A single-inductor 0.35µm CMOS energy-investing piezoelectric harvester

Because miniaturized systems store little energy, their lifespans are often short. Fortunately, vibrations are consistent and abundant in many applications, so ambient kinetic energy can be a viable source. Vibrations induce the charges in piezoelectric transducers to build electrostatic forces that damp vibrations and convert kinetic energy into the electrical domain. The shunting switches and switched-inductor circuit of bridge rectifiers in [1-2] increase this output energy by extending the damping (i.e., harvesting) duration within a vibration cycle. Because the output voltages of bridge rectifiers clamp and limit the electrical damping forces built, switched-inductor converters in [3-4], whose damping voltages can exceed their rectified outputs, draw more power from vibrations. Still, electrical-mechanical coupling factors in tiny transducers are low, so electrical damping forces (i.e., voltages) remain weak. Investing energy into the transducer can increase this force, but unlike in [5-6], which demand multiple inductors and high-voltage sources, the system presented here invests energy with only one inductor at low voltages.