiple functions: it acts as both the display interface and the resonance sensing element. The resonance circuit in the stylus pen universally interacts with the touch sensor's driving signal, allowing the same sensor infrastructure to support both capacitive touch and stylus resonance detection without requiring separate EMR sensing components
2Ease of operation
If the stylus pen touches the touch sensor near conductive objects, then touch input is possible, but the touch sensor fails to detect the stylus pen touch depending on conductive object location or touch area
Solution Approach 1:
The patent utilizes mechanical vibration principles through resonance. The stylus pen's resonance circuit vibrates at a specific resonant frequency when exposed to the touch sensor's driving signal. This resonant vibration creates a distinct signal pattern that can be detected even in the presence of conductive objects, allowing precise touch detection by identifying the unique resonance frequency signature rather than relying on general capacitive changes that are affected by conductive interference
Solution Approach 2:
The patent changes the detection parameter from general capacitive coupling to specific resonant frequency detection. By tuning the resonance circuit to a specific frequency and detecting the resonance signal at that frequency, the system can distinguish stylus touches from conductive object interference. The resonant frequency parameter serves as a unique identifier that remains stable even when conductive objects are present, enabling precise touch detection
3Reliability
If noise exists in a frequency band similar to the resonant frequency of the stylus pen, then the stylus pen can resonate with the driving signal, but the precision of touch sensing is greatly reduced
Solution Approach 1:
The patent implements feedback through the resonance detection mechanism. The touch sensor continuously monitors for resonance signals at the stylus pen's resonant frequency. When noise is detected in the frequency band, the system can adjust the driving signal frequency or amplitude to maintain resonance conditions, or filter out noise based on the expected resonance signal characteristics. This feedback loop ensures reliable resonance signal generation while maintaining touch sensing precision by dynamically adapting to noise conditions
Solution Approach 2:
The resonance circuit acts as an intermediary that filters and amplifies the desired signal while rejecting noise. By designing the resonance circuit with a specific quality factor (Q), the system creates a narrow bandwidth around the resonant frequency that naturally attenuates out-of-band noise. The resonance circuit mediates between the driving signal and the touch sensor, ensuring that only signals at the resonant frequency are strongly transmitted, thereby maintaining touch sensing precision even when noise exists in similar frequency bands
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 design improves touch sensing performance by generating a sufficient output signal, reducing noise, and enabling precise touch detection even when used near conductive objects, while being cost-effective and compatible with existing capacitive touch panels.
Implementation Method 1
the stylus pen generates a signal by resonating with a driving signal applied to the touch sensor
Implementation Method 2
A capacitive resonant stylus pen design with a resonance circuit including a ferrite core, coil, and capacitor
Data Source
AI summary
An electronic device according to an embodiment includes: a display panel; a touch electrode layer disposed on the display panel and comprising at least one touch electrode; and a conductive wire disposed on the display panel, disposed on the same layer as the touch electrode layer, and generating a magnetic field signal for driving a stylus pen.