Implementation of a Single Supply Pre-biasing Circuit for Piezoelectric Energy Harvesters

Abstract

Abstract Increased output power can be obtained from piezoelectric energy harvesters by using switching circuits that modify the charge on the material at the extremes of cantilever travel. Here we present an implementation of the most efficient of these charge modification techniques, single-supply piezoelectric pre-biasing. We describe practical results from this scheme and circuit details, including power processing components and control circuits. The power circuit current paths are synchronously commutated with MOSFETs, removing inefficient diode voltage drops. The control circuit is implemented using low power discretes. A useful output power of 2.6 mW was achieved after a 400 μW reduction required for the control circuitry. This is a factor of 4.3 greater than when the harvester was connected to a passive diode bridge and is greater than can be achieved by other piezoelectric interface circuits using an inductor with the same Q-factor.