Valeria Bottarel

Electronic interface for Piezoelectric Energy Scavenging System

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 5 V CMOS STMicroelectronics technology and measurements showed its effectiveness.

Active autonomous AC-DC converter for Piezoelectric Energy Scavenging Systems

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 PESS. 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. A test chip was diffused in 5 V CMOS STMicroelectronics technology. Experimental results show the effectiveness of this solution and efficiencies higher than 90% have been obtained for different load values.

A Nanocurrent Power Management IC for Multiple Heterogeneous Energy Harvesting Sources

This paper presents a fully autonomous power converter IC for energy harvesting from multiple and multitype sources, such as piezoelectric, photovoltaic, thermoelectric, and RF transducers. The converter performs an independent self-adapting input power tracking process for each source. The peak power conversion efficiency measured during single-source operation is 89.6%. With all sources enabled, the intrinsic current consumption is as low as 47.9 nA/source. A self-starting battery-less architecture has been implemented in a 0.32-μm STMicroelectronics BCD technology with a 2142 μm × 2142 μm die area. The IC only requires a single-shared inductor and an external storage capacitor for the basic working configuration. With respect to other multisource energy harvesters, this design specifically introduces a series of nanopower design techniques for extreme minimization of the intrinsic consumption during operation. The small chip size combined with the limited number of required external component, the high conversion efficiency, and the state-of-the-art intrinsic nanocurrent consumption make the IC suitable for many critical applications with very limited available power, such as wearable devices or unobtrusive wireless sensor networks.

Active self supplied AC-DC converter for piezoelectric energy scavenging systems with supply independent bias

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 0.35 mum CMOS STMicroelectronics technology.

Optimization of a piezoelectric energy harvester for environmental broadband vibrations

Energy scavenging systems (ESS) can be important, theoretically endless, sources of energy. In the future, they could recharge or even replace batteries. In this paper a design methodology is presented in order to maximize the harvested energy and the transduction efficiency of a cantilever-like piezoelectric scavenger. The role of geometrical parameters is investigated through a theoretical analysis based on an equivalent lumped-parameter circuit, while their optimum value is chosen by means of FEM simulations.

A nano-power energy harvesting IC for arrays of piezoelectric transducers

This paper describes a multi-source energy harvester IC for arrays of independent transducers, designed in a 0.32μm STMicroelectronics BCD technology, that can manage up to 5 AC-DC channels (e.g. piezoelectric transducers). The IC implements a boost converter based on synchronous electrical charge extraction. A single external inductor is time-shared among all transducers and access conflicts are handled by an arbiter circuit implemented as an asynchronous FSM. The designed converter is fully autonomous and suitable for battery-less operation. The circuit area is 4.6 mm2 and has a power consumption of 175 nW/source at 2.5 V while efficiency ranges between 70% and over than 85%.

Comparison of Two Autonomous AC-DC Converters for Piezoelectric Energy Scavenging Systems

Piezoelectric Energy Scavenging Systems (PESS) are used to convert the energy of mechanical vibrations into electrical energy exploiting the piezoelectric effect. Their output is a voltage which strongly varies in time; to obtain a suitable supply source an AC-DC conversion of the output voltage of these transducers is needed. Since the output power level of the energy transducer can be very low, the conversion should be as efficient as possible.

A 40 nA/source energy harvesting power converter for multiple and heterogeneous sources

This paper presents a fully autonomous integrated circuit for power conversion from multiple and heterogeneous energy harvesting transducers. Five input channel are dedicated to vibrational harvesting and exploiting multi-frequency operations. Additional four input channels are dedicated to manage DC sources. An independent MPPT is applied on each channel. A relevant feature of the design is the use of specific nano-power design techniques which reduce the converter quiescent consumption down to 40 nA/source and still keep energy conversion efficiency up to 82.8%. Only few external components are required: an external capacitor for energy storage, a single inductor and four capacitors for MPPT on DC sources.