An efficient wireless power transfer system design for deep brain stimulation

Reliable power supply to implantable active medical devices is important in biomedical applications such as Deep Brain Stimulation (DBS) systems. Conventional DBS devices are powered by batteries that often require surgical interventions, which brings problems such as infection risk and patient discomfort. In this thesis, direct cranial implantation of a wireless power transfer (WPT) system to DBS devices is proposed to avoid these problems. This approach eliminates the need for cables passing through the neck and smaller batteries can be used. In this way, patient comfort can be increased and different infection risks can be minimized. In addition, long-term economic benefits for the national economy can be achieved by reducing operating room crowding. In this thesis, a new DBS device designed for direct cranial implantation, which has been studied in the literature in recent years, and a KGT system with a hybrid topology suitable for this device are developed and analytically analyzed. The study focuses on conventional two-coil LCC-C and four-coil LCC-C-C-C-C topology. In this context, spiral coils are modeled with 3D finite element method in ANSYS environment and LCC-C and LCC-C-C-C-C circuit designs are analyzed. According to the experimental power transfer efficiency results obtained in the tissue environment, the two-coil system designed on FR4 offers 6.8% efficiency at 5mm distance, while the four-coil system achieved 25% efficiency. Also, in the case of a horizontal shift of 5mm at a vertical distance of 5mm, the efficiency of the two-coil system decreased to 4.41%, while the four-coil system remained at 16.9%. The AC voltage obtained at the receiver side was converted to DC and the 1S LiPo battery was charged in CC-CV mode. A DBS prototype was designed to generate the fundamental waveforms and a mobile application was developed to control the parameters of the stimulation signals. A current of ⁓7 mA was drawn from the battery when the Bluetooth, control and stimulation circuitry was active. SAR analysis for clinical applicability showed safe results at 0.415 W/kg.