Wireless Power Coil Bandwidth Comparison for Foreign Object Detection
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Solution Overview
Problem
Existing wireless power transfer systems, particularly those with multi-coil transmitters, struggle to accurately detect foreign objects due to changes in transmitter characteristics and the presence of magnets, leading to incorrect power calibration and wastage.
Innovation Solution
The method involves determining the transmitter frequency bandwidth and comparing it with the transmitter-receiver resonant frequency bandwidth to detect foreign objects by analyzing the changes in frequency bandwidth caused by the presence of a foreign object.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If reference Q value method is used for foreign object detection, then detection can be performed with initial transmitter designs, but detection accuracy deteriorates with newer transmitter topologies having low Q or embedded magnets
Solution Approach 1:
The patent changes the detection parameter from Q value to frequency bandwidth. By measuring the frequency bandwidth of the transmitter coil and comparing it to expected values, the system can accurately detect foreign objects regardless of transmitter topology variations, low Q values, or embedded magnets that make Q value detection unreliable
2Ease of operation
If analog ping or digital ping methods are used, then receiver detection can be performed, but foreign object differentiation fails particularly when transmitters have magnets
Solution Approach 1:
The patent introduces frequency bandwidth measurement as an intermediary detection method. Instead of directly detecting foreign objects through ping methods that fail with magnets, the system measures the frequency bandwidth of the transmitter coil, which changes in a predictable way when foreign objects are present, enabling accurate differentiation between receivers and foreign objects
3Reliability
If Q value measurement is used, then foreign object detection can be attempted, but sensitivity is significantly reduced with low Q transmitters or transmitters with magnets
Solution Approach 1:
The patent switches from measuring Q value to measuring frequency bandwidth. Frequency bandwidth provides consistent detection sensitivity across all transmitter types including low Q transmitters and those with embedded magnets, eliminating the sensitivity problems inherent in Q value-based detection
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 accurately detects foreign objects without relying on reference Q values from the receiver, ensuring precise power transfer and preventing heating and power wastage.
Implementation Method 1
a transmitter of a transmitting device may generate an electromagnetic field, and a receiver of a receiving device may extract power from the electromagnetic field
Implementation Method 2
a transmitter of a transmitting device may generate an electromagnetic field, and a receiver of a receiving device may extract power from the electromagnetic field
Data Source
AI summary
A wireless power transmitter and methods to: determine a transmitter frequency bandwidth of the wireless power transmitter when no wireless power receiver is inductively coupled with the wireless power transmitter; determine a transmitter-receiver frequency bandwidth when a wireless power receiver is inductively coupled with the wireless power transmitter; compare the transmitter-receiver frequency bandwidth and the transmitter frequency bandwidth; and detect a foreign object near the transmit coil based on the comparison of the transmitter-receiver frequency bandwidth and the transmitter frequency bandwidth.