Wireless Energy Transfer System Based On 3D MEMS Litz Double Coils

Over the last decade, implantable electronic devices have been widely used in health, medical, and consumer application, and had a great impact on people’s lives. Some implants utilize rechargeable batteries, though a lot of battery charging methods were developed, however their applications are confined owing to the total charge storage ability and number of recharge cycles of the batteries. Moreover, they require large incisions for implantation, making them infeasible for minimally invasive surgeries or endoscopic procedures.Wireless magnetic resonant energy transfer system shows more superiority in energy transfer efficiency and relative position parameters than that of inductive coupling system. A system using resonant coupling can be nearly omnidirectional and efficient, with low interference and low losses into environmental objects, irrespective of the geometry of the surrounding space. It has become one of best method to supply power for implantable electronic devices.In this paper, a 3D MEMS Litz Double Coils (3D-MLDC) with two identical integrated MEMS coils was proposed and the corresponding theoretical model for inductance, AC resistance, and quality factor was built up. Based on the theoretical model,3D-MLDC with different numbers of strands and turns were designed and simulated using MATLAB to study the effects of geometric parameters on the coil performance. Several 3D-MLDC with different numbers of strands and turns were wound and measured by Keysight impedance analyzer E4990 A to validate the proposed theoretical model. The measured results of the 3D-MLDC were in agreement with the theoretical model.At last, two same 3D-MLDCs with 6 mm diameters were applied to set up the wireless energy transfer system. A Class-E amplifier with inverter driver was designed using power tube and used as a transmitter. Discrete components were used to set up the rectifier and regulator circuit which comprised receiver to provide a regulated output. The maximum energy transfer efficiency is 21.24% at the working frequency of 13.56 MHz when the transmission distance is 5mm with a load of 100O. The output voltage is 1.477V which is equivalent to a power of 21.82mW is obtained.