| dc.description.abstract | The modern healthcare industry relies on the use of implantable monitoring devices to obtain potentially life-saving data. This has led to the necessity for small, long-lasting batteries to be used in these devices. In order to replace a device’s battery, patients often undergo invasive surgery. This surgery can be costly and physically strenuous for the patient; thus, there is a desire to minimize the frequency of battery replacement. The goal of this research is to develop an integrated circuit that can supply harvested energy to an implantable monitoring device so as to extend implant batteries’ lifetime. These monitoring devices are often implanted just below the skin of a patient, where natural temperature gradients exist. Using the well-known physical principle called the Seebeck effect, these temperature gradients can be exploited to produce electrical power by using a specialized device called a thermoelectric generator. With some additional circuitry, this harvested energy can be used in place of the battery to supply power to the implanted device. Such circuitry includes a switching regulator with a PWM controller, an oscillator, and digital logic. The thermoelectric generator can harvest enough energy to power the device, but the voltage produced is generally too low to be used. Thus, the voltage must be stepped up to a higher value. The switching regulator topology best suited for this purpose is the DC-DC boost converter due to its high efficiency. However, the amount of power harvested is small, so this paper has a major emphasis on power consumption optimization for each circuit block added. Also, the boost converter must use feedback in order to regulate the output to a constant voltage, so a controller was designed and implemented for this purpose. An additional feedforward path was added to perform an impedance match between the source resistance and the boost converter to reduce the charge time of the output capacitor. An oscillator was needed to switch transistors in the boost converter and provide the synchronicity needed in the digital logic blocks. Finally, the last circuitry developed was digital logic to control the startup procedure and choose to use either the harvested energy or the battery to power the implanted device. This paper will discuss the design procedure for each of the mentioned circuit blocks and provide the results of the research conducted. | |
