Wireless Power Coil Shielding for Accurate Foreign Object Detection
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Solution Overview
Problem
Current wireless power transfer systems face challenges in accurately detecting foreign objects due to uncertainties in internal metal properties of devices and varying power levels, leading to suboptimal performance and potential heating issues.
Innovation Solution
Incorporating a magnetic shielding element with a saturation point that operates in a saturated mode during power transfer and a non-saturated mode during foreign object detection, reducing the impact of power transfer coils on detection and enhancing the electromagnetic environment for improved foreign object detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a strong electromagnetic field is generated for high power wireless power transfer, then power transfer efficiency is improved, but foreign object detection accuracy deteriorates due to saturation of magnetic shielding elements
Solution Approach 1:
The system alternates between power transfer mode and detection mode in periodic time intervals. During power transfer mode, the full electromagnetic field is applied for efficient power transfer. During detection mode, the field is reduced below saturation levels to enable accurate foreign object detection. This periodic switching resolves the contradiction by allowing both high power transfer efficiency and accurate detection at different times.
Solution Approach 2:
The magnetic shielding element's operating state is dynamically changed between saturated and non-saturated modes based on the operational phase. The system adapts the field strength dynamically - maintaining high field strength during power transfer for efficiency, and reducing field strength during detection for accuracy. This dynamic adaptation allows the system to optimize both contradictory requirements.
2Measurement precision
If the magnetic field strength is reduced for foreign object detection, then detection accuracy is improved, but power transfer efficiency deteriorates
Solution Approach 1:
The system uses periodic time intervals to switch between detection mode (low field strength for accuracy) and power transfer mode (high field strength for efficiency). This ensures that detection accuracy is maintained when needed without permanently compromising power transfer efficiency.
Solution Approach 2:
The system maintains continuous operation by rapidly alternating between detection and power transfer phases. The useful actions of both detection and power transfer are maintained continuously over time, with the system switching between them fast enough that both functions remain effective.
3Adaptability or versatility
If internal metal properties of devices are considered in detection algorithms, then device compatibility is improved, but detection complexity increases due to uncertainties in metal properties
Solution Approach 1:
The system extracts and compensates for the known effects of internal metal properties (such as the receiver coil and friendly metals) from the detection signal. By removing these predictable interference components, the detection algorithm becomes simpler as it only needs to detect foreign objects without dealing with the complexity of varying internal metal properties.
Solution Approach 2:
The system uses the magnetic shielding element as an intermediary that creates a controlled magnetic environment. This intermediary structure provides a known reference frame that simplifies detection algorithms by reducing the impact of uncertainties in internal metal properties of different devices.
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 allows for more accurate foreign object detection with reduced sensitivity to device variations and power levels, improving performance and adaptability while maintaining efficient power transfer.
Implementation Method 1
the magnetic shielding element comprises a magnetic shield material having a saturation point such that it operates in a saturated mode during power transfer intervals
Implementation Method 2
power is inductively transferred from a transmitter coil in a power transmitter device to a receiver coil in the individual devices
Implementation Method 3
operates in a non-saturated mode during foreign object detection time intervals, the saturation point being above a magnetic field strength generated by the power transfer signal during the power transfer time intervals and below a magnetic field strength generated during the foreign object detection time intervals
Data Source
AI summary
A wireless power transmitter (101) or power receiver (105) comprises a power transfer coil (103, 107) for receiving or generating a power transfer signal and a controller (201, 301) for controlling the device to perform power transfer during a power transfer phase. The power transfer phase comprises power transfer intervals where power is transferred and foreign object detection time intervals during which a power level of the power transfer signal is reduced. A magnetic shielding element (503, 505) is positioned between the power transfer coil (103, 107) and a power transfer coil of a complementary device. The magnetic shielding element (503, 505) comprises a magnetic shield material having a saturation point such that it operates in a saturated and non-saturated mode during respectively power transfer intervals and foreign object detection time intervals. The saturation point is above a magnetic field strength generated by the power transfer signal during the power transfer time intervals and below that generated during the foreign object detection time intervals.