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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.

A Nanopower Synchronous Charge Extractor IC for Low-Voltage Piezoelectric Energy Harvesting With Residual Charge Inversion

The paper presents a power converter for piezoelectric energy harvesting implementing a modified version of a synchronous electrical charge extraction with quiescent current as low as 160 nA. The input energy is increased of more than 200% for weak vibrations, by inverting the residual charge left on the capacitance of the transducer after each energy extraction. Moreover, a power management policy, named two-way energy storage, is introduced in order to improve significantly the efficiency of the energy harvesting system in battery-less systems during the startup phase, when the energy storage is fully depleted. The converter behaves as a buck-boost converter, and the measured peak efficiency is 85.3%. The IC has been designed in a 0.32-μm microelectronic technology from STMicroelectronics in an active area of 0.95 mm2.

A Nanocurrent Power Management IC for Low-Voltage Energy Harvesting Sources

This paper presents the nanopower design of an integrated 1-μW-to-5-mW power management circuit. The circuit integrates a boost converter with maximum power point tracking, a low drop-out voltage regulator (LDO), and a start-up circuit for battery-less activation from discharged states. The IC implements a dynamic two-way power routing policy that ensures a fast start-up from discharged states even with very large energy storage capacitors. In order to reduce the intrinsic power, asynchronous control logic was adopted. The circuit was implemented in a STMicroelectronics 0.32-μm microelectronic technology. The power conversion section and the LDO draw, respectively, stand-by currents of 121 and 414 nA in the active modes. The circuit achieves a peak conversion efficiency of 77.1% and a minimum start-up voltage of 223 mV.

A nano-power power management IC for piezoelectric energy harvesting applications

This paper describes a power management IC for piezoelectric energy harvesting which integrates an active AC-DC converter with residual charge inversion together with a smart self-supply architecture to speed up the start-up phase and increase harvesting effectiveness. Due to randomness of available power and to its typical intrinsic limitation to tens of μW the IC has been carefully designed to reduce quiescent current down to 150 nA while the efficiency is estimated to be at least 81%. Moreover this allows the system to be fully autonomous even with very low input energy. The IC has been designed in a 0.32 μm BCD technology from STMicroelectrics and its area is 4.6 mm2.

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%.

A Long-Distance RF-Powered Sensor Node with Adaptive Power Management for IoT Applications

We present a self-sustained battery-less multi-sensor platform with RF harvesting capability down to −17 dBm and implementing a standard DASH7 wireless communication interface. The node operates at distances up to 17 m from a 2 W UHF carrier. RF power transfer allows operation when common energy scavenging sources (e.g., sun, heat, etc.) are not available, while the DASH7 communication protocol makes it fully compatible with a standard IoT infrastructure. An optimized energy-harvesting module has been designed, including a rectifying antenna (rectenna) and an integrated nano-power DC/DC converter performing maximum-power-point-tracking (MPPT). A nonlinear/electromagnetic co-design procedure is adopted to design the rectenna, which is optimized to operate at ultra-low power levels. An ultra-low power microcontroller controls on-board sensors and wireless protocol, to adapt the power consumption to the available detected power by changing wake-up policies. As a result, adaptive behavior can be observed in the designed platform, to the extent that the transmission data rate is dynamically determined by RF power. Among the novel features of the system, we highlight the use of nano-power energy harvesting, the implementation of specific hardware/software wake-up policies, optimized algorithms for best sampling rate implementation, and adaptive behavior by the node based on the power received.

Actively Controlled Power Conversion Techniques for Piezoelectric Energy Harvesting Applications

The current advances in ultra-low power design let foresee great opportunities in energy harvesting platforms for self-powered systems. This paper presents two conversion schemes based on active control for harvesting energy with a higher efficiency than traditional passive approaches. A prototype has been developed and the approaches have been validated for piezoelectric energy harvesters with both measurements in realistic conditions (i.e. irregular vibrations) and mixed-signal circuital simulations. The proposed converters may increase harvested power of at least 25% and up to three times with respect to a passive rectifier. The harvested power is about 40 μW in presence of weak vibrations (aRMS = 1.18 m/s2) obtained in a train passenger car in motion with a 28 × 6 × 0.5 mm3 cantilever made of PZT-A4E with a 20 g mass attached at the free end.

A Sub-μ A Stand-By Current Synchronous Electric Charge Extractor for Piezoelectric Energy Harvesting

In the field of energy harvesting there is a growing interest in power management circuits with intrinsic sub-μ A current consumptions, in order to operate efficiently with very low levels of available power. In this context, integrated circuits proved to be a viable solution with high associated nonrecurring costs and design risks. As an alternative, this article presents a fully autonomous and battery-less circuit solution for piezoelectric energy harvesting based on discrete components in a low-cost PCB technology, which achieves a comparable performance in a 32 × 43 mm2 footprint. The power management circuit implements synchronous electric charge extraction (SECE) with a passive bootstrap circuit from fully discharged states. Circuit characterization showed that the circuit consumes less than 1μ A with a 3V output and may achieve energy conversion efficiencies of up to 85%. In addition, the circuit is specifically designed for operating with input and output voltages up to 20V, which grants a significant flexibility in the choice of transducers and energy storage capacitors.

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.