Variable Capacitance Circuit for Wearable Power Reception
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Solution Overview
Problem
Existing power reception devices face inefficiencies in non-contact power transmission due to frequency mismatches between resonance circuits and coil deformations, leading to reduced transmission efficiency, and current variable capacitor solutions result in discrete capacitance values and circuit upsizing.
Innovation Solution
A power reception device with a variable capacitance circuit comprising parallel-connected capacitors and switch control circuits that regulate the apparent capacitance value based on AC voltage fluctuations, allowing continuous frequency adjustment of the resonance circuit to match transmission signals, thereby improving efficiency without upsizing the circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable capacitor with multiple capacitors arranged in parallel is used to regulate capacitance value, then the resonance frequency can be adjusted to match transmission signals, but the capacitance value becomes discrete and cannot be regulated continuously
Solution Approach 1:
The patent applies the dynamics principle by using a switch connected to a capacitor that can be periodically turned on and off based on AC voltage fluctuations. This dynamic switching mechanism allows the circuit to achieve continuous apparent capacitance regulation rather than discrete fixed values, resolving the contradiction between frequency adjustment capability and capacitance value continuity.
2Manufacturing precision
If a mechanical variable capacitor is used to achieve continuous capacitance regulation, then the resonance frequency can be continuously adjusted, but the circuit size increases
Solution Approach 1:
The patent replaces the mechanical variable capacitor with an electronic switching mechanism. Instead of using a mechanical device that physically changes capacitance (which increases circuit size), the invention uses a switch controlled by AC voltage fluctuations to achieve the same continuous regulation effect, thereby reducing circuit size while maintaining capacitance continuity.
Solution Approach 2:
The patent employs periodic action by switching the capacitor on and off in response to AC voltage fluctuations. This periodic switching creates an effective continuous capacitance regulation without requiring a large mechanical variable capacitor, thus resolving the contradiction between continuous adjustment capability and compact circuit size.
3Adaptability or versatility
If the coil in the resonance circuit is deformed to fit a wearable device, then the device becomes flexible and wearable, but the inductance value fluctuates causing resonance frequency deviation
Solution Approach 1:
The patent applies feedback by using the AC voltage fluctuations (which reflect the actual resonance conditions) to control the switching of the capacitor. This feedback mechanism automatically compensates for inductance variations caused by coil deformation, maintaining stable resonance frequency despite the flexible wearable form factor.
Solution Approach 2:
The patent changes the capacitance parameter dynamically in response to AC voltage fluctuations caused by coil deformation. By adjusting the capacitance value through the switching mechanism based on these voltage changes, the system compensates for inductance variations and maintains stable resonance frequency in wearable applications.
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 solution enhances power transmission efficiency by continuously regulating the resonance frequency, compensating for frequency deviations and coil deformations, while maintaining a compact circuit design.
Implementation Method 1
the power transmission device and the power reception device have resonance circuits and electric power is transmitted via resonance phenomenon of these resonance circuits
Implementation Method 2
electric power is transmitted via resonance phenomenon of these resonance circuits
Data Source
AI summary
Provide are a power reception device, a wearable device, and a non-contact power feeding system that can improve the transmission efficiency while suppressing upsizing of the circuit thereof. A power reception device (3) includes a variable capacitance circuit (100) and a power reception coil (41) constituting a resonance circuit together with the variable capacitance circuit (100), in which the variable capacitance circuit (100) includes a first capacitor (C1) and a second capacitor (C2) connected in parallel to each other, a first switch (Tr1) connected in series to one end side of the first capacitor (C1), and a switch control circuit (110) that controls turning on and off of the first switch (Tr1) and includes a first comparator (OP1) that supplies a first control voltage to the first switch (Tr1) according to a comparison result between a reference voltage and an AC voltage applied to the second capacitor (C2).