Foreign Object Detection in Inductive Power Transfer
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Solution Overview
Problem
Inductive power transfer systems face challenges in efficiently detecting foreign objects, particularly those located between the transmitter and receiver, which can cause damage and unwanted current induction, and existing solutions often require additional costly detection circuitry and are not effective in non-resonant power transfer scenarios.
Innovation Solution
A method and device that utilize control circuitry to estimate real and reactive power in the transmitter coil, determining the presence of foreign objects by analyzing the stabilized current and voltage characteristics, without the need for additional detection circuitry, and can operate in both resonant and non-resonant power transfer modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional detection circuitry is used for foreign object detection, then detection capability is improved, but system cost and complexity increase
Solution Approach 1:
The transmitter coil serves dual functions: power transfer and foreign object detection. By monitoring the electrical characteristics (impedance, current, voltage) of the transmitter coil during normal operation, the system can detect foreign objects without requiring separate detection circuitry. The control circuitry analyzes changes in real and reactive power to identify the presence of foreign objects.
Solution Approach 2:
The system uses its own operational parameters (current, voltage, impedance of the transmitter coil) to perform self-diagnosis for foreign object detection. The control circuitry continuously monitors the electrical characteristics during power transfer and automatically detects foreign objects by analyzing deviations from normal operating conditions, eliminating the need for external detection systems.
2Power
If resonant circuit is used for power transfer, then power throughput is improved, but foreign object detection effectiveness is reduced in non-resonant scenarios
Solution Approach 1:
The detection method monitors electrical parameters (impedance, current, voltage, real power, reactive power) that change in response to foreign object presence regardless of whether the system is operating in resonant or non-resonant mode. By tracking these parameter variations during normal power transfer operation, the system achieves foreign object detection capability that is effective across different power transfer modes without requiring mode-specific detection circuits.
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
Effectively detects foreign objects, preventing damage to the transmitter and receiver, and reduces system cost by eliminating the need for additional detection circuitry, while being applicable to both resonant and non-resonant power transfer systems.
Implementation Method 1
a primary side or transmitter generates a time-varying magnetic field with a transmitting coil or coils. This magnetic field induces an alternating current in a suitable receiving coil or coils
Implementation Method 2
the transmitter coil(s) or the receiver coil(s) may be connected to capacitors to create a resonant circuit, which can increase power throughput or efficiency at the corresponding resonant frequency
Data Source
AI summary
A method for determining the presence of a foreign object in an inductive power transfer field in which control circuitry of an inductive power system performs the steps of: providing power to a direct current to alternating current converter; providing power from the converter to a transmitter coil in the inductive power transfer field; waiting for the current in the transmitter coil to stabilize; estimating the reactive power in the transmitter coil; estimating the real power in the transmitter coil; and using the estimated reactive power and estimated real power to determine whether a foreign object is present.