Wireless Power Transmitter Impedance Tuning for Low-Coupling Charging
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Solution Overview
Problem
Existing wireless charging systems face inefficiencies due to low coupling between transmitting and receiving coils, especially at increased distances or with intervening materials, leading to reduced power transfer efficiency.
Innovation Solution
A wireless power transmitter dynamically adjusts impedance by controlling a slave transmitter resonant tank to optimize the phase and amplitude of currents, while the receiver tunes its resonance frequency using a tunable capacitor and boost converter to enhance power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the distance between transmitting and receiving coils is increased, then spatial freedom is improved, but coupling efficiency deteriorates
Solution Approach 1:
The patent implements dynamic impedance adjustment by controlling the slave transmitter driver to modify the phase angle between master and slave currents. This dynamic adaptation allows the system to maintain optimal coupling efficiency across varying distances, resolving the contradiction between spatial freedom and power transfer efficiency.
Solution Approach 2:
The system changes operating parameters (phase angle, impedance) based on coupling conditions. The controller adjusts the phase angle between master and slave transmitter currents to optimize power transfer at different distances, enabling the system to maintain efficiency while providing spatial freedom.
2Reliability
If intervening materials are placed between coils, then hermetic sealing is improved, but coupling efficiency deteriorates
Solution Approach 1:
The system employs feedback control where the controller monitors the coupling conditions and dynamically adjusts the phase angle and impedance of the slave transmitter. This feedback mechanism compensates for the detrimental effects of intervening materials, maintaining power transfer efficiency while allowing hermetic sealing.
Solution Approach 2:
The patent changes operating parameters (phase angle, impedance) in response to the presence of intervening materials. By dynamically adjusting these parameters, the system compensates for the reduced coupling efficiency caused by materials between the coils, thus maintaining reliable power transfer with hermetic sealing.
3Loss of energy
If resonant frequency is tuned to match transmitter frequency, then power transfer efficiency is improved, but device complexity increases
Solution Approach 1:
The receiver device performs self-tuning by automatically adjusting its resonant frequency to match the transmitter frequency. The controller on the receiver side autonomously controls the tunable capacitor to achieve resonance matching, eliminating the need for complex external tuning equipment and simplifying the overall system.
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 improves wireless power transmission over varying distances and through materials, maintaining efficient power transfer by dynamically adjusting impedance and resonance frequency, allowing for reliable charging across different scenarios.
Implementation Method 1
The Qi standard uses inductive charging operating between 80 kHz and 300 kHz to wirelessly transmit power from a transmitter to a receiver
Implementation Method 2
The Qi standard uses inductive charging operating between 80 kHz and 300 kHz to wirelessly transmit power from a transmitter to a receiver
Implementation Method 3
the controller is configured to adjust the tunable capacitor to move a resonance frequency towards an operating frequency of a transmitter current
Implementation Method 4
Standards promoted by the AirFuel alliance use resonant wireless charging operating at 6.78 MHz to wirelessly transmit power from a transmitter to a receiver
Data Source
AI summary
In an embodiment, a wireless power transmitter includes: a master transmitter resonant tank configured to wirelessly transmit power to a receiver resonant tank; a master transmitter driver configured to drive the master transmitter resonant tank; a slave transmitter resonant tank; a slave transmitter driver configured to drive the slave transmitter resonant tank; and a controller configured to adjust an impedance seen by the master transmitter resonant tank by controlling the slave transmitter driver, where controlling the slave transmitter driver includes adjusting a phase angle between a slave transmitter current flowing through the slave transmitter resonant tank and a master transmitter current flowing through the master transmitter resonant tank or adjusting a slave supply voltage of the slave transmitter driver.