Power density improvement of a piezoelectric energy harvester through use of a micropower switch-mode interface

Improving the power density of energy harvesters is critical to increasing functionality of self-powered miniature sensors. The power density of piezoelectric based harvesters can be greatly improved if charge modification techniques, brought about through the operation of switch-mode interface circuits, are used. Single supply pre-biasing (SSPB) has be shown to theoretically outperform all other piezoelectric harvesting interface circuits. This paper presents an experimentally verified implementation of the SSPB circuit which achieved 59% (3.6 mW) of its theoretical maximum useful output power. Use of an FPGA for timing and control allowed a control power overhead of 126 μW to be achieved. Our practical SSPB implementation achieves 14% more useful power output over the theoretical maximum achievable with synchronous switched harvester on inductor (SSHI), the second best technique.