Self-supplied integrable active high-efficiency ac-dc converter for piezoelectric energy scavenging systems

In recent years a lot of studies focused on Energy-Scavenging Systems (ESS). An important motivation for these studies is the development of Portable Devices (PD) and of Wireless Sensor Networks (WSN). An ESS can be partitioned in two sections: the energy-scavenger itself and the electronic interface. The first one is the energy transducer while the second one is the electronic circuit which manages the energy. One of the most important objectives of the electronic interface is to realize the required ac-dc conversion. Since the output power level of the energy-scavenger can be very low, the conversion should be as efficient as possible. The goal of this paper is to design an active, high efficiency voltage doubler ac-dc converter for piezoelectric ESS which exclusively uses a fraction of the harvested energy to supply its active devices. The circuit was diffused in 0.35 mu m BCD6s technology. The simulation results show that it is possible to obtain a maximum efficiency of the ac-dc converter equal to 91%. Premiliminary experimental measurements were performed and the results obtained are in good agreement with simulations.