Wireless Power Transfer Foreign Object Detection

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Solution Overview

Problem

Existing wireless power transfer systems face challenges in detecting foreign objects within the electromagnetic fields, which can lead to inefficient power transfer and potential heating issues.

Innovation Solution

A method is implemented by the control circuitry of a wireless power transmitter to detect foreign objects by comparing measured power loss with a predicted power loss, calculated using coefficients derived from baseline wireless power transmission data and rectifier voltage and current measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If wireless power transfer is performed at higher power levels to enable faster charging, then charging speed is improved, but the risk of foreign object heating and power transfer inefficiency increases

Engineering Contradiction:

Improvecharging speedVSAvoidforeign object heating

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary characterization of the power transfer path by measuring power loss at multiple operating points before actual power transfer. These measurements establish baseline coefficients that are stored and used during operation to predict and detect foreign objects in real-time, enabling preventive detection before heating occurs

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors actual power transfer and compares it against predicted power loss calculated from stored coefficients. When deviations exceed thresholds, the system alerts users to potential foreign objects, providing real-time feedback that enables corrective action to prevent harmful heating while maintaining high power transfer capability

Inventive Principle:

Principle #23Feedback

2Difficulty of detecting and measuring

If foreign object detection is implemented using traditional electromagnetic field sensing, then detection capability is provided, but device complexity and cost increase

Engineering Contradiction:

Improveforeign object detection capabilityVSAvoiddetection system complexity

Core Design Contradiction:

Difficulty of detecting and measuringVSDevice complexity

Solution Approach 1:

The system uses the existing power transfer infrastructure and measurements to detect foreign objects. By analyzing power loss characteristics during normal power transfer operations, the system extracts foreign object detection information without requiring separate detection hardware, sensors, or additional electromagnetic field sensing systems

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The power loss measurement system serves dual purposes: characterizing the power transfer path for efficiency optimization and detecting foreign objects for safety. The same measurements and processing circuitry used for power management are leveraged for detection, eliminating the need for dedicated detection functionality and reducing overall system complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 effectively identifies the presence of foreign objects, allowing for the mitigation of power transfer issues and preventing undesirable heating, thereby enhancing the safety and efficiency of wireless power transfer.

Implementation Method 1

wireless power transfer from the wireless power transmitter to a wireless power receiver

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS20250096614A1Power transfer accounting for wireless power transfer

Publication Date: 2025.03.20 APPLE INC

AI summary

Transmitters and/or receivers in a wireless power transfer system predict power losses to account for presence of foreign objects.