NFC Transmitter Magnetic Field Strength Adjustment for Passive Device Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wireless charging systems fail to reliably detect and differentiate between passive NFC devices and active NFC devices, leading to potential damage to RFID cards due to the strong magnetic fields used for charging, as they cannot accurately distinguish between physical and emulated RFID cards.
Innovation Solution
A wireless charging device that employs a request-response communication process using an NFC transmitter to identify passive NFC devices by sending a request signal and adjusting the magnetic field strength to ensure that passive devices can respond, thereby distinguishing them from active devices with internal power sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a strong alternating magnetic field is used for wireless charging, then charging power is improved, but passive NFC devices in the charging area may be damaged
Solution Approach 1:
The system performs detection of passive NFC devices before initiating the wireless charging process. The NFC transmitter sends a detection signal and checks for responses from passive NFC cards in the charging area. Only after confirming no passive NFC devices are present does the system proceed to generate the strong alternating magnetic field for charging, thus preventing damage while maintaining charging power.
2Measurement precision
If an NFC reader is used to detect NFC cards, then detection capability is improved, but the system cannot reliably distinguish physical NFC cards from emulated NFC cards
Solution Approach 1:
The system changes the magnetic field strength parameter during the detection process. First, a strong magnetic field is used to detect all NFC devices. Then, the field strength is reduced to a lower level where only active NFC devices with internal power sources can respond. Passive NFC cards cannot respond at this lower field strength, allowing the system to distinguish between physical and emulated cards based on their response capability at different field strengths.
3Reliability
If the charging process is denied when NFC cards are detected, then safety is improved, but charging functionality is reduced
Solution Approach 1:
The system applies different quality levels to different detection scenarios. When only active NFC devices are detected, charging proceeds normally. When passive NFC devices are detected, charging is denied. The system locally adapts the charging behavior based on the specific type of NFC device detected, maintaining safety while preserving charging functionality in safe scenarios.
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 provides a reliable and protocol-independent means to identify passive NFC devices, preventing damage by reducing or denying the charging process when passive devices are detected, ensuring safe operation and accurate differentiation from active NFC devices.
Implementation Method 1
an energy supplier generates an alternating magnetic field by means of a charging coil or an array of charging coils. The mobile device comprises a reception coil and has to be situated in the alternating magnetic field during charging. The alternating magnetic field induces a current in the reception coil of the mobile device
Implementation Method 2
The NFC transmitter is configured to provide during the predefined request response communication process an alternating magnetic field at the predefined magnetic field strength that is higher than a predefined support magnetic field strength necessary to drive passive NFC devices
Data Source
Figure 1
Figure 2
AI summary
The invention is concerned with a wireless charging device (1) comprising an NFC-transmitter (12) configured to detect a NFC-device (3, 8) in a predefined space (9) related to a charging coil (4) by means of a predefined request-response-communication-process with the NFC-device (3, 8), wherein the NFC-transmitter (12) is configured to provide during the predefined request-response-communication-process an alternating magnetic field (5) at a predefined magnetic field strength (H1) and to then individually address the detected NFC-device (3, 8) by means of a request-signal (TX2) during a following predefined identification-communication-process. The invention is characterized in that the NFC-transmitter (12) is configured to provide during the predefined identification-communication-process an magnetic field (5) at a predefined reduced magnetic field strength (H2), and to identify the detected NFC-device (3, 8) as a passive NFC-device (8), if a predefined response signal (RX2), requested by the request signal (TX2) during the predefined identification-communication-process is missing.