Energy-investment schemes for increasing output power in piezoelectric harvesters

Energy and power in tiny batteries are often insufficient to sustain the demands of a wireless microsystem for extended periods. Piezoelectric transducers are viable alternatives because they draw power from a vast tank-free supply of ambient kinetic energy in vibrations. Unfortunately, small devices alone seldom dampen vibrations enough to fully harness what is available, which is why investing energy to increase the electrical damping force that transducers impose is so important. This paper introduces and evaluates three investment schemes and 0.35-μm CMOS switched-inductor circuits that increase this force to generate more output power.