Inductive Power Transfer Control for Foreign Object Detection
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Solution Overview
Problem
Existing inductive coupler systems face challenges in accurately detecting metallic foreign objects during power transfer, which can lead to heating and potential hazards, and are often dependent on distance and power levels.
Innovation Solution
A system and method that uses a control unit to record and compare primary and secondary power data, determining primary target power data through a power characteristic, allowing for precise detection of foreign objects by comparing actual primary power data with the target data, and adjusting power levels to prevent heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If inductive power transfer is performed between primary device and secondary device, then power can be transferred contactlessly, but metallic foreign objects in the electromagnetic field may cause heating and safety hazards that are difficult to detect
Solution Approach 1:
The system performs preliminary foreign object detection by comparing actual primary power data with target primary power data (calculated from secondary power data and power characteristic) before and during power transfer. This preliminary detection identifies foreign objects that would otherwise cause heating, allowing the system to prevent or reduce power transfer to affected areas.
Solution Approach 2:
The system continuously monitors both primary power data and secondary power data, compares actual primary power with target primary power (derived from the power characteristic), and uses this feedback to detect foreign objects. The detection result feeds back to control the power transfer, adjusting or interrupting power delivery when foreign objects are detected, thereby preventing heating hazards while maintaining contactless operation.
2Difficulty of detecting and measuring
If foreign object detection is performed using fixed limit values for primary-side input power, then detection can be implemented, but detection accuracy is limited and may not work reliably across various distances and power levels
Solution Approach 1:
The system replaces fixed limit values with dynamic target primary power data that adapts to changing operating conditions. The target primary power is calculated in real-time based on secondary power data and a power characteristic (reference primary power data as a function of reference secondary power data). This dynamic approach allows accurate foreign object detection across various distances and power levels, as the detection threshold automatically adjusts to match expected power transfer conditions.
Solution Approach 2:
The system changes the detection parameter from a fixed primary power limit to a variable target primary power derived from the power characteristic. By establishing a functional relationship between primary and secondary power through the power characteristic, the system can accurately detect foreign objects regardless of distance or power level variations, as the detection criterion adapts to the actual operating parameters.
3Reliability
If power transfer is interrupted when fixed limit values are exceeded, then safety can be maintained, but false interruptions may occur due to distance and power level variations
Solution Approach 1:
The system uses dynamic target primary power data based on the power characteristic to determine when to interrupt power transfer, rather than fixed limit values. This allows the system to maintain safety by detecting actual foreign objects while avoiding false interruptions caused by normal variations in distance and power level. The power transfer only interrupts when genuine foreign objects are detected, maintaining productivity while ensuring safety.
Solution Approach 2:
The system continuously compares actual primary power with target primary power (calculated from secondary power and power characteristic) and uses this feedback to make intelligent decisions about power transfer continuity. This feedback mechanism distinguishes between normal power variations and actual foreign object presence, preventing false interruptions while maintaining safety, thus preserving productivity without compromising reliability.
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 system effectively identifies foreign objects across various distances and power levels, minimizing heating risks and hazards by dynamically adjusting power transfer, ensuring operational safety and efficiency.
Implementation Method 1
Power can be transferred inductively between a primary device (transmitter) and a secondary device (receiver) via an electromagnetic field
Data Source
AI summary
An inductive power transfer system is provided, comprising a primary device, a secondary device, and a control unit, wherein the primary device is arranged and designed to inductively transfer power via a primary oscillating circuit to a secondary oscillating circuit of the secondary device during the transfer of power, wherein the control unit is designed to record secondary power data of the secondary device and to determine primary target power data using a power characteristic and the recorded secondary power data, wherein the power characteristic comprises reference primary power data as a function of reference secondary power data, wherein the control unit is designed to record primary power data of the primary device and to detect a foreign object using a comparison of the primary target power data with the primary power data.