Wireless Power Coil Loss Modeling for Foreign Object Detection
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Solution Overview
Problem
The existing methods for foreign object detection in wireless power transfer systems, particularly those using the Qi 2.0 Magnetic Power Profile, are complex and require expensive test setups, making them inaccessible to many system designers, and do not accurately account for additional losses introduced by magnets in newer transmitters and receivers.
Innovation Solution
A method using commonly available test equipment to measure inductance and resistance of transmitter and receiver coils in standalone and mated conditions, creating a simulation model to detect power loss accurately, which can be used to identify the presence of foreign objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If expensive RF based test setup with LCR meter and sinewave generator is used to measure FM loss, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent creates an electrical equivalent circuit model that copies the electrical behavior of the complex magnetic field system. Instead of measuring the actual complex electromagnetic interactions with expensive RF equipment, the invention uses a simplified electrical circuit model with equivalent impedance parameters that reproduces the same measurement results, making the test setup accessible to ordinary system designers
Solution Approach 2:
The patent replaces the complex electromagnetic measurement system (RF based test setup with LCR meter and sinewave generator) with an electrical circuit measurement approach. By substituting the mechanical/electromagnetic measurement apparatus with electrical impedance measurements using an equivalent circuit model, the invention simplifies the test equipment requirements while maintaining measurement accuracy
2Stability of the object's composition
If magnets are added to transmitter and receiver for firm coupling, then coupling stability is improved, but additional friendly metal losses are introduced that complicate FO detection
Solution Approach 1:
The patent extracts the magnet-related losses from the overall power loss measurement by creating a separate electrical equivalent circuit model for the magnets. This allows the system to account for and subtract the friendly metal losses caused by magnets, isolating the foreign object detection signal from the background magnet losses
Solution Approach 2:
The patent changes the measurement approach by using electrical impedance parameters (resistance and reactance) to characterize the magnetic components. By measuring the equivalent impedance of the magnet assembly and using this to calculate expected power losses, the system can distinguish between normal magnet losses and additional losses caused by foreign objects
3Difficulty of detecting and measuring
If power loss method is used for FO detection, then detection capability is improved, but accuracy deteriorates due to unaccounted magnet losses
Solution Approach 1:
The patent implements feedback by continuously monitoring the electrical impedance parameters of the magnet assembly and using this information to dynamically adjust the foreign object detection threshold. The system measures the baseline impedance without foreign objects, then uses this feedback to distinguish normal variations from actual foreign object presence, improving detection accuracy
Solution Approach 2:
The patent performs preliminary characterization of the magnet assembly by measuring its electrical equivalent circuit parameters before foreign object detection begins. This preliminary action establishes a baseline model of normal magnet losses, which is then used to interpret subsequent power loss measurements and distinguish them from foreign object effects
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
Enables accurate foreign object detection using affordable test equipment, reducing the complexity and cost of the detection process while maintaining precision, thereby preventing potential overheating and catastrophic failures.
Implementation Method 1
The transmitter contains at least one coil with which the receiver coil is coupled in a typical wireless system
Implementation Method 2
measuring inductance and resistance of the transmitter coil in standalone conditions using a meter circuit when a plurality of currents are applied to the transmitter coil
Implementation Method 3
The newer class if transmitters and receivers contain magnets which hold them together
Implementation Method 4
The Qi power loss method uses a difference between the power transmitted by the transmitter and the power received by the receiver to compute the power loss
Data Source
AI summary
A foreign object may be detected by measuring inductance and resistance of a transmitter coil using a meter circuit when a plurality of currents are applied to the transmitter coil when the transmitter coil is in standalone conditions and when a receiver coil is mated to the transmitter coil without a foreign object present. A simulation model is generated based on the measured inductance and resistance of the transmitter coil and receiver coil and comprising a characteristic curve as a function of the plurality of currents applied to the transmitter coil. With the receiver coil mated to the transmitter coil, a foreign object may be detected by measuring a power loss from the transmitter coil to the receiver coil based on the simulation model.