Wireless Charging Coil Impedance Detection for NFC Protection
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Solution Overview
Problem
Existing wireless charging systems lack effective protection mechanisms to prevent damage to sensitive electronic devices like NFC and RFID cards, which can be affected by the high amplitude magnetic fields generated during charging.
Innovation Solution
Incorporating an impedance detection circuit and a proximity detection circuit that selectively generate and adjust the wireless charging field based on detected impedance changes, reducing or disabling the charging field when sensitive devices are present to prevent damage, and using a shared coil configuration with isolation circuitry for efficient detection and charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a wireless charging field is generated with high transmit power, then charging efficiency is improved, but sensitive electronic devices (NFC/RFID cards) may be damaged by the high amplitude magnetic field
Solution Approach 1:
The system performs preliminary detection of NFC/RFID cards before initiating high-power wireless charging. The proximity detection circuit scans for sensitive devices in advance, and if detected, prevents activation of the high-power charging field, thereby avoiding damage while allowing efficient charging when no sensitive devices are present
Solution Approach 2:
The system continuously monitors the charging environment and adjusts transmit power based on detected conditions. When NFC/RFID cards are detected, the system provides feedback to reduce or disable the charging field, creating a closed-loop control that balances charging efficiency with device safety
2Reliability
If an impedance detection circuit is added to detect impedance changes, then proximity of sensitive devices can be detected, but device complexity increases
Solution Approach 1:
The impedance detection circuit serves multiple functions: it detects the presence of NFC/RFID cards, monitors charging status, and provides safety feedback. By making this circuit multi-functional, the patent reduces the need for separate dedicated detection circuits, thereby limiting the increase in overall device complexity while maintaining high detection reliability
Solution Approach 2:
The patent combines the impedance detection functionality with existing wireless charging circuitry. The same coil and control circuitry used for charging are also utilized for detection purposes, merging multiple functions into unified circuit blocks to minimize additional complexity
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 solution effectively protects NFC and RFID devices by reducing or disabling the wireless charging field when sensitive devices are detected, ensuring safe operation and maintaining charging efficiency for other devices.
Implementation Method 1
a wireless charging circuit configured to selectively generate a wireless charging field
Implementation Method 2
an impedance detection circuit coupled to the wireless charging circuit and configured to detect an impedance change corresponding to the wireless charging field
Implementation Method 3
a proximity detection circuit configured to selectively detect proximity of one or more electronic devices that are prone to damage by the wireless charging circuit
Data Source
AI summary
Certain aspects of the present disclosure are generally directed to apparatus and techniques for protecting electronic devices that may be prone to damage by wireless charging fields. For example, the apparatus may include a wireless charging circuit configured to selectively generate a wireless charging field and an impedance detection circuit coupled to the wireless charging circuit and configured to detect an impedance change corresponding to the wireless charging field. In this case, a proximity detection circuit may selectively detect proximity of one or more electronic devices that are prone to damage by the wireless charging circuit. In some aspects, detecting the proximity of the one or more electronic devices is activated based on detecting the impedance change, and wherein generating the wireless charging field comprises reducing a transmit power of the wireless charging field based on detecting the impedance change.