A Highly Efficient Fully Integrated Active Rectifier for Ultrasonic Wireless Power Transfer

Ultrasonic wireless power transfer (WPT) has been proved to be a promising approach to power biomedical implants. To extract the energy generated from the transducer, a rectifier is typically required. Previous inductor-based rectifiers (SSHI and SECE) require a large off-chip inductor to achieve good performance, which is not desired for miniaturization and safety reasons. Synchronized switch harvesting on capacitors (SSHC) rectifiers have been proved to achieve high performance without inductors; however, they are mainly designed for low-frequency kinetic energy harvesting. In this paper, an improved SSHC rectifier is designed to achieve a fully integrated design with all flying capacitors implemented on-chip. The proposed SSHC rectifier can properly operate at ultrasonic excitation frequency (100KHz) with precise switching time control and ultrafast voltage flipping techniques. In addition, an on-chip ultralow-power LDO allows the system to be self-sustained. The system is designed in a TSMC 180nm BCD technology and post-layout simulation results are presented.