Charging Surface Impedance Detection for Foreign Metal Objects
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Solution Overview
Problem
Conductive wireless charging systems face challenges in detecting foreign conductive objects on charging surfaces, leading to potential overheating issues due to imperfect alignment and interference, which existing solutions fail to address effectively without increasing complexity and cost.
Innovation Solution
A method involving a charging device with conductive charging surfaces and a reporting device, where one surface is put in a determined impedance state to measure voltage temporal evolution, allowing for the detection of foreign objects by comparing measured voltage curves to calibrated values, using a Thevenin impedance adapter and current surge protection circuits to prevent overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conductive wireless charging is used to eliminate wires and improve convenience, then ease of operation is improved, but foreign conductive objects may be unintentionally placed on charging surfaces causing overheating and safety issues
Solution Approach 1:
The system performs a preliminary detection phase before activating full charging power. The detection circuit measures equivalent resistance of objects on the charging surface to identify foreign conductive objects, preventing overheating before it occurs by stopping or reducing power delivery when foreign objects are detected
2Reliability
If detection systems are added to identify foreign objects, then safety is improved, but device complexity increases
Solution Approach 1:
The detection circuit is integrated into the existing charging device infrastructure, using the same charging surfaces and control circuits for both charging and detection functions. The equivalent resistance measurement capability is built into the charging control logic, eliminating the need for separate dedicated detection hardware
Solution Approach 2:
The system uses its own charging circuitry to perform detection functions. The charging device measures equivalent resistance through its existing power delivery paths and control circuits, making the detection system self-contained and eliminating the need for external or additional complex detection equipment
3Measurement precision
If the charging device monitors voltage temporal evolution to detect foreign objects, then measurement precision is improved, but loss of time occurs during detection
Solution Approach 1:
The system performs voltage temporal evolution measurements at periodic intervals during the charging process. Rather than continuous monitoring, the detection circuit samples voltage at predetermined time points to track the evolution pattern, achieving accurate foreign object detection while minimizing time loss through efficient periodic sampling
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 method effectively detects foreign conductive objects with high equivalent resistance, preventing overheating while maintaining low complexity and cost, ensuring safe and efficient charging operations.
Implementation Method 1
measuring a voltage temporal evolution across one of said charging surfaces while the negative charging surface is put in said determined impedance state; the presence of the foreign conductive object being determined based on said measure
Data Source
AI summary
The invention relates to a method for detecting the presence of a foreign conductive object (12) on the charging surfaces of a charging device (1), said charging surfaces (2, 3) being configured to cooperate with a reporting device (4) equipped with at least two power terminals (5, 6) so as to have a contact between the reporting device's power terminals (5, 6) and at least two charging device's charging surfaces (2, 3), the method comprising the steps of:a) providing an appropriate power to the conductive charging surfaces (2, 3) so as to charge an article (7) connected to the reporting device (4);b) while providing said appropriate power, putting one of said charging surfaces (2, 3) in a determined impedance state, and measuring a voltage temporal evolution across said charging surfaces (2, 3) while said charging surfaces (2, 3) is put in said determined impedance state; the presence of the foreign conductive object (12) being determined based on said measure.