Piezoelectric energy harvester impedance matching using a piezoelectric transformer

Abstract

To harvest maximum power from a piezoelectric energy harvester requires conjugate impedance matching, consisting of both resistive and inductive load. In practical circuits, dc-dc converters working in discontinuous conduction mode are used for emulated resistive impedance matching. These converters contain a large and expensive electromagnetic component to reduce the wire conduction losses. A new approach toward piezoelectric energy harvester resistive impedance matching is presented by using a step-down piezoelectric transformer with a bi-directional inductor-less half-bridge circuit working under zero voltage switching conditions. The large and expensive magnetic transformer and inductor in previous works are replaced with a ceramic component with no electromagnetic interference. The presented technique can reduce the circuit size and the ceramic transformer can be manufactured on the harvester cantilever.