An Inductive Link-Based Wireless Power Transfer System for Biomedical Applications

Abstract

A wireless power transfer system using an inductive link has been demonstrated for implantable sensor applications. The system is composed of two primary blocks: an inductive power transfer unit and a backward data communication unit. The inductive link performs two functions: coupling the required power from a wireless power supply system enabling battery-less, long-term implant operation and providing a backward data transmission path. The backward data communication unit transmits the data to an outside reader using FSK modulation scheme via the inductive link. To demonstrate the operation of the inductive link, a board-level design has been implemented with high link efficiency. Test results from a fabricated sensor system, composed of a hybrid implementation of custom-integrated circuits and board-level discrete components, are presented demonstrating power transmission of 125 mW with a 12.5% power link transmission efficiency. Simultaneous backward data communication involving a digital pulse rate of up to 10 kbps was also observed.

Orientation insensitive power transfer by magnetic resonance for mobile devices

“…The authors of [14] introduced analytical derivation for nearfield power transfer efficiency of loosely coupled inductive links with lateral and angular coil misalignment for three different coil geometries and scenarios, however this did not provide any solution for lateral, angular and rotational misalignment. In [15] showed the effect of changing of coil separation distance, lateral misalignment and angular misalignment, and also simultaneous data communications were demonstrated, this also did not furnish solutions for lateral, angular and rotational misalignment. In addition [16] presented an analytical and finite element method (FEM) analysis of misalignment effects on the WPT and in [17] the focus was on analyzing and optimizing of the energy transfer for inductive coupled system, with emphasis on misalignment analysis.…”

Inductive-Based Wireless Power Recharging System for an Innovative Endoscopic Capsule

“…If the relative position between the two coils is maintained fixed, their surrounding environment is the air and the system does not require the power amplifier to be optimised; therefore, total system efficiency is not compromised. For this reason, a near field resonant inductive coupling was preferred and a parallel resonance for the secondary circuit was chosen, as proposed in [16].…”

“…By using resonant coupled coils, the efficiency of inductive power transfer can be increased, especially by placing the inductors in a resonant LC circuit. For low coupling factors (and consequently low link efficiency), the series resonant topology needs very high secondary coil inductance values to achieve optimum coupling efficiency [16]. This is not possible due to size limitations for the receiver coil, described previously.…”

Advances in Microelectronics for Implantable Medical Devices

“…To minimize radio frequency heating due to tissue absorption, these systems are typically operated below 15 MHz with an achievable data rate up to a few Mbps. Transferred power to the implant typically ranges from 10 mW to 125 mW [89][90][91]. The power transmitted through the tissue should comply with safety standards.…”