Variable Capacitor Resonance Tuning for Wireless Power Transfer
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Solution Overview
Problem
In contactless electric power feeding systems using the resonance method, efficiency deteriorates when the distance between the transmitting and receiving apparatus changes, due to variations in space impedance and resonance frequency.
Innovation Solution
A contactless electric power feeding system with self-resonant coils and variable capacitors, where controllers adjust capacitance to maintain optimal resonance frequency and efficiency, using a combination of fixed and variable capacitors to synchronize capacitance changes between the transmitting and receiving apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the resonance frequency is adjusted to maximize transmission efficiency at a reference distance, then transmission efficiency is improved at that distance, but transmission efficiency deteriorates when the distance changes
Solution Approach 1:
The patent applies dynamics by making the capacitance values of the capacitors adjustable rather than fixed. The control device dynamically changes the capacitance values in response to distance changes, allowing the resonance frequency to be continuously optimized for different operating conditions. This resolves the contradiction by enabling the system to adapt to varying distances while maintaining high transmission efficiency.
Solution Approach 2:
The patent changes the electrical parameter (capacitance) of the capacitors connected to the self-resonant coils. By adjusting the capacitance values, the resonance frequency of the coils can be tuned to match the prescribed frequency even when the distance between transmitting and receiving apparatus changes. This parameter adjustment directly addresses the contradiction between optimizing for a specific distance and adapting to distance variations.
2Device complexity
If the capacitance is fixed to simplify the system, then device complexity is reduced, but transmission efficiency deteriorates when distance varies
Solution Approach 1:
The control device performs multiple functions: it detects the distance between the transmitting and receiving apparatus, determines the optimal capacitance values based on the detected distance, and adjusts the capacitor settings accordingly. This multi-functional approach consolidates what could be complex separate systems into a single integrated control unit, reducing overall device complexity while maintaining high transmission efficiency across varying distances.
Solution Approach 2:
The system implements feedback by detecting the actual distance between the transmitting and receiving apparatus and using this information to adjust the capacitance values. The control device continuously monitors the operating conditions and modifies the capacitor settings to maintain optimal resonance, creating a closed-loop control system that automatically compensates for distance variations without requiring complex manual adjustments.
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 approach suppresses deterioration in electric power transmission efficiency even when the distance between the apparatus changes, ensuring consistent power transfer by adjusting capacitance to match resonance frequencies and minimize reflected power.
Implementation Method 1
The self-resonant coil receives electric power through electromagnetic resonance with the electric power transmitting apparatus
Implementation Method 2
The capacitor is connected to the self-resonant coil and configured to have a variable capacitance for adjusting a resonance frequency of the self-resonant coil
Data Source
AI summary
In a contactless power feeding system using a resonance method, an electric power receiving apparatus or an electric power transmitting apparatus is connected to a self-resonant coil and includes a capacitor having a variable capacitance. When electromagnetic resonance occurs at a prescribed frequency determined by the electric power transmitting apparatus, the capacitance of the capacitor is adjusted so as to maximize the electric power transmission efficiency during electric power feeding. Accordingly, deterioration in transmission efficiency can be suppressed even when the distance between the secondary self-resonant coil included in the electric power receiving apparatus and the primary self-resonant coil included in the electric power transmitting apparatus changes from a reference distance at the time of design.