Natan Krihely

Self-Contained Resonant Rectifier for Piezoelectric Sources Under Variable Mechanical Excitation

A rectification scheme is proposed for increasing the available output power of electrical generators that have a high output capacitance. The proposed rectifier could be useful in increasing the output power of piezoelectric generators (PZG) that convert mechanical vibrations into electrical power. The improvement is achieved by a resonant circuit that self commutates the voltage across the output terminals of the PZG and thereby eliminates the shunting of the output current by the output capacitor. A low-consumption circuit synchronously controls the operation of the resonant rectifier by detecting voltage transitions across the generator. The presented resonant rectifier was experimentally verified by connecting it to a PZG as well as to a PZG emulator. The results show that, under constant harmonic excitation, the proposed circuit can significantly increase the extracted power by up to 230% as compared to a conventional bridge rectifier. The feasibility of using the proposed topology as a self-powered system driven by variable excitation was investigated experimentally as well. In particular, the system was driven by two types of excitation source: amplitude modulated and frequency modulated. It was found that the proposed circuit increases the extracted power by 160% and 172% for AM and FM excitations, respectively.

Modeling and driving piezoelectric resonant blade elements

Piezoelectric resonant blade elements (PRB) are useful in applications such as light choppers, laser beam scanners, fans and others. Three methods are proposed for extracting the parameters of the PRB equivalent circuit model: two are direct methods and one is based on an iteration procedure that looks for the least square error. Drive needs for a PRB are discussed and possible drive alternatives are explored. The results of theoretical derivation for parameter extraction and drive requirements were verified against simulation and experiments.

Resonant rectifier for piezoelectric sources

A new rectification scheme is proposed for increasing the available output power of electrical generators that have a high output capacitance. The new rectifier could be useful in increasing the output power of piezoelectric generators (PZG) that convert mechanical vibrations to electrical power. The improvement is achieved by a resonant circuit that self commutates the voltage across the output terminals of the PZG and eliminating thereby the shunting of the output current by the output capacitor

New resonant rectifier for capacitive sources

A new rectification scheme is proposed for increasing the available output power of electrical generators that have a high output capacitance. The new rectifier could be useful in increasing the output power of piezoelectric generators (PZG) that convert mechanical vibrations to electrical power. The improvement is achieved by a resonant circuit that self commutates the voltage across the output terminals of the PZG, thereby eliminating the shunting of the output current by the output capacitor.

Efficiency Optimization of a Step-Down Switched Capacitor Converter for Subthreshold

In this brief, an efficient voltage scalable switched capacitor converter (SCC) for 1.1 V battery-powered digital system is presented. The SCC employs a binary resolution technique to preserve high efficiency at load voltages down to sub-200 mV while keeping the efficiency high. The proposed converter can be configured into four topologies to support subthreshold output levels of 0.18-0.6 V. The converter is designed in a standard lowpower 40-nm CMOS TSMC process. Simulation results show that the efficiency of the SCC can be improved by 10%-11% in the vicinity of VDD=200 mV as compared to one using a conventional approach. An optimization strategy for designing multi-topology SCC is presented to improve the effectiveness of the circuit and to preserve efficiency over large load voltages.

Modeling and evaluation of diode reverse recovery in discrete-transition simulators

Discrete transition simulators usually do not apply full physical models of devices and as a result, they are incapable of showing parasitic processes such as diode reverse recovery. The main objective of this study was to develop a behavioral model of diode reverse recovery that can be implemented in these simulators. The proposed model is based on the lumped charge control concept. It can be easily extracted from a simple measurement and it does not require heavy computational resources. The model was tested within the PSIM platform and was verified experimentally for various turn-off conditions. Model application is exemplified by investigating a lossless snubber of a three-phase buck-type rectifier.

Piezoelectric harvesting circuit with extended input voltage range

A high efficiency energy harvester for a piezoelectric generator (PZG) was developed and tested experimentally. The proposed circuit is based on a non linear resonant rectifier that replaces the simple and less efficient diode bridge rectifier. The two stage harvester (rectifier and converter) extends the input voltage range capability and mitigates the dependency of the harvester on PZG output voltage. The second stage of the proposed circuit includes a low loss converter that stabilizes the output voltage. The paper presents a comparison and evaluation of two interface schemes connected to a step-down converter. One is based on a simple diode rectifier front end and the other one is the proposed non linear rectifier. It is shown that in a self powered mode, under same acceleration level of 0.38g, the improved harvesting circuit can increase the extracted power by 186% as compared to a conventional bridge rectifier interface. In addition, experimental results show that the proposed circuit can sustain output voltage regulation 3.4 times longer compared to direct connection bridge topology for 1.8mA load step.

Optimization of a multi-target voltages switched capacitor converter

In this paper, an efficient voltage scalable switched capacitor converter (SCC) for 1.1V battery-powered system is presented. The SCC employs a binary resolution technique to step-down the input voltage to a range of voltages, while keeping the efficiency high. An optimization strategy for designing multi-topology SCC is presented to improve the effectiveness of the circuit and to preserve efficiency over large load voltages.

A friendly approach to increasing the frequency response of piezoelectric generators

A wide bandwidth piezoelectric generator (PZG) was constructed and tested experimentally. The PZG was characterized using chirp and wideband random excitations. The experimental results showed that by proper shaping of an attached cantilever beam it is possible to increase the number of vibration modes of the PZG and, hence, to improve the effectiveness of the energy harvesting as compared with a conventional cantilever PZG configuration. The proposed structure was designed to produce 3 vibration modes, which extend the operation around the frequencies 35Hz, 57Hz and 76Hz. As a result, the bandwidth was widened by a factor of 2.81 as compared with a conventional harvester.