Mid-range wireless power transfer with segmented coil transmitters for implantable heart pumps

In wireless power transfer systems, the transmitting coil dimensions can substantially affect the transmission range and alignment sensitivity. We found that a transmitting coil with larger inner and outer diameter has a wider transmission range and lower alignment sensitivity. Thus, we developed a larger coil (24×30 cm2) designed to be embedded in the back of a vest to power DC pumps for artificial hearts or LVADs. To significantly reduce the required voltage, the coil was divided into 8 segments with resonant capacitors. The coil was operated at 6.78 MHz and evaluated with a 5.3-cm diameter receiving coil. A circuit model for the energy coupling coils was developed to predict the output power and efficiency. Having a coil separation of 7.7 cm, the output power and efficiency of the energy coupling coils are higher than 48 W and 80%, respectively. The system was experimentally tested with a DC pump, demonstrating that the proposed coil segmentation technique can significantly reduce the transmitter voltage to a safe level (∼10 Vrms).