Stylus Pen Variable Capacitor for Pressure Sensing
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Solution Overview
Problem
Existing stylus pens with variable capacitors face challenges in connecting the second electrode to a resonance circuit without increasing the pen's diameter, making it difficult to sense writing pressure effectively.
Innovation Solution
A stylus pen design that includes a conductive tip, a circuit portion, and a variable capacitor with a conductive body connecting the tip and the circuit portion, allowing the second electrode to be connected without a separate connection member, using a dielectric with a first and second surface and a conductive variable electrode whose contact area with the dielectric varies with pressure, enabling pressure-dependent capacitance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate connection member is used to connect the second electrode to the resonance circuit, then the connection reliability is improved, but the pen diameter increases
Solution Approach 1:
The patent merges the connection function into the variable capacitor structure itself. The second electrode of the variable capacitor is directly integrated with the resonance circuit, eliminating the need for separate connection members. This is achieved by configuring the variable capacitor such that its second electrode serves dual purposes: maintaining capacitance functionality and providing electrical connection to the resonance circuit, thereby reducing pen diameter while maintaining connection reliability
Solution Approach 2:
The second electrode of the variable capacitor is designed to perform multiple functions simultaneously: it maintains the capacitive function for pressure sensing and also serves as a connection element to the resonance circuit. This multi-functional design eliminates the need for dedicated connection members, resolving the contradiction between connection reliability and pen diameter
2Device complexity
If the two electrodes are arranged in the vertical direction of the pen, then the variable capacitor structure is simplified, but it becomes difficult to connect the electrode close to the front end to the resonance circuit
Solution Approach 1:
The patent transitions from a vertical arrangement to a horizontal arrangement of the two electrodes within the variable capacitor. By positioning the first and second electrodes side-by-side in a horizontal configuration rather than vertically stacked, the electrode close to the front end becomes accessible for connection to the resonance circuit while maintaining the simplicity of the variable capacitor structure
3Measurement precision
If the contact area between the conductive variable electrode and dielectric surface varies with pressure, then writing pressure sensing capability is improved, but the structural design becomes more complex
Solution Approach 1:
The patent utilizes parameter changes in the contact area between the conductive variable electrode and dielectric surface in response to applied pressure. As pressure varies, the contact area dynamically changes, which directly modulates the capacitance value. This parameter-based approach enables precise writing pressure sensing while avoiding complex mechanical structures, as the pressure information is extracted through electrical parameter variation rather than mechanical measurement
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
Enables the stylus pen to accurately sense writing pressure and position on a touch panel without increasing the pen's diameter, improving mechanical stability and assembly ease by eliminating the need for separate connection members.
Implementation Method 1
The variable capacitor may vary in capacitance according to the change in a distance between two electrodes or an area between the two electrodes
Implementation Method 2
The conductive case is isolated from the conductive body and electrically connected to a ground portion through capacitive coupling
Implementation Method 3
a conductive tip configured to receive an electric field transmission signal from at least one electrode of the touch panel
Data Source
AI summary
A stylus pen and a touch panel are provided. The stylus pen includes: a conductive tip configured to receive an electric field transmission signal from at least one electrode of the touch panel; a circuit portion configured to generate an electric field receiving signal corresponding to the received electric field transmission signal; a variable capacitor between the conductive tip and the circuit portion, and configured to vary the electric field receiving signal depending on a writing pressure applied to the conductive tip; and a conductive body outside the variable capacitor and electrically connecting the conductive tip and the circuit portion.