Design and Development of an Ultrasonic Power Transfer System for Active Implanted Medical Devices

Abstract

Ultrasonic transcutaneous energy transfer (UTET) is a promising method for wireless power transfer to active implanted medical devices (AIMDs). Traditionally, AIMDs have relied on electromagnetic induction for wireless power transfer. However, when it comes to miniaturized power transfer devices, UTET has been shown to outperform EM based devices. In order to further the development of UTET devices for AIMDs, there are a number of design challenges which need to be addressed. This thesis work focuses on three key areas: i) the design and development of a feedback protocol for maintaining consistent UTET power transfer efficiency (PTE) across varying tissue separations, ii) the design and development of a high efficiency, high-frequency, low-power transmitter for driving the transmit side of a UTET link, and iii) the design and development of a high-efficiency rectifier and charging circuit for the receive side of a UTET link. The developed protocol for maintaining consistent PTE is shown to be extremely effective in regulating efficiency despite random changes in tissue separation; the protocol is tested in a realistic power transfer scenario through porcine tissue subject to random changes in inter-transducer separation distance. The designed transmitter is shown to operate with a peak efficiency of 93% at 1.28 MHz and an output power < 200mW. The designed receive circuitry is shown to have a full-wave rectification efficiency >90%; when paired with a high-efficiency DC-DC converter integrated circuit, the combined efficiency is ~70-80% for received powers > 40mW.