Electronic Pen IC Variable Capacitance Resonant Frequency Tuning
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Solution Overview
Problem
The adjustment of resonant frequency in electronic circuits, such as those used in electronic pens, is cumbersome due to the need for trimmer capacitors, which complicates the optimization process and increases costs.
Innovation Solution
Incorporating a variable-capacitance capacitor within the IC, which allows for external connection and adjustment of the resonant frequency without the need for a trimmer capacitor, enabling automatic optimization of the resonant frequency through an external resonant frequency setting device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a trimmer capacitor is used to adjust resonant frequency, then the resonant frequency can be optimized, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the variable capacitance function directly into the IC by integrating a switch circuit that can connect or disconnect a capacitor based on control signals. This eliminates the need for a separate trimmer capacitor and reduces device complexity while maintaining the ability to adjust resonant frequency.
Solution Approach 2:
The patent replaces the mechanical adjustment mechanism of a trimmer capacitor with an electronic control system using a switch circuit controlled by digital signals from the IC. This substitution eliminates mechanical components and simplifies the overall device structure.
2Manufacturing precision
If a trimmer capacitor is used for resonant frequency adjustment, then frequency optimization is achieved, but production time and cost increase
Solution Approach 1:
The patent implements preliminary action by pre-programming the optimal capacitance values and corresponding control signals into the IC. During manufacturing, the system automatically selects and applies the appropriate control signal without requiring manual adjustment, thereby eliminating time-consuming trimmer capacitor adjustments and improving production efficiency.
Solution Approach 2:
The system performs self-service by automatically determining and applying the correct capacitance setting through internal control logic within the IC. This eliminates the need for external manual intervention in the frequency adjustment process, streamlining production.
3Device complexity
If a variable-capacitance capacitor is integrated within the IC, then device complexity is reduced, but the IC design and manufacturing become more complex
Solution Approach 1:
The patent applies segmentation by dividing the capacitor function into discrete controllable units within the IC. The switch circuit can selectively connect or disconnect the capacitor based on control signals, allowing the IC to present different capacitance values without requiring complex analog adjustment mechanisms. This modular approach simplifies integration while maintaining manufacturing feasibility.
4Manufacturing precision
If manual adjustment of trimmer capacitor is required, then resonant frequency can be optimized, but adjustment time and operational complexity increase
Solution Approach 1:
The system performs self-service by automatically determining and applying the correct capacitance setting through internal control logic within the IC. This eliminates the need for external manual intervention in the frequency adjustment process, streamlining production.
Solution Approach 2:
The patent implements feedback mechanisms where the system can detect the actual resonant frequency and automatically adjust the capacitance setting to achieve optimal performance. This closed-loop control eliminates manual tuning requirements and simplifies operation while maintaining precision.
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 solution simplifies the adjustment process, reduces costs by eliminating the need for trimmer capacitors, and ensures optimal resonant frequency settings for effective operation with position detecting sensors.
Implementation Method 1
The resonant circuit of the electronic pen is configured to have a resonant frequency f0 according to the frequency of the transmission signal and stores the electromagnetic energy based on an electromagnetic induction effect between the resonant circuit and the loop coils of the position detecting sensor
Implementation Method 2
The rectification circuit 205 that rectifies an induced current flowing in the resonant circuit 203 due to electromagnetic induction from the external and generates a supply voltage Vcc of the IC 230
Implementation Method 3
a variable-capacitance capacitor (trimmer capacitor) 204 for adjustment of the resonant frequency f0 is connected in parallel to the coil 201 and the capacitor 202. An adjuster adjusts the capacitance of this variable-capacitance capacitor 204 and thereby the resonant frequency f0 of the resonant circuit 203 is adjusted
Data Source
Figure 1
Figure 2
Figure 3A~4
AI summary
An electronic circuit of an electronic pen includes an integrated circuit, and a resonant circuit that is formed of a parallel circuit of a coil and a first capacitor and is externally connected to the integrated circuit. The integrated circuit includes a variable-capacitance circuit which, in operation, adjusts a frequency of the resonant circuit, and has a connection pin connecting the variable-capacitance circuit to outside of the integrated circuit. A first end of the parallel circuit is grounded and a second end of the parallel circuit is connected to a first end of a second capacitor externally connected to the integrated circuit. A second end of the second capacitor is connected to the connection pin of the integrated circuit and is connected to a diode which, in operation, clamps a potential of the second end of the second capacitor to a predetermined value.