Comparative evaluation of IPT resonant circuit topologies for wireless power supplies of implantable mechanical circulatory support systems

• Main Authors: Knecht, Oliver, Kolar, Johann W.
• Format: Conference Proceeding
• Language: English
• Subjects: Couplings; Impedance; inductive power transfer; Power generation; Q-factor; Resonant frequency; RLC circuits; thermal modeling; Topology; Transcutaneous energy transfer
• ISSN: 2470-6647
• DOI: 10.1109/APEC.2017.7931166

Today's implantable blood pumps, such as Left Ventricular Assist Devices (LVAD) are powered by means of a percutaneous driveline, which constitutes a severe risk of infection to the patient. Inductive Power Transfer (IPT) technology offers a solution to replace the driveline by a wireless energy link. In this paper, three commonly used IPT resonant circuit topologies are compared regarding power transfer efficiency and heating of the tissue. In the course of the analysis, the main advantages and disadvantages of each topology are identified and as a result it was found that regarding the heating of the tissue, the series-series compensated topology is the most promising solution for Transcutaneous Energy Transfer (TET) systems capable to provide a peak power transmission of up to 30 W. Operated at the resonant frequency using an efficiency optimal control, the series-series compensation topology achieves the highest DC-to-DC power conversion efficiency in the coil coupling and output power range, but requires a higher complexity of the control system, and more important, it shows an increasing secondary side coil power loss with decreasing coil coupling factor. In contrast, the operation near the frequency for load independent voltage gain using a load impedance control technique achieves similar power conversion efficiencies at high coil coupling factors, but offers a lower complexity of the overall TET system. The peak DC-to-DC efficiency measured with a hardware prototype is 97 % at a coil separation distance of 10 mm, a primary and secondary coil diameter of 70 mm and ideal coil alignment. Even at a coil separation distance of 20 mm and an output power of 5W, the efficiency is 90.5 %.