Title:  Tiny Piezoelectric Energy Harvesting CMOS Charger

Committee: 

Dr. Rincon-Mora, Advisor     

Dr. Hunt, Chair

Dr. Ayazi

Abstract:

The objective of this research is to study, evaluate, design, build, test, and assess energy-harvesting CMOS battery chargers that draw and output the most power possible from ambient motion with centimeter-scale piezoelectric transducers that can fit on wireless microsensors. Unfortunately, small transducers draw little power, chargers consume energy, and vibration strength varies. Small transducers, however, are so underdamped that the current they output is nearly unaffected by the power they supply. So raising their voltages increases the power they draw from vibrations. Except, breakdown voltage limits the extent that this is possible, which is why balancing voltages near or below this limit is important. And since switched inductors burn more power when they transfer more energy, steering power directly into the battery can reduce losses, and in consequence, raise output power. This research therefore proposes to explore how to raise and balance voltages and transfer power so piezoelectric transducers can deliver more power, chargers can lose less energy, and breakdown voltage can be less constraining. With higher input power, lower losses, and less constraints, energy-harvesting chargers can sustain more functions across longer life cycles for a wider range of wireless microsensor applications, such as smart homes, hospitals, factories, bionics, and so on.