Foreign Object Detection in Wireless Power Transfer Using Injection Coils

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Solution Overview

Problem

Wireless power transfer systems face inefficiencies and safety issues due to the presence of foreign objects, such as metal coins or cans, which can intercept and heat up, causing power loss and overheating, and are difficult to detect using existing methods.

Innovation Solution

A device and method that utilize an injection unit to generate a low-power AC signal and an array of coils to create an electromagnetic field, allowing a detection unit to measure changes in the power signal and detect foreign objects within the field, thereby ceasing power transmission to prevent overheating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a foreign object is present in the power transmission path, then the transmitted electric power is received by the foreign object causing heating and power loss, but existing detection methods cannot effectively detect the foreign object

Engineering Contradiction:

Improveforeign object detection capabilityVSAvoiddetection difficulty

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The patent introduces an intermediary detection system with separate detection coils that are distinct from the main power transmission coils. These detection coils generate a detection electromagnetic field specifically for sensing foreign objects without being part of the main power transfer path, allowing indirect detection of foreign objects through their effect on the detection field rather than directly detecting them in the power field.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces physical inspection or contact-based detection methods with electromagnetic field-based detection. By using electromagnetic induction principles, the system detects foreign objects through changes in electrical parameters (current, voltage, impedance) caused by the foreign object's presence in the electromagnetic field, eliminating the need for mechanical detection approaches.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If high power is used for wireless power transfer, then efficient power transmission is achieved, but foreign objects heat up significantly causing safety issues

Engineering Contradiction:

Improvepower transfer efficiencyVSAvoidforeign object heating

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent performs foreign object detection before initiating high-power wireless power transmission. The detection system operates in advance to identify the presence of foreign objects in the transmission path, allowing the system to prevent high-power transmission when foreign objects are detected, thereby avoiding the harmful heating effect while maintaining productivity when the path is clear.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback mechanism where the detection system continuously monitors the electromagnetic field for signs of foreign objects, and this information feeds back to control the power transmission. When foreign objects are detected through changes in electrical parameters, the system automatically adjusts or terminates power transmission to prevent overheating, creating a closed-loop safety system.

Inventive Principle:

Principle #23Feedback

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 without affecting the main power transfer, ensuring system safety and compliance with SAE standards, reducing power loss and improving efficiency by using low-power signals.

Implementation Method 1

an injection unit configured to receive a direct current (DC) power signal and generate a first alternating current (AC) power signal having a first frequency based on the received DC power signal

Methodology Applied

Scientific EffectElectrical signal conversion (DC to AC):

Implementation Method 2

an array of coils operatively coupled to the injection unit and configured to receive the first AC power signal having the first frequency and generate a first electromagnetic field at the first frequency

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 3

detect the foreign object within the first electromagnetic field based on a change in the parameter of at least one of the DC power signal and the first AC power signal across at least one of the array of coils

Methodology Applied

Scientific EffectElectromagnetic field interaction with conductive objects: Electromagnetic Induction

Data Source

PatentUS20210083526A1Device and method for detecting a foreign object in a wireless power transfer system

Publication Date: 2021.03.18 DOLBY INTELLECTUAL PROPERTY LICENSING LLC

AI summary

A device for detecting a foreign object (112) in a WPT system is disclosed. The device includes an injection unit (122) to receive a DC power signal and generate a first AC power signal having a first frequency. Also, the device includes an array of coils (120) to receive the first AC power signal having the first frequency and generate a first electromagnetic field at the first frequency. Further, the device includes a detection unit (124) to measure a parameter of at least one of the DC power signal received by the injection unit (122) and the first AC power signal generated by the injection unit (122), and detect the foreign object (112) within the first electromagnetic field based on a change in the parameter of at least one of the DC power signal and the first AC power signal across at least one of the array of coils (120).