A novel SPICE implementation of MPPT technique for implantable solar powered cardiac biosensors

This paper presents a low power implantable solar power supply for battery operated cardiac biosensors. The main focus of this paper is to generate power from a photovoltaic (PV) array placed beneath the skin to replenish the depleting battery of the implantable cardiac biosensors. The new methodology extracts maximum power from the implanted PV array receiving near infrared light (NIR) through the skin from the external source and relies completely on power produced by implanted PV array for its operation. The proposed scheme employs a novel voltage based maximum power point tracking (MPPT) technique that uses the virtual open-circuit voltage to regulate the supply continuously. The implementation uses PV array modeled in SPICE that provides 10-25mW power for a current range of 6-14mA. Simulations show that the implantable supply produces sufficient power and voltage to charge the battery of low power implantable cardiac biosensors like pacemaker.