A 200.2-mW Wireless Power Transfer System with Hybrid SC-/RC-LSK and Triple Regulated Outputs Achieving 66.1% E2E Efficiency

Abstract

This paper presents a $6.78-\text{MHz}$ wireless power transfer (WPT) system for implantable biomedical devices. The receiver (RX) features a compact single-stage triple-output rectifier that delivers three regulated DC outputs ($1 \mathrm{V}, 2 \mathrm{V}$, and 3 V) using only two power transistors and two buffer capacitors. A novel load-shift-keying (LSK) technique, hybridizing the shortcircuit (SC) LSK and resistive-circuit (RC) LSK, is proposed, achieving low-loss power-data backscattering and fully integrated global power regulation between the RX and transmitter (TX) chips. TX and RX chips were designed and fabricated in a $\mathbf{1 8 0}-\mathbf{n m}$ BCD process. Measurement results show that the system provides three regulated DC outputs at $1 \mathrm{V}, 2 \mathrm{V}$, and 3 V, respectively, with unnoticeable cross-regulations and load transients. Supplied by a $3.3-\mathrm{V}$ input at TX, it achieves 200.2 mW peak output power, 66.1 % peak end-to-end (E2E) power efficiency, and up to 27.3 % E2E-efficiency enhancement thanks to global power regulation.