Wireless Power Transmitter Frequency Control for Foreign Object Detection
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Solution Overview
Problem
Existing wireless power transfer systems face inefficiencies due to incorrect assumptions about resonant frequencies, leading to reduced power delivery and potential overheating or fires from foreign metallic objects on charging surfaces.
Innovation Solution
A method and system for detecting the actual resonant frequency of a wireless power transmitter and operating at an optimized frequency 1-15% greater than the detected resonant frequency, while also detecting foreign metallic objects by monitoring voltage or current signals to prevent power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the operating frequency is set based on assumed fixed resonant frequency, then the system design is simplified, but power delivery efficiency decreases and control anomalies occur
Solution Approach 1:
The system performs preliminary detection of the actual resonant frequency before power transfer begins. The controller sweeps through a frequency range to identify the peak resonant frequency of the transmitter coil, then sets the operating frequency to be at least 1% greater than this detected value. This preliminary action ensures optimal power delivery efficiency from the start while avoiding control inversion anomalies.
Solution Approach 2:
The system continuously monitors voltage or current signals during operation to detect changes in resonant frequency. When a shift in resonant frequency is detected (indicating foreign object presence or load changes), the controller adjusts the operating frequency accordingly. This feedback mechanism maintains optimal efficiency dynamically while preventing harmful effects from frequency mismatches.
2Productivity
If the operating frequency is lowered to match assumed resonant frequency to increase power, then power delivery is optimized, but control inversion occurs and delivered power decreases
Solution Approach 1:
Before initiating power transfer, the system performs a frequency sweep to detect the actual peak resonant frequency of the transmitter coil. The operating frequency is then set to be at least 1% greater than this detected resonant frequency. This preliminary detection and offset setting prevents control inversion by ensuring the operating frequency remains above the actual resonant frequency even when power delivery is optimized.
Solution Approach 2:
Instead of setting the operating frequency exactly at the detected resonant frequency (which would maximize power but risk control inversion), the system deliberately sets it slightly higher (at least 1% greater). This excessive action—setting frequency above the optimal point—prevents control inversion anomalies while maintaining sufficiently high power delivery efficiency.
3Productivity
If foreign metallic objects are present on charging surface, then power transfer may occur, but overheating and fires can result
Solution Approach 1:
The system continuously monitors voltage or current signals during wireless power transfer to detect the presence of foreign metallic objects. When the monitored signal indicates foreign object presence (such as abnormal current draw or voltage drops), the controller immediately terminates power transfer. This feedback-based detection and response mechanism prevents overheating and fire hazards while allowing normal power transfer when no foreign objects are present.
Solution Approach 2:
The system performs preliminary detection of foreign objects by monitoring voltage or current signals before significant power transfer occurs. When foreign objects are detected, the controller preemptively terminates or prevents power transfer to the affected receiver. This preliminary anti-action stops the harmful heating process before it can lead to overheating or fire, while minimizing disruption to legitimate charging operations.
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 enhances power delivery efficiency by ensuring zero-voltage switching and prevents overheating or fires by accurately adjusting the operating frequency and detecting foreign objects.
Implementation Method 1
Wireless power transfer (WPT) involves the use of time-varying magnetic fields to wirelessly transfer power from a source to a device. Faraday's law of magnetic induction provides that if a time-varying current is applied to one coil (e.g., a transmitter coil) a voltage will be induced in a nearby second coil (e.g., a receiver coil).
Implementation Method 2
The transmitter coil and receiver coil are magnetically coupled, allowing wireless power transfer through the magnetic field generated by the transmitter coil.
Data Source
AI summary
In one embodiment, a method for frequency control in a wireless power transmitter comprises detecting a resonant frequency of the wireless power transmitter, determining an optimized frequency that is at least approximately 1% greater than the detected resonant frequency, and operating the wireless power transmitter at the optimized frequency. In one embodiment, the optimized frequency is approximately 1% to 15% greater than the detected resonant frequency. In one embodiment, the optimized frequency is approximately 5% greater than the detected resonant frequency. In one embodiment, the method further comprises detecting an amount of change in the resonant frequency of the wireless power transmitter, adjusting the optimized operating frequency by the amount of change in the resonant frequency, and operating the wireless power transmitter at the adjusted optimized operating frequency.