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Abstract-The paper focuses on an electronic interface which can be used into Piezoelectric Energy Scavenging Systems (PESS). These systems convert the energy of mechanical vibrations into electrical energy using a piezoelectric transducer to realize a power supply for low power electronic systems. To obtain a suitable supply source an AC-DC conversion of the output signal of these transducers is needed and, since the output power level of the energy scavenger can be very low, the conversion should be as efficient as possible. This paper shows an active voltage doubler AC-DC converter for PESSs. A novel driving circuitry topology is presented; it has the advantage to be tolerant with respect to the process variations. The converter uses exclusively a fraction of the harvested energy to supply itself and a bias circuit has been designed to make the total current consumption supply independent. The simulation results show that the efficiency of the AC-DC converter can be as high as 94%. The circuit will be diffused in 0.35µm CMOS STMicroelectronics technology.

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 SensorsNetwork (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 a voltage doubler ac-dc converter and optimize it. A passive and an active solution were compared using the converter efficiency as a figure of merit.

The paper focuses on an electronic interface for systems, called Piezoelectric Energy Scavenging Systems (PESS), which convert the energy of mechanical vibrations into electrical energy using a piezoelectric transducer. The output of the transducer is a strong and irregular function of time hence, to obtain a suitable supply source, an AC-DC conversion is needed. Classical rectifiers (half/full bridge or voltage doubler) with an output storage capacitor do not fit very well, since they work as peak detectors, converting only input voltages which are higher than their output voltage. The paper shows an electronic interface which is able to efficiently harvest the energy associated to the randomic voltage waveform delivered by a piezoelectric transducer. Its working principle is based on an inductive step-up converter; an active driving circuit is used to set the phases of the converter. The energy is stored into a capacitor which is also used to supply the active elements of the step-up converter, realizing a completely autonomous energy scavenging system. For this reason the whole circuitry has been designed with a very low-power consumptions, about 700 nA. A prototype was diffused in 5V CMOS STMicroelectronics technology and measurements showed its effectiveness.