Resonant Coil Q-Value Detection for Stylus Attachment Sensing
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Solution Overview
Problem
Conventional methods for detecting the in-position status of a stylus in electronic devices, such as tablet computers, often require large and costly detection assemblies, including Hall elements, which occupy significant space and increase production costs.
Innovation Solution
An electronic device equipped with an inverter circuit, resonance circuit, resonant capacitor adjustment circuit, and Q value detection circuit, where the resonant capacitor adjustment circuit increases the capacitance value during Q value detection to slow down oscillation attenuation, allowing accurate detection of the stylus's presence by controlling the connection of capacitors in parallel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Hall element detection assembly is used to detect stylus in-position status, then the detection reliability is improved, but the device volume and manufacturing cost increase
Solution Approach 1:
The patent extracts the detection function from the traditional Hall element assembly and relocates it to the wireless charging coil system. By utilizing the existing wireless charging coil and its resonant circuit, the stylus detection function is integrated into the charging mechanism, eliminating the need for separate Hall elements, soft boards, and spring sheets, thereby significantly reducing the detection assembly volume while maintaining detection reliability
Solution Approach 2:
The wireless charging coil is assigned multiple functions: it serves both as the electromagnetic induction component for wireless charging and as the detection sensor for stylus in-position status. By monitoring changes in the resonant frequency and Q value of the coil, the system can detect stylus presence without requiring dedicated detection components, thus achieving multi-functionality and reducing overall device complexity
2Reliability
If a Hall element detection assembly is used to detect stylus in-position status, then the detection reliability is improved, but the manufacturing cost increases
Solution Approach 1:
The wireless charging coil performs dual functions as both the charging component and the detection sensor. By monitoring the resonant frequency and Q value changes of the coil, the system detects stylus presence using the same component intended for charging, thereby eliminating the need for separate Hall elements and reducing manufacturing costs
Solution Approach 2:
The wireless charging coil monitors its own operational parameters (resonant frequency and Q value) to detect stylus presence. This self-diagnostic capability allows the charging component to simultaneously serve as the detection sensor, eliminating the need for external detection assemblies and reducing overall manufacturing costs
3Measurement precision
If the resonant capacitor adjustment circuit increases capacitance value during Q value detection, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The resonant capacitor adjustment circuit dynamically changes the capacitance value based on the detection phase. During Q value detection, the circuit switches to a higher capacitance configuration to slow down oscillation attenuation and improve measurement precision. During normal charging operations, the circuit returns to its standard configuration. This dynamic adjustment allows the system to optimize detection accuracy only when needed, minimizing the impact on overall device complexity
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
Accurate detection of the stylus's position is achieved without the need for a Hall device, reducing production costs and ensuring wireless charging only occurs when the stylus is correctly attached.
Implementation Method 1
the oscillation circuit includes an excitation voltage source, a full-bridge circuit and an LC series circuit which are connected in series; the LC series circuit includes an inductor and a resonance capacitor which are connected in series, and the LC series circuit outputs a resonance voltage signal of damped oscillation
Implementation Method 2
the resonant capacitor adjustment circuit increases the capacitance value during Q value detection to slow down oscillation attenuation
Data Source
Figure 1A
Figure 1B
Figure 2~3
AI summary
This application provides an electronic device and a stylus in-position determining method and relates to the field of terminal technologies. The electronic device includes: an inverter circuit, a resonance circuit, a controller, a resonant capacitor adjustment circuit, and a Q value detection circuit, where the resonance circuit includes a first capacitor and a transmit coil that are connected in series; an output terminal of the inverter circuit is connected to the resonance circuit; the resonant capacitor adjustment circuit is connected to the resonance circuit; the Q value detection circuit is connected to the resonance circuit; the resonant capacitor adjustment circuit includes at least a second capacitor; when a Q value of the transmit coil is detected, the controller controls the resonant capacitor adjustment circuit to operate, so that the first capacitor and the second capacitor are connected in parallel; the Q value detection circuit is configured to obtain a voltage signal representing a Q value; and the controller obtains the Q value based on the voltage signal, and when the Q value is greater than a preset threshold, determines that a stylus is attached to the electronic device. The resonant capacitor adjustment circuit participates in operation during Q value detection. This increases a capacitance of an oscillating capacitor, reduces an oscillation attenuation speed, and accurately detects a Q value.