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Efficient power conversion interface circuits for energy harvesting applications
Harvesting energy from the environment for powering micro-power devices have been increasing in popularity. These types of devices can be used in embedded applications or in sensor networks where battery replacement is impractical. In this dissertation, different methods of energy harvesting from the environment are explored as alternative sources of energy for devices. Some of the most popular energy extraction used in electronic devices today are radio frequency (RF) and thermal/vibrational energy extraction. This dissertation presents novel power techniques that enable some of the most efficient power conversion circuits published
to date.
New power conversion circuits to interface to a piezoelectric micro-power generator that produces electrical energy from temperature differences have been fabricated and tested. Circuit designs and measurement results are presented for a half-wave synchronous rectifier with voltage doubler, a full-wave synchronous rectifier and a passive full-wave rectifier circuit. The active rectifier based on synchronous rectification, fabricated in a 0.25-μm CMOS process, is 86% efficient with 22-μW peak output power when connected to the piezoelectric micro-power generator. This gives the highest efficiency to date for active rectification circuits at the micro-power level. The passive rectifier circuit is 66% efficient with 16-μW peak output power and requires no quiescent current to operate.
RF-powered devices are typically inductively coupled and extract their energy from the near field while operating within a few inches of the radiating source. Longer operating distances, exceeding 10 meters, are desired for a broader set of applications including distributed sensor networks. This dissertation describes an efficient method for far field power extraction from RF energy to enable long distance passively powered sensor networks.
Passive rectifier circuits are designed in the TSMC 0.25μm mixed-signal CMOS process and antennas for the system are printed on a 4-layer FR4 board. A high-Q resonator is used with a matching network to passively amplify the input voltage to the rectifier. At the circuit level, floating gate transistors are used as rectifying diodes to reduce the diode threshold loss in voltage rectification and therefore increase the rectifier efficiency. A 36-stage rectifier fabricated in a 0.25-μm CMOS process attains an efficiency of over 60% in the far field with a received power sensitivity of 5.5μW(-22.6 dBm), corresponding to an operating distance of 44 meters. The effective threshold voltage of the floating-gate diode is reduced to 36 mV. This is the highest performance for far-field RF energy conversion reported to date.
In ultra-low energy system, such as sensor networks, it is essential that power management circuitry are designed to dissipate very low quiescent power. RF energy and power management circuits are designed in a 0.18μm CMOS process. Voltage regulators are designed to operate at high input voltage and low power in a standard CMOS process. The voltage regulators can withstand input voltages up to 12 volts and dissipates from 90 nW to 1.4 μW of power. A floating-gate
programming circuit is designed with a self-wakeup timer that turns itself on about once a month. The floating-gate programming circuits dissipates about 30 nW in sleep mode and 8 μW in active mode
Integrated cmos rectifier for rf-powered wireless sensor network nodes
This article presents a review of the CMOS rectifier for radio frequency energy harvesting application. The on-chip rectifier converts the ambient low-power radio frequency signal coming to antenna to useable DC voltage that recharges energy to wireless sensor network (WSN) nodes and radiofrequency identification (RFID) tags, therefore the rectifier is the most important part of the radio frequency energy harvesting system. The impedance matching network maximizes power transfer from antenna to rectifier. The design and comparison between the simulation results of one- and multi-stage differential drive cross connected rectifier (DDCCR) at the operating frequencies of 2.44GHz, and 28GHz show the output voltage of the multi-stage rectifier doubles at each added stage and power conversion efficiency (PCE) of rectifier at 2.44GHz was higher than 28GHz. The (DDCCR) rectifier is the most efficient rectifier topology to date and is used widely for passive WSN nodes and RFID tags
Radio Frequency Energy Harvesting and Management for Wireless Sensor Networks
Radio Frequency (RF) Energy Harvesting holds a promising future for
generating a small amount of electrical power to drive partial circuits in
wirelessly communicating electronics devices. Reducing power consumption has
become a major challenge in wireless sensor networks. As a vital factor
affecting system cost and lifetime, energy consumption in wireless sensor
networks is an emerging and active research area. This chapter presents a
practical approach for RF Energy harvesting and management of the harvested and
available energy for wireless sensor networks using the Improved Energy
Efficient Ant Based Routing Algorithm (IEEABR) as our proposed algorithm. The
chapter looks at measurement of the RF power density, calculation of the
received power, storage of the harvested power, and management of the power in
wireless sensor networks. The routing uses IEEABR technique for energy
management. Practical and real-time implementations of the RF Energy using
Powercast harvesters and simulations using the energy model of our Libelium
Waspmote to verify the approach were performed. The chapter concludes with
performance analysis of the harvested energy, comparison of IEEABR and other
traditional energy management techniques, while also looking at open research
areas of energy harvesting and management for wireless sensor networks.Comment: 40 pages, 9 figures, 5 tables, Book chapte
On Spectrum Sharing Between Energy Harvesting Cognitive Radio Users and Primary Users
This paper investigates the maximum secondary throughput for a rechargeable
secondary user (SU) sharing the spectrum with a primary user (PU) plugged to a
reliable power supply. The SU maintains a finite energy queue and harvests
energy from natural resources and primary radio frequency (RF) transmissions.
We propose a power allocation policy at the PU and analyze its effect on the
throughput of both the PU and SU. Furthermore, we study the impact of the
bursty arrivals at the PU on the energy harvested by the SU from RF
transmissions. Moreover, we investigate the impact of the rate of energy
harvesting from natural resources on the SU throughput. We assume fading
channels and compute exact closed-form expressions for the energy harvested by
the SU under fading. Results reveal that the proposed power allocation policy
along with the implemented RF energy harvesting at the SU enhance the
throughput of both primary and secondary links
Max-min Fair Beamforming for SWIPT Systems with Non-linear EH Model
We study the beamforming design for multiuser systems with simultaneous
wireless information and power transfer (SWIPT). Employing a practical
non-linear energy harvesting (EH) model, the design is formulated as a
non-convex optimization problem for the maximization of the minimum harvested
power across several energy harvesting receivers. The proposed problem
formulation takes into account imperfect channel state information (CSI) and a
minimum required signal-to-interference-plus-noise ratio (SINR). The globally
optimal solution of the design problem is obtained via the semidefinite
programming (SDP) relaxation approach. Interestingly, we can show that at most
one dedicated energy beam is needed to achieve optimality. Numerical results
demonstrate that with the proposed design a significant performance gain and
improved fairness can be provided to the users compared to two baseline
schemes.Comment: Invited paper, IEEE VTC 2017, Fall, Toronto, Canad
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