The electrical supply of portable electronic devices is a
crucial problem, which may be solved by harvesting a part of the mechanical
energy dissipated in our environment. For the last ten years, many prototype
piezoelectric generators have been proposed in research literature, offering
different technological choices, but always working according to the same
schematics: three different conversion stages. The first one, named
mechanical application device (MAD), transforms the initial mechanical
stress into a higher level or higher frequency stress. This stress is
applied to the second stage, the piezoelectric device (PD). The last stage,
an electronic circuit named harvesting system (HS), is essential to maximise
the electrical energy delivered to the targeted electronic device. In this
paper, we present an experimental test bench that can replace any
association of MAD and PD. Then we describe our HS, and demonstrate its
performances for our application, where the applied mechanical stress is
exponential and varies with a low frequency. Thanks to this HS, the
conversion from mechanical energy to electrical energy is improved, and this
phenomenon can be explained by simulation, using an equivalent circuit. At
last, some experimental results are commented, leading to the perspectives
of this research project.