A rectifier-free piezoelectric energy harvester circuit

Although the benefits of incorporating noninvasive intelligence (e.g. wireless micro-sensors) to state-of-the-art and difficult-to-replace technologies are undeniable, micro-scale integration constrains energy and power to the point lifetime and functionality fall below practical expectations, forcing technologists to seek energy and power from the surrounding environment. To this end, a piezoelectric energy harvester circuit is proposed. The 2 mum CMOS design circumvents the need for (and losses and low-voltage restrictions associated with) a rectifier by extracting and transferring energy directly from the piezoelectric transducer to the battery via a switched inductor. Simulation results show that the proposed system can harvest 45 nJ and 10 nJ per period at 71% and 69% efficiency from 3 V and 1.5 V peak piezoelectric voltages, respectively.