## Abstract

This paper introduces a 6.78-MHz wireless power transfer (WPT) system for implantable medical devices (IMDs). The proposed dual-output resonant current-mode (RCM) rectifier cumulates energy from loosely-coupled coils and generates two output voltages (V<inline-formula> <tex-math notation="LaTeX">$_{\mathrm{H}}$</tex-math> </inline-formula> <inline-formula> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 3-V, V<inline-formula> <tex-math notation="LaTeX">$_{\mathrm{L}}$</tex-math> </inline-formula> <inline-formula> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 1.8-V) regulated by adaptive power control (APC) and local-loop power control. Due to transmission power regulation (TPR), the transmitter (<inline-formula> <tex-math notation="LaTeX">$T_{X})$</tex-math> </inline-formula> delivers appropriate power to the receiver (<inline-formula> <tex-math notation="LaTeX">$R_{X})$</tex-math> </inline-formula> to realize global-loop power control. Thus, the power transfer efficiency (PTE) is improved, especially under light load. Furthermore, zero-voltage switching and zero-current switching techniques enhance R<inline-formula> <tex-math notation="LaTeX">$_{X}$</tex-math> </inline-formula> power conversion efficiency (PCE). <inline-formula> <tex-math notation="LaTeX">$T_{X}$</tex-math> </inline-formula> and <inline-formula> <tex-math notation="LaTeX">$R_{X}$</tex-math> </inline-formula> chips were fabricated in a 0.18-<inline-formula> <tex-math notation="LaTeX">$\mu $</tex-math> </inline-formula>m CMOS process. The measurement results show that the proposed WPT system successfully regulates outputs at V<inline-formula> <tex-math notation="LaTeX">$_{\mathrm{H}}$</tex-math> </inline-formula> <inline-formula> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 3-V and V<inline-formula> <tex-math notation="LaTeX">$_{\mathrm{L}}$</tex-math> </inline-formula> <inline-formula> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 1.8-V at a 1.5-cm coupling distance. With the proposed TPR, PTE is improved by 28.2% at P<inline-formula> <tex-math notation="LaTeX">$_{\mathrm{TOTAL}}$</tex-math> </inline-formula> <inline-formula> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 1.6-mW, and input power is reduced by 94.8% at P<inline-formula> <tex-math notation="LaTeX">$_{\mathrm{TOTAL}}$</tex-math> </inline-formula> <inline-formula> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 1-mW. The measured peak PCE and peak PTE are 85.1% and 31.3% at a coil distance of 10-mm, respectively.

Original language | English |
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Pages (from-to) | 1-13 |

Number of pages | 13 |

Journal | IEEE Transactions on Circuits and Systems I: Regular Papers |

DOIs | |

State | Accepted/In press - 2023 |

## Keywords

- Coils
- global-loop power control
- Loading
- Power control
- Receivers
- Rectifiers
- regulating rectifier
- Regulation
- resonant coupling
- resonant current-mode
- Transmission power regulation
- Voltage control
- wireless power transfer