Smartwatch Strap Wireless Power Transfer System with Flexible PCB Coil and Shielding Material
In this paper, we designed and demonstrated a smartwatch strap wireless charging system for the first time. First, we designed a flexible printed circuit board (PCB) coil, shielding material, and receiver (Rx) circuit in a watchstrap. In the design process, we proposed a model for the flexible PCB coil with a bending radius of 40 mm and shielding materials. We used a flexible PCB coil that has 215 µm thickness with dimensions of 54.5 x 16 mm. In addition, ferrite core and sheet are applied on the transmitter (Tx) and Rx coils. We verified the proposed model through a three-dimensional (3-D) electromagnetic (EM) simulation and measurement in the frequency and time domains. The proposed flexible PCB coil inductance modeling results showed 7.5% and 3.4% errors when compared to the 3-D EM simulation and measurement results, respectively. Furthermore, we demonstrated the smartwatch strap wireless charging system using an LG Watch Urbane. A resonance frequency of 100 kHz with the series-series tuning topology is used in accordance with the Qi specifications. Finally, we achieved 30% dc-dc power transfer efficiency and exposed magnetic field of 270 mG, 1 cm away from the system through measurements.
S. Jeong et al., "Smartwatch Strap Wireless Power Transfer System with Flexible PCB Coil and Shielding Material," IEEE Transactions on Industrial Electronics, vol. 66, no. 5, pp. 4054-4064, Institute of Electrical and Electronics Engineers (IEEE), May 2019.
The definitive version is available at https://doi.org/10.1109/TIE.2018.2860534
Electrical and Computer Engineering
Electromagnetic Compatibility (EMC) Laboratory
Keywords and Phrases
Electromagnetic fields (EMFs); flexible printed circuit board (PCB) coil modeling; magnetic shielding material; smartwatch strap; wireless power transfer (WPT)
International Standard Serial Number (ISSN)
Article - Journal
© 2019 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.
01 May 2019