Foreign Object Detection in Wireless Power Transfer Systems
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Solution Overview
Problem
Existing non-contact power transmission systems face challenges in accurately detecting foreign objects due to difficulties in distinguishing normal loads from pseudo-loads caused by foreign objects, especially when eddy current losses occur, which affects the reliability of power transmission.
Innovation Solution
A power transmission control device that includes a driver control circuit, a load state detection circuit, and a control circuit, which performs a foreign object detection process based on load state detection information after receiving ID authentication information from the power receiving device, allowing for accurate detection of foreign objects before starting normal power transmission by creating a constant load condition and using distinct frequencies for foreign object detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a primary-side detection circuit detects eddy current loss to identify foreign objects, then foreign object detection capability is provided, but the detection circuit cannot determine whether the power-receiving-side load is a normal load or a pseudo-load due to a foreign object
Solution Approach 1:
The system performs foreign object detection before starting normal power transmission by detecting load state during a preliminary period after ID authentication. This preliminary detection allows the system to identify foreign objects before they can cause harmful effects, while the load is in a known initial state, enabling accurate discrimination between normal and pseudo-loads
Solution Approach 2:
The control circuit continuously monitors load state detection information and uses this feedback to determine whether to start normal power transmission. The feedback mechanism allows the system to adjust its operation based on detected conditions, ensuring safe power transmission only when no foreign objects are present
2Productivity
If power transmission starts immediately after ID authentication, then power transmission efficiency is improved, but foreign objects may cause eddy current losses and safety issues
Solution Approach 1:
The system performs foreign object detection during a preliminary period after ID authentication but before starting normal power transmission. This preliminary action ensures that any foreign objects are detected before they can cause harmful eddy current losses, while minimizing the delay to power transmission by performing detection only during the authentication sequence
Solution Approach 2:
The system takes preliminary anti-action by detecting and identifying foreign objects before they can cause harmful effects. The control circuit prevents normal power transmission from starting if foreign objects are detected, thereby preventing eddy current losses and safety issues before they can occur
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
The solution improves foreign object detection accuracy by performing the detection process before normal power transmission, ensuring that only authorized loads receive power and enhancing the reliability of non-contact power transmission systems.
Implementation Method 1
non-contact power transmission system transmitting power from the power transmitting device to the power receiving device by electromagnetically coupling a primary coil and a secondary coil
Implementation Method 2
a load state detection circuit that detects a power-receiving-side load state
Data Source
AI summary
A power transmission control device provided in a power transmitting device of a non-contact power transmission system includes a driver control circuit that controls a power transmitting driver that drives a primary coil, a load state detection circuit that detects a power-receiving-side load state, and a control circuit that controls the driver control circuit. The control circuit performs a foreign object detection process based on load state detection information from the load state detection circuit after receiving ID authentication information from a power receiving device, and starts normal power transmission to the power receiving device after performing the foreign object detection process.