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Project

More and more, small battery-driven devices such as wearables are increasingly available. With their low power consumption, the challenge is to use NFC technology for battery charging

NFC wireless charging evaluation

Objective

To characterize and determine the performance of NFC Wireless charging while considering small antennas and identifying possible drawbacks.

Description

The aim of this project was to obtain meaningful data regarding the possibility of using NFC technology to charge small battery driven devices. We used the Connected Device hardware for this study since it is a small wearable powered with a 45mA/h battery.

Initially, we built an energy harvesting circuit connected to an NFC antenna. As a first step, we characterized the performance of this setup with several commercial readers. The results showed us that the solution gathered enough power to charge the battery. However, the system is very sensitive to the position of the NFC antenna in relation to the charger antenna.

The next step was to embed the harvesting circuit together with the NFC antenna into the Connected Device. To protect the Connected Device and achieve a more stable signal to feed the battery, we also added a limiter. The overall performance was again characterized against several commercial readers.

We concluded that NFC technology is suitable for wireless power transfer for small battery-driven devices such as wearables. The final setup must be considered for reaching an optimum charging performance.

Further work is currently undertaken around this study.

Technology & tools used

  • NFC technology
  • Network analyzer
  • PCB prototyping
  • Oscilloscope and multimeters for signal characterization

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