Coupled-Coil Power Control for Inductive Transfer
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Solution Overview
Problem
Inductive power transfer systems face challenges in regulating power to loads efficiently, particularly due to the need for large DC inductors and high-loss switches in receiver-side power control, and non-resonant receiving coils that may not comply with industry standards.
Innovation Solution
An inductive power transfer device with a resonant circuit, a magnetically-coupled coupling coil, and a variable impedance controlled by a controller to regulate power, adjust the resonant frequency, and modulate the impedance, allowing for efficient power control and compliance with industry standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If receiver-side power control uses regulating stages, then power can be controlled, but large DC inductors are required increasing receiver volume
Solution Approach 1:
The patent removes the DC inductor from the receiver circuitry by implementing power control through transmitter-side adjustment and resonant frequency tuning. The receiver simply rectifies and outputs power without needing regulating stages or DC inductors, thus eliminating the volume constraint while maintaining power control capability.
Solution Approach 2:
The patent introduces a coupled resonant pickup coil as an intermediary element that enables power control without requiring DC inductors in the receiver. By adjusting the resonant frequency of this coupled coil, power transfer can be regulated while keeping the receiver compact and free of large magnetic components.
2Ease of operation
If switches are used to adjust coil tuning, then power control is achieved, but high losses occur due to peak currents and voltages
Solution Approach 1:
The patent uses periodic switching of capacitors in the resonant circuit to adjust tuning and control power. By switching capacitors at appropriate moments in the AC cycle and using resonant frequency adjustment, the system achieves power control with minimal switching losses compared to continuous switching of main power switches.
Solution Approach 2:
The patent controls power by changing the resonant frequency parameter of the transmitting coil and coupled resonant pickup coil, rather than using high-power switches. This parameter-based control (frequency and impedance adjustment) eliminates the need for high-voltage, high-current switches that cause significant energy losses.
3Device complexity
If non-resonant receiving coils are used, then power control is simplified, but compliance with industry standards is lost
Solution Approach 1:
The patent implements a resonant receiving coil system that can comply with industry standards while maintaining simplified power control. The system uses a coupled resonant pickup coil that serves multiple functions: enabling power control through frequency adjustment and ensuring compatibility with wireless power transfer standards, thus achieving both simplicity and compliance.
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 enables precise power regulation, reduces losses, and ensures compliance with industry standards by using a magnetically-coupled coupling coil and variable impedance to control power transfer, improving efficiency and miniaturization in inductive power transfer systems.
Implementation Method 1
a primary side (i.e., an inductive power transmitter) will include a transmitting coil or coils configured to generate an alternating magnetic field. This magnetic field induces an alternating current in the receiving coil or coils of a secondary side
Implementation Method 2
a coupling coil, magnetically-coupled to the power transfer coil
Implementation Method 3
the transmitting coil(s) or the receiving coil(s) may be suitably connected with capacitors to create a resonant circuit. This can increase power throughput and efficiency at the corresponding resonant frequency
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
An inductive power transfer device including: a resonant circuit, having a power transfer coil and a power transfer capacitor; a coupling coil, magnetically-coupled to the power transfer coil; a variable impedance; and a controller configured to determine the impedance value of the variable impedance based on predetermined criteria including: substantially regulating power provided to a load; tuning the resonant circuit resonant frequency substantially to a predetermined frequency; adjusting a frequency of a magnetic field associated with the power transfer coil; and/or adjusting an impedance reflected by the power transfer coil to a corresponding coupled power transfer coil.