Inductive Power Transmitter Foreign Object Detection via Waveform Correlation
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Solution Overview
Problem
Existing inductive power transfer systems face challenges in accurately distinguishing between intended receiver devices and foreign objects, leading to inefficient power transfer and potential overheating of foreign objects due to the lack of reliable object detection methods.
Innovation Solution
An inductive power transmitter equipped with an object detection system that correlates voltage or current waveforms with a reference waveform to identify potential receiver objects, enabling selective activation and deactivation of the power transmitting coil based on successful communication attempts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power loss method is used to detect foreign objects, then power transfer safety is improved, but detection accuracy deteriorates because it only indicates abnormal behavior without actual foreign object detection
Solution Approach 1:
A detection coil is introduced as an intermediary element separate from the power transfer coil. This detection coil specifically senses foreign objects through electromagnetic induction without being involved in power transfer, thereby improving detection accuracy without compromising power transfer safety
Solution Approach 2:
The system is segmented into two independent functional components: a power transfer coil for energy transmission and a detection coil for foreign object sensing. This segmentation allows each component to optimize its specific function, with the detection coil providing accurate foreign object detection independent of power transfer operations
2Measurement precision
If separate detection coils are used for foreign object detection, then detection capability is improved, but device complexity increases due to additional components and calibration requirements
Solution Approach 1:
The detection coil is designed with multi-functionality, serving both as a foreign object detection sensor and as part of the overall electromagnetic sensing system. By integrating detection functionality into the existing coil structure rather than adding completely separate complex detection systems, the patent reduces overall device complexity while maintaining enhanced detection capability
Solution Approach 2:
The detection coil uses a simplified version of the power transfer coil structure, copying only the essential electromagnetic sensing properties without the full power transfer capability. This allows foreign object detection using a simpler, lower-cost coil design that doesn't require full calibration of power transfer parameters
3Reliability
If continuous monitoring is implemented to detect objects on charging pad, then safety is improved, but power consumption increases
Solution Approach 1:
Instead of continuous monitoring, the system implements periodic detection at key moments: when an object is placed on the charging pad and before power transfer begins. This periodic action maintains safety by detecting foreign objects at critical points while significantly reducing power consumption compared to continuous monitoring
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 effectively prevents power transfer to foreign objects, reducing energy wastage and preventing overheating, while ensuring efficient charging of intended devices by accurately differentiating between receiver devices and foreign objects.
Implementation Method 1
a power transmitter generates a time-varying magnetic field from a transmitting coil or coils
Implementation Method 2
This magnetic field induces an alternating current in a suitable receiving coil in a power receiver
Implementation Method 3
detect a potential receiver object based on a magnet associated with the receiver object by correlating a shape of a voltage versus time waveform or a current versus time waveform with a reference waveform shape, wherein the voltage versus time or current versus time waveform is magnetically induced by the magnet associated with the potential receiver object
Implementation Method 4
For example if a parasitic metal is close to the active IPT area it could heat up during power transfer due to eddy currents that result from the oscillating magnetic field
Data Source
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Figure 4
AI summary
An inductive power transmitter comprising: a power transmitting coil configured to generate an inductive power transfer (IPT) field; and an object detection system configured to detect objects in or adjacent a space occupied by the IPT field when generated; wherein the object detection system is configured to: detect a potential receiver object by correlating a shape of a voltage versus time waveform or a current versus time waveform with a reference waveform shape, wherein the voltage versus time or current versus time waveform is magnetically induced by the potential receiver object; energize the power transmitting coil and attempt to communicate with the potential receiver object in response to detecting the potential receiver object; and de-energize the power transmitting coil in response to a failure in the attempt to communicate with the potential receiver object