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Optimization and Analysis of Multilayer Planar Spiral Coils for the Application of Magnetic Resonance Wireless Power Transfer to Wearable Devices

Author

Listed:
  • Young-Jin Park

    (Korea Electrotechnology Research Institute, An-San 15588, Korea)

  • Ji-Eun Kim

    (Korea Electrotechnology Research Institute, An-San 15588, Korea)

  • Kyung-Min Na

    (Eta Electronics R&D, Gangnam-gu, Seoul 06121, Korea)

  • Ki-Dong Yang

    (Korea Electrotechnology Research Institute, An-San 15588, Korea)

  • Kyung-Hwan Cho

    (Korea Electrotechnology Research Institute, An-San 15588, Korea)

Abstract

In this study, small multilayer planar spiral coils were analyzed and optimized to wirelessly charge an in-ear wearable bio-signal monitoring device in a wine-glass-shaped transmitter (Tx) based on magnetic resonance wireless power transfer (MR-WPT). For analysis of these coils, a volume filament model (VFM) was used, and an equivalent circuit formulation for the VFM was proposed. The proposed method was applied to design effective multilayer coils with a diameter and height of 6 and 3.8 mm, respectively, in the wearable device. For the coils, a printed circuit board having a 0.6 mm thick dielectric substrate and a 2 oz thick copper metal was used. Moreover, the coils on each layer were connected in series. The dimensions of the double-, four-, and eight-layer coils were optimized for the maximum quality factor (Q-factor) and coupling efficiency. The operating frequency was 6.78 MHz. The optimal dimensions for the maximum Q-factor varied depending on the number of coil layers, pattern width, and turn number. For verification, the designed coils were fabricated and measured. For the four-layer coil, the coupling efficiency and Q-factor using the measured resistance and mutual inductance were 58.1% and 32.19, respectively. Calculations showed that the maximum Q-factor for the four-layer coil was 40.8 and the maximum coupling efficiency was 60.1%. The calculations and measurement were in good agreement. Finally, the entire system of the in-ear wearable bio-signal monitoring device, comprising a wine-glass-shaped transmitter, the designed receiving coil, and a monitoring circuit, was fabricated. The measured dc-dc efficiency of the MR-WPT system was 16.08%.

Suggested Citation

  • Young-Jin Park & Ji-Eun Kim & Kyung-Min Na & Ki-Dong Yang & Kyung-Hwan Cho, 2021. "Optimization and Analysis of Multilayer Planar Spiral Coils for the Application of Magnetic Resonance Wireless Power Transfer to Wearable Devices," Energies, MDPI, vol. 14(16), pages 1-19, August.
    • Handle: RePEc:gam:jeners:v:14:y:2021:i:16:p:5113-:d:617467
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    References listed on IDEAS

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    1. Choong Yeon Kim & Min Jeong Ku & Raza Qazi & Hong Jae Nam & Jong Woo Park & Kum Seok Nam & Shane Oh & Inho Kang & Jae-Hyung Jang & Wha Young Kim & Jeong-Hoon Kim & Jae-Woong Jeong, 2021. "Soft subdermal implant capable of wireless battery charging and programmable controls for applications in optogenetics," Nature Communications, Nature, vol. 12(1), pages 1-13, December.
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    Cited by:

    1. Young-Jin Park, 2022. "Next-Generation Wireless Charging Systems for Mobile Devices," Energies, MDPI, vol. 15(9), pages 1-4, April.
    2. Wang, De'an & Zhang, Jiantao & Cui, Shumei & Bie, Zhi & Chen, Fuze & Zhu, Chunbo, 2024. "The state-of-the-arts of underwater wireless power transfer: A comprehensive review and new perspectives," Renewable and Sustainable Energy Reviews, Elsevier, vol. 189(PA).
    3. Kai Song & Yu Lan & Xian Zhang & Jinhai Jiang & Chuanyu Sun & Guang Yang & Fengshuo Yang & Hao Lan, 2023. "A Review on Interoperability of Wireless Charging Systems for Electric Vehicles," Energies, MDPI, vol. 16(4), pages 1-22, February.

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