Coil Current Sensing for Wireless Power Foreign Object Detection
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Solution Overview
Problem
Current wireless power transfer systems face limitations in charging multiple devices simultaneously due to foreign object detection (FOD) inefficiencies and heating risks, which affect power transfer efficiency and safety.
Innovation Solution
Implementing a coil current sensing method within a wireless power transmitting device to determine coil current values, compute transmitter power loss, and detect foreign objects by monitoring changes in power loss that meet specific threshold conditions, enhancing precision and safety during high-power charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple wireless chargers are used to charge multiple devices simultaneously, then charging capacity is improved, but system cost and complexity increase
Solution Approach 1:
The patent implements a multi-coil transmitter system where a single wireless power transmitter can simultaneously charge multiple devices through multiple transmitter coils (first transmitter coil and second transmitter coil). This allows one device to perform the function of multiple chargers, improving productivity while reducing system complexity and cost.
Solution Approach 2:
The transmitter is divided into multiple independent transmitter coils, each capable of independently charging a device. The system includes a first transmitter coil and a second transmitter coil that can operate simultaneously or independently, allowing the system to scale charging capacity without proportionally increasing overall system complexity.
2Reliability
If foreign object detection capacity is increased to improve safety, then detection accuracy is improved, but circuit area and IC chip complexity increase
Solution Approach 1:
The system uses the existing transmitter coils and circuitry to perform foreign object detection without requiring separate dedicated detection hardware. The same first and second transmitter coils used for power transfer are also utilized for FOD by monitoring changes in their operating characteristics, allowing the system to self-diagnose foreign objects using its own components.
Solution Approach 2:
The transmitter coils serve dual purposes: power transfer and foreign object detection. By monitoring the current and impedance changes in the transmitter coils during operation, the system can detect foreign objects using the same hardware infrastructure, avoiding the need for additional dedicated detection circuits.
3Productivity
If power transfer efficiency is increased for high-power charging, then charging speed is improved, but heating risks and foreign object detection challenges increase
Solution Approach 1:
The system continuously monitors the operating parameters of the transmitter coils during power transfer and uses this feedback to detect foreign objects and adjust operation. By monitoring changes in coil current and impedance, the system can identify foreign objects in real-time and modify power transfer parameters to prevent excessive heating, enabling safe high-power charging.
Solution Approach 2:
The system dynamically adjusts its operation based on real-time conditions. The controller can modify the power transfer parameters, coil selection, and operating frequency based on detected foreign objects or heating conditions, allowing the system to optimize charging speed while maintaining safety through continuous adaptation.
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 accurate detection of foreign objects, improving the efficiency and safety of wireless power transfer, enabling simultaneous charging of multiple devices with increased active charging area and reduced heating risks.
Implementation Method 1
a transmitter device, driven by electric power from a power source, generates a time-varying electromagnetic or magnetic field, which transmits power across space to a receiver device
Implementation Method 2
determining, via a coil current sensing circuit at the wireless power transmitting device, a coil current value corresponding to a first coil current that passes through a first transmitter coil
Data Source
AI summary
Embodiments described herein provide foreign object detection based on coil current sensing. The transmitter power loss is computed directly based on the coil current, in conjunction with, or in place of the conventional computation based on transmitter input current. The enhanced precision of the computer power loss can be used to more accurately detect a foreign object near the transmitter coil during a wireless power transfer.