NFC Charging Control Using Resonant Frequency Detection
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Solution Overview
Problem
Existing NFC devices risk damaging passive NFC devices due to unintentional exposure to charging units not designed for them, leading to potential damage from excessive power transfer.
Innovation Solution
An NFC device with a detection unit to identify passive NFC devices by analyzing the relationship between resonant frequency and field strength, preventing or reducing power transfer if a non-linear relationship is detected, and allowing charging if a linear relationship is present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the charging unit transfers power to external devices without detection, then charging functionality is available, but passive NFC devices may be damaged due to excessive power transfer
Solution Approach 1:
The detection unit performs preliminary identification of passive NFC devices before the charging unit activates power transfer. By detecting the presence of passive NFC devices in advance and preventing charging to them, the system avoids damage while maintaining safety. This preliminary action resolves the contradiction by ensuring reliability through pre-checks without requiring complex real-time control mechanisms during charging.
2Reliability
If the charging unit reduces power for all external devices, then passive NFC devices are protected, but active devices experience reduced charging efficiency
Solution Approach 1:
The system applies different power transfer strategies to different types of external devices based on local characteristics. Passive NFC devices receive no power transfer (protected mode), while active devices receive full power transfer (charging mode). This localized differentiation resolves the contradiction by protecting passive devices without compromising charging efficiency for active devices, as each device type receives treatment tailored to its specific needs.
3Measurement precision
If the detection unit analyzes resonant frequency relationships, then accurate device identification is achieved, but system complexity and measurement time increase
Solution Approach 1:
The detection unit uses feedback from resonant frequency measurements at different field strengths to identify passive NFC devices. By measuring resonant frequency relationships and using this feedback to determine device type, the system achieves accurate identification. This feedback mechanism resolves the contradiction by providing precise device differentiation through systematic measurement analysis, balancing accuracy with manageable system 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
Prevents damage to passive NFC devices by ensuring appropriate power levels are used, distinguishing between passive and active devices through resonant frequency analysis, thereby safeguarding against quick damage.
Implementation Method 1
a primary device may generate a radio frequency (RF) field at a frequency of 13.56 MHz to power a secondary device
Implementation Method 2
the detection unit is configured to determine whether or not a relationship between a resonant frequency of the external device and a field strength of the NFC device can be approximated as a linear relationship
Data Source
AI summary
In accordance with a first aspect of the present disclosure, a near field communication (NFC) device is provided, comprising: an antenna configured to enable wireless communication with an external device; a charging unit configured to charge the external device by transferring power to said external device through said antenna; a detection unit configured to detect whether the external device is a passive NFC device; a controller configured to control the charging unit in dependence on an output of the detection unit, wherein said output indicates whether the external device is a passive NFC device. In accordance with a second aspect of the present disclosure, a corresponding method of operating a near field communication (NFC) device is conceived.