Non-contact Power Reception Device Impedance Switching
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Solution Overview
Problem
Existing wireless power transfer systems using the resonance method do not have a reliable mechanism to stop power reception when it is not required, such as when a vehicle's power storage device is fully charged.
Innovation Solution
A non-contact power reception device with a secondary self-resonant coil that can be switched between a power reception mode and a power non-reception mode by modifying its impedance through the use of relays and capacitance modifiers, ensuring weaker magnetic coupling with the primary self-resonant coil during non-reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the resonance method is used for wireless power transfer, then power can be transferred over a relatively long distance, but there is no reliable mechanism to stop power reception when it is not required
Solution Approach 1:
The patent applies the dynamics principle by making the secondary self-resonant coil's impedance switchable between different states. The coil can dynamically transition between a first impedance state (enabling resonance and power reception) and a second impedance state (disabling resonance and stopping power reception). This dynamic impedance control allows reliable start and stop of power reception while maintaining the ability to transfer power over long distances through resonance.
Solution Approach 2:
The patent implements parameter changes by modifying the impedance parameter of the secondary self-resonant coil. By changing the impedance from a first value (tuned for resonance with the primary coil) to a second value (detuned from resonance), the system can control power reception. This parameter change approach enables the coil to selectively enter or exit resonant coupling with the primary coil, providing reliable power reception control.
2Productivity
If the secondary self-resonant coil is continuously magnetically coupled with the primary self-resonant coil, then power reception is maintained, but unnecessary energy transfer occurs when power storage device is full
Solution Approach 1:
The patent applies periodic action by enabling the secondary self-resonant coil to alternately switch between resonant and non-resonant states based on power storage needs. The control system periodically assesses the power storage device's charge level and accordingly switches the coil's impedance between first and second states. This periodic switching ensures power reception occurs only when needed, preventing continuous unnecessary energy transfer while maintaining productivity when the storage device requires charging.
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 reliable stopping of power reception when it is not needed, preventing unnecessary energy transfer and maintaining efficient power management in vehicles.
Implementation Method 1
The secondary self-resonant coil is configured so as to be switchable between a first state and a second state. The first state is selected in a power reception mode in which the secondary self-resonant coil is magnetically coupled with the primary self-resonant coil through resonance of a magnetic field.
Implementation Method 2
The secondary self-resonant coil is magnetically coupled with the primary self-resonant coil through resonance of a magnetic field
Data Source
AI summary
A non-contact power reception device includes a load such as a power storage device identified as a subject of power feeding, and a secondary self-resonant coil receiving electric power to be supplied to said load from an external primary self-resonant coil. The secondary self-resonant coil is configured so as to be switchable between a first state and a second state. The first state is selected in a power reception mode in which the secondary self-resonant coil is magnetically coupled with the primary self-resonant coil through resonance of a magnetic field. The second state is selected in a power non-reception mode in which the magnetic coupling of the secondary self-resonant coil with the primary self-resonant coil through resonance is weaker than in the first state.