Wireless Power Coil Control for Thermal Foreign Object Detection
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Solution Overview
Problem
Existing wireless power transmission systems face challenges in detecting and removing metal foreign objects, such as empty cans or coins, which can cause safety concerns and disrupt normal charging operations. Current methods require the vehicle to be moved to remove the foreign object, and cameras may struggle to detect objects covered in dirt or at night.
Innovation Solution
A method that includes a power transmitting device with a power transmitting coil, a thermal sensor to detect temperature changes, and a power transmission control circuit. The system outputs initial power to detect metal foreign objects before the vehicle overlaps the coil, measures the temperature, and reduces or stops power output if the temperature exceeds a threshold, allowing for safe removal of the foreign object.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a camera is used to detect metal foreign objects, then detection capability is improved, but the system cannot detect objects covered in dirt or at night, and the vehicle must be moved to remove detected objects
Solution Approach 1:
The patent replaces the camera-based optical detection system with a thermal sensor-based thermal detection system. The thermal sensor detects temperature changes caused by metal foreign objects when exposed to the magnetic field of the power transmitting coil, enabling detection without requiring visual line of sight or good lighting conditions. This substitution resolves the limitation of camera-based detection for covered or nighttime scenarios.
Solution Approach 2:
The patent implements preliminary detection of metal foreign objects before the vehicle overlaps with the power transmitting coil. The control unit detects the presence of metal foreign objects in advance by monitoring temperature changes during a preliminary power transmission phase, allowing the vehicle to be alerted and the objects to be removed before they cause safety issues or disrupt normal charging operations.
2Productivity
If power is transmitted at high level continuously, then charging efficiency is improved, but metal foreign objects can be heated causing safety concerns
Solution Approach 1:
The patent implements periodic detection and control cycles during the power transmission process. The control unit alternates between transmitting power at high levels for efficient charging and monitoring temperature changes to detect metal foreign objects. When a metal foreign object is detected, the power transmission is temporarily reduced or stopped, then resumed at high power once the object is removed, maintaining both safety and charging efficiency.
Solution Approach 2:
The patent employs a feedback mechanism where the control unit continuously monitors temperature changes in the power transmission area and adjusts the power transmission level accordingly. When temperature changes indicate the presence of a metal foreign object, the control unit reduces or stops power transmission to prevent heating. When temperature stabilizes within safe ranges, the control unit resumes high-level power transmission for efficient charging.
3Measurement precision
If thermal sensor is used to detect metal foreign objects, then detection accuracy is improved, but the system complexity increases
Solution Approach 1:
The patent designs the thermal sensor to serve multiple functions: detecting metal foreign objects, monitoring temperature during power transmission, and providing safety shutdown signals. The control unit integrates the thermal sensor data with the power transmission control, eliminating the need for separate detection and control systems. This multi-functional approach improves detection accuracy while minimizing the increase in system complexity.
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 solution enables the detection and safe removal of metal foreign objects before they cause heating issues, ensuring normal and prompt non-contact power transmission can commence.
Implementation Method 1
A wireless power transmission system used for a mobile object such as a vehicle electromagnetically couples a power transmitting coil included in a power transmitting device and a power receiving coil included in a power receiving device with each other and transmits power from the power transmitting coil to the power receiving coil
Implementation Method 2
a thermal sensor that detects a temperature around the power transmitting coil
Implementation Method 3
If there is a metal foreign object such as an empty can or a coin between the power transmitting coil and the power receiving coil, the surface temperature of the metal foreign object increases due to a magnetic field generated by the power transmitting coil during power transmission
Data Source
AI summary
A power transmitting device includes a power transmitting coil for providing output power to a power receiving coil, a thermal sensor that detects a temperature around the power transmitting coil, and a power transmission control circuit that controls the power transmitting device. The power transmission control circuit performs operations including causing the power transmitting coil to provide first output power, causing the power transmitting coil to provide second output power to the power receiving coil for charging a battery connected to the power receiving coil, causing, if the detected temperature is equal to or higher than a threshold due to a presence of a metal foreign object, the power transmitting coil to reduce a level of the output power or stop the output power, and outputting a first signal indicating whether the metal foreign object is detected.