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Implantable medical devices like the pacemakers are used to generate electric pulses for smooth stimulation of heart muscles. A pulse generator electronic circuit along with a controller is used as a part of the pacemaker device to produce controlled pulse signals. The objective of this research is to design, and modeling of a high-frequency supercapacitor based pulse generator for implantable medical electronics. The high frequency-supercapacitor used is based on vertically grown graphene on carbon microfiber sheet. The architecture has three main components: 1) the power source, 2) the pulse generator and 3) the control system for the pulse generator. There are two sources of power for the device, a battery, and a piezoelectric energy harvester. A bi-directional buck-boost DC-DC converter has been designed along with a robust feedback controller to control the flow of power between the energy sources and the pulse generator circuit. The device is designed to generate output pulses in the range of 0-15V which is ideal for medical devices such as heart pacemakers, defibrillators etc. The pulse generator circuit is designed to operate in two modes. A control system has been designed to operate the array of five supercapacitors in two modes. In the first mode, the circuit uses only desired number of supercapacitors depending on the total output voltage and would operate for the frequencies less than 1 KHz. The second mode will use all the supercapacitors in the array to produce the desired output voltage and this mode will operate for a pulse requirement more than 1 KHz. The wide range of operating frequencies of this circuit makes it to be applicable for many implantable medical applications. The supercapacitor model in the circuit is a series RC circuit where the resistance and the capacitance are dynamically calculated and injected directly from the data obtained from Impedance Spectroscopy measurements performed on the physical supercapacitor. This makes the model to function closely similar to that of the real supercapacitor circuit. All the circuits and components have been modeled and simulated in MATLAB-Simulink.



Vertically grown graphene on carbon microfibers, Pacemakers