Performance Evaluation of Series-Compensated IPT Systems for Transcutaneous Energy Transfer

Today's implantable mechanical circulatory support devices, such as left ventricular assist devices, still rely on a percutaneous driveline, which is a frequent cause of severe infections and which reduces the quality of life for the patients. Inductive power transfer (IPT) is therefore a promising technology to replace the driveline and, hence, reducing the likelihood of an infection. This paper focuses on the series-series compensated IPT system and provides an in-depth comparison of two operating modes, i.e., the operation at resonance and the operation above resonance, and highlights the advantages and disadvantages with respect to the requirements set by the application at hand. In addition, the paper presents the design and the realization of a fully functional transcutaneous energy transfer (TET) implant hardware prototype, which includes the IPT front-end, the control circuit, the backup battery and its charging converter, as well as the communication electronics in a boxed volume of only 10.3 cl. The experimental verification shows that overall dc-dc efficiencies of up to 90% can be achieved for both operating modes when transmitting 25-30 W from the external battery to the implant backup battery, each having a nominal voltage of 14.8 V, using TET coils with 70 mm diameter and 10 mm coil separation distance.