TET for Implantable Mechanical Heart Support Systems

Inductive Power Transfer (IPT) technology is a promising solution for poweringimplantable mechanical circulatory support systems, due to the elimination of the percutaneous driveline, which is still the major cause of severe infections. However, at the present time, no Transcutaneous Energy Transfer (TET) system is commercially available and ready for long-term use. Specifically the heating of the tissue due to power losses in the TET coils and the implantedelectronic components are a major problem. The focus of this paper is, therefore, on the design and realization of a highly efficient TET system and the minimization of the power losses in the implanted circuits in particular.

Parameter sweeps are performed in order to find the optimal energy transmission coil parameters. In addition, simple and meaningful design equations for optimal load matching are presented together with a detailed mathematical model of the power electronic stages. To achieve highest efficiencies, a high frequency self-driven synchronous rectifier circuit with minimized volume is developed. Extensive measurements are carried out to validate the mathematical models and to characterize the performance of the prototype system. The optimized system is capable of transmitting 30W of power with an efficiency of greater than 95 %, even at a coil separation distance of 20mm (0.79 in) and 70mm (2.76 in) coil diameter.