A waveform generator circuit for extra low‐frequency CMOS micro‐power applications

This paper presents a novel low‐power CMOS extra low‐frequency (ELF) waveform generator based on an operational trans‐conductance amplifier (OTA). The generator has been designed and fabricated using 2.5‐V devices available in 130‐nm IBM CMOS technology with a ±1.2‐V voltage supply. Using the same topology, two sets of device dimensions and circuit components are designed and fabricated for comparing relative performance, silicon area and power dissipation. The first design consumes 691 μW, while the second design consumes 943 μW using the same voltage supply. This low‐power performance enables the circuit to be used in many micro‐power applications. ELF oscillation is achieved for the two designs being around 3.95 Hz and 3.90 Hz, respectively, with negligible waveform distortion. The measured frequencies agree well with the simulation results. The first design is found to provide overall optimal performance compared to the second design at the expense of higher silicon area. Copyright © 2015 John Wiley & Sons, Ltd.     

Dynamic joint model of capacitive charge pumps and on‐chip photovoltaic cells for CMOS micro‐energy harvesting

On‐chip energy harvesting by means of integrated photovoltaic cells in standard CMOS technology can be successfully used to recharge or power‐up integrated circuits with the use of charge pumps for voltage boosting. In this paper, a tool to facilitate the design of such structures is proposed consisting of an accurate model of the joint dynamics of the micro‐photovoltaic cell and a capacitive DC/DC converter in the slow‐switching limit regime. The model takes into account both the top and bottom parasitic capacitances of the flying capacitors. We assume a classical model for the photodiode whose photogenerated current is extracted from device‐level simulations. The joint model is verified by circuit‐level simulations achieving high accuracy and computation time savings of up to 1700×. The joint model shows that the voltage generated by an integrated photovoltaic cell connected to a capacitive DC/DC converter is not constant even under constant illumination. This phenomenon can only be reproduced through the joint model and failing to take it into account results in an error in the estimation of the time needed by the DC/DC converter to reach a given output voltage. We also demonstrate that the maximum output voltage reached by a DC/DC converter in the slow‐switching limit regime when a photovoltaic cell is used as energy transducer depends on the switching frequency. Finally, the applicability of the model is illustrated through the optimization of time response and charge efficiency for the Dickson, Fibonacci, and exponential topologies in the case of implantable devices. Copyright © 2016 John Wiley & Sons, Ltd.     

A module‐integrated isolated solar micro‐inverter without electrolytic capacitors

This paper presents a module‐integrated isolated solar micro‐inverter. The studied grid‐tied micro‐inverters can individually extract the maximum solar power from each photovoltaic (PV) panel and transfer to the AC utility system. A harmonic suppression technique is used to reduce the DC‐bus capacitance. Electrolytic capacitors are not needed in the studied solar micro‐inverter. High conversion efficiency, high maximum power point tracking accuracy and long lifespan can be achieved. The operation principles and design considerations of the studied PV inverter are analyzed and discussed. A laboratory prototype is implemented and tested to verify its feasibility. Copyright © 2012 John Wiley & Sons, Ltd.     

Fabrication of flat micro‐gap electrodes for molecular electronics

Recently, organic molecular electronic devices such as molecular thin‐film transistors have received considerable attention as possible candidates for next‐generation electronic and optical devices. This paper reports on fabrication technologies of flat metallic electrodes on insulating substrates with a micrometer separation for high‐performance molecular device evaluation. The key technologies of fabricating planar‐type electrodes are the liftoff method by the combination of bilayer photoresist with overhang profile, electron beam evaporation of thin metal (Ti and Au) films, and SiO₂‐CMP (Chemical Mechanical Polishing) method of CVD (Chemical Vapor Deposition)‐deposited TEOS (tetraethoxysilane)–SiO₂ layer. The raggedness of the electrode/insulator interface and the electrode surface of the micro‐gap electrodes were less than 3 nm. The isolation characteristics of fabricated electrodes were on the order of 10¹³ ohms at room temperature, which is sufficient for evaluating electronic properties of organic thin‐film devices. Finally, pentacene FET (Field Effect Transistor) characteristics are discussed fabricated on the micro‐gap flat electrodes. The mobility of this FET was 0.015 cm²/Vs, which was almost on the order of the previous results. These results suggest that high‐performance organic thin‐film transistors can be realized on these advanced electrode structures. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(2): 39–46, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20152     

Evaluation of the introduction of a micro‐cogeneration system into residential houses based on monitored daily‐basis energy demand data

In order to reduce CO₂ emission from residential sectors in Japan, PEFC with high efficiency and low environmental impact is expected as one of the promising micro‐cogeneration (µCGS) systems. However, the energy demands in houses largely differ from each other and the profiles are also changed every day. Thus, when µCGS is actually introduced, it is necessary to examine the equipment capacity and operation of µCGS in each house. In this paper, the optimization model is developed in order to evaluate the µCGS based on daily‐basis demand data. Using actually monitored energy demand data in four households, the differences between using daily‐basis data and using the monthly‐average data are evaluated from viewpoints of economic and environmental performance of µCGS systems. Moreover, by adding the penalty factor to disposal heat of µCGS, it is seen that system configuration and system operation of µCGS can attain CO₂ reduction and energy conservation as well as cost reduction. ©2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(4): 20–30, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20653     

Alnico magnet‐based cost‐efficient design of a permanent magnet reluctance generator for wind energy conversion systems

In this work, a 6/4 permanent magnet reluctance generator (PMRG) with Alnico magnets is designed for small‐scale wind energy conversion systems and its performance is analyzed by finite element analysis. A simple converter topology is proposed to protect the Alnico magnets from demagnetization. Thus, NdFeB magnets, which are predominantly used in electric machines, can be directly replaced by Alnico magnets without changing the size or location. Since Alnico magnets are very cheap, the design cost can be significantly reduced without losing much from the generator performance. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Configuration of a voltage sag compensator by use of a micro‐SMES and experimental results

A voltage sag compensating using a micro‐SMES is presented. Based on previous works, we have carried out experiments for voltage sag compensation on the laboratory‐built system in order to validate the proposed minimum energy injection voltage sag compensation algorithm. To improve the compensating performance of the system, two‐degree‐of‐freedom voltage control is proposed. In this paper, the circuit configuration and feedback voltage control system of the compensator are described and the experimental results are reported. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(2): 84–92, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10267     

Materials,effects and components for tunable micro‐optics

An overview of recent activities in the area of tunable micro‐optical components is given. These include polymer‐based deformable mirrors for adaptive optics, tunable microlenses and arrays using fluids and membranes, pneumatically actuated scanning micromirrors and tunable Bragg filters and mirrors using swelling polymers. For each device, the structure, essential fabrication technology and optical characteristics, as well as a discussion of application areas are presented. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A novel induction generator system using bi‐directional PWM converter for small‐scale power applications

This paper presents a deadbeat current control structure for a bidirectional power flow pulse‐width modulation (PWM) converter connected to a stand‐alone induction generator (IG), which works with variable speed and different types of loads. Sensorless control of the IG, meaning stator voltage vector control without a mechanical shaft sensor, is considered to regulate both the IG line‐to‐line voltage and the DC‐bus voltage of the PWM converter. In the proposed system, a newly designed phase locked loop (PLL) circuit is used to determine the stator voltage vector position of the IG. A 2.2 kW laboratory prototype has been built to confirm the feasibility of the proposed method. The proposed cost‐effective IG system with a deadbeat current‐controlled PWM converter and capacitor bank requires only three sensors. Moreover, the required rating of the PWM converter becomes smaller due to the existence of the capacitor bank. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A new variable‐speed,constant‐frequency,stand‐alone power generating system

Variable‐speed and constant‐frequency power generating systems using rotor excitation of the wound‐rotor induction machines have been used for such applications as variable‐speed pump generators and flywheel energy storage systems. However, the stand‐alone generating system of this type has only been reported and has not yet been practically used. On the other hand, the stand‐alone generating systems using diesel engines have been widely used for emergency supplies of plants or isolated islands and so on. However, in these cases, synchronous generators are usually used. If the output frequency is to be kept constant, there is the need to control the speed of the engine using a high‐performance governor. Even then, the output frequency changes in the case of a sudden load change. This paper proposes a new stand‐alone power generating system. In this system, the constant‐frequency output voltage can be obtained even though rotor speed changes by several percent. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(2): 75–85, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10191     

Matching between straight‐wing nonarticulated vertical axis wind turbine and a new wind turbine generator

In the current wind turbine generation system, there are substantial problems such as the fact that the maximum power of the wind turbine cannot be obtained in the presence of fluctuating wind speed, as well as high cost and low annual net electricity production (due to mismatch between generators and wind turbines). A new wind turbine generator optimized for the wind turbine output is presented in order to solve such problems. This wind turbine generator consists of a permanent magnet generator, a reactor, and a rectifier, and uses neither a control circuit which requires standby electricity nor a PWM converter having a switching element. By selecting the most appropriate combination of a permanent magnet generator with multiple windings and a reactor connected in series with each winding, the maximum output of the wind turbine can be obtained without using a control circuit. The new wind turbine generator was directly coupled with a straight‐wing nonarticulated vertical‐axis wind turbine (SW‐VAWT), and matching of the generator with the wind turbine was examined in field tests. The test results and review confirm that the new wind turbine generator is highly matched with the wind turbine in the presence of fluctuating wind speed. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(2): 26–35, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21036     

RF transmitter using the dual‐pulse position modulation method for low‐power smart micro‐sensing chip

This paper presents a low‐power radio frequency (RF) transmitter using dual‐pulse position modulation (DPPM) for a smart micro‐sensing chip (SMSC) with sensors and large scale integrated circuit (LSI) on the same chip. The DPPM method is presented by a fixed pulse and a variable pulse within the same time frame. The distance between the fixed pulse and the variable pulse describes the amplitude of the input signal. A modulator and a ring oscillator were designed for the RF transmitter using the DPPM method. In the modulator, the pulse width modulation (PWM) signal is generated by the intersective method, and narrow pulses are extracted at the rising and falling positions of the generated PWM signal. The designed oscillator has the function of an oscillation controller. The RF transmitter was fabricated with sensors for an SMSC by complementary metal–oxide–semiconductor (CMOS) technology. The power consumption of the fabricated modulator was 4.5 mW. The power consumption of the proposed RF transmitter was measured as 7.0–7.3 mW at an input signal of 0.8–2.5 V. The RF transmitter using the DPPM method was able to reduce the power consumption by a maximum of 50.3% compared to a transmitter using the PWM method, because in the latter the dissipated power was 8.4–14.5 mW at the same input signal. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Design and implementation of a high‐efficiency bidirectional DC‐DC Converter for DC micro‐grid system applications

This paper studies the design and implementation of a non‐isolated dual‐half‐bridge bidirectional DC‐DC converter for DC micro‐grid system applications. High efficiency can be achieved under wide‐range load variations by the zero‐voltage‐switching features and an adaptive phase‐shift control method. A three‐stage charging scheme is designed to meet the fast‐charging demand and prolong the lifetime of LiFePO₄ batteries. A digital‐signal‐processing control IC is used to realize the power flow control, DC‐bus voltage regulation, and battery charging/ discharging of the studied bidirectional DC‐DC converter. Finally, a 10 kW prototype converter with Enhanced Controller Area Network communication function is built and tested for micro‐grid system applications. A light‐load efficiency over 96% and a rated‐load efficiency over 98% can be achieved. Copyright © 2013 John Wiley & Sons, Ltd.     

A TEA‐CO2 laser oscillation by an inductive energy storage pulsed‐power generator using a wire‐fuse opening switch

We have carried out experiments on TEA‐CO₂ laser oscillation using the inductive energy storage pulsed‐power generator, which has a copper wire fuse as an opening switch. Maximum laser output energy of about 1 J/pulse was obtained in the case of a fuse length of 5 cm and energy storage inductance of 8 μH. The laser output energy depends on the energy storage inductance and the parameters of the fuse. In this paper, the dependencies of laser output energy on inductance and fuse length, and a comparison between the inductive and capacitive system were described. Furthermore the laser efficiency was discussed by calculating the electron energy distribution of laser main discharge region. © 2000 Scripta Technica, Electr Eng Jpn, 132(1): 15–21, 2000     

A CCII‐based wide frequency range square waveform generator

In this paper, we propose a novel current‐mode solution suitable for the square waveform generation. The designed oscillator, which utilizes only two positive second‐generation current conveyors as active blocks, six resistors and a capacitor, is based on a current differentiation, instead of voltage integration, typical of developed solutions both in voltage‐mode and in current‐mode approaches, so avoiding circuit limitations due to the node saturation effects. The proposed circuit has been designed, as an integrated solution at transistor level, in a standard CMOS technology, with low‐voltage (± 1V) and low‐power (430µW) characteristics. Simulation results have confirmed the good circuit behaviour, also for working temperature drifts, showing good linearity in a wide oscillation frequency range, which can be independently adjusted through either capacitive (in the range pF ? µF) or resistive (in the range M Ω–G Ω) external passive components. Waiting for the chip fabrication, preliminary measurements have been performed using a laboratory breadboard employing the CCII with AD844 commercial component and sample capacitors and resistors. The experimental results have shown good agreement with both simulations and theoretical expectations. Copyright © 2011 John Wiley & Sons, Ltd.     

900 MHZ radio‐frequency identification rectifier with optimization and reusing of electro‐static discharges protections in 180 nm digital CMOS technology

Sensitivity and electro‐static discharges (ESD) protection level are crucial parameters for any Ultra High‐Frequency (UHF) power rectifier–harvester designed for radio‐frequency identification (RFID) devices. While sensitivity limits the reading range of the interrogator‐to‐tag communication link, the requirement for an adequate protection against ESD is enforced in commercial devices connected to a printed antenna. Both resistive and capacitive parasitics of the protection circuits severely affect RF performance of the device. In the paper, a rectifier for UHF RFID embedding an ESD protection for 2 kV human‐body discharge model (HBM) level is proposed. The target of a low added parasitic capacitance is achieved by adapting the protection circuit to the RFID rectifier and reusing the ESD clamp for additional functions being mandatory in a UHF RFID front end. The layout of the ESD clamp has been optimized for minimum parasitic resistance without sacrificing the protection level. Two UHF harvesters were implemented in a 180 nm digital complementary metal‐oxide semiconductor (CMOS) technology, featuring a minimum sensitivity of ?15.5 dBm with an ESD protection level of 2 kV HBM. Copyright © 2014 John Wiley & Sons, Ltd.     

Robust backstepping controller for grid‐side converter of DFIG‐based wind energy conversion systems

A robust backstepping controller with nonlinear damping is designed for the grid‐side converter (GSC) of a grid‐connected doubly fed induction generator (DFIG) in wind energy conversion systems (WECSs). The designed controller achieves the exponential ultimate boundedness of both the DC‐link voltage and GSC current errors with an arbitrarily fast decay rate and an arbitrarily small bound in the presence of both model uncertainties and time‐varying external disturbances. A desirable feature that distinguishes the proposed controller from other existing controllers is that the control input of GSC is constructed only by the static feedback of the measurable states. As a result, the control input becomes smooth and easy to implement without requiring differentiation or switching operations. The exponential boundedness and performance of the designed controller are demonstrated by simulation using a 1.5‐MW DFIG‐based WECS model built in MATLAB/SimPowerSystems and compared with a standard proportional‐integral controller. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A 5‐GHz energy‐efficient tunable pulse generator for ultra‐wideband applications using a variable attenuator for pulse shaping

A new energy‐efficient tunable pulse generator is presented in this paper using 0.13‐µm CMOS technology for short‐range high‐data‐rate 3.1–10.6 GHz ultra‐wideband applications. A ring oscillator consisting of current‐starved CMOS inverters is quickly switched on and off for the duration of the pulse, and the amplitude envelope is shaped with a variable passive CMOS attenuator. The variable passive attenuator is controlled using an impulse that is created by a low‐power glitch generator (CMOS NOR gate). The glitch generator combines the falling edge of the clock and its delayed inverse, allowing the duration of the impulse to be changed over a wide range (500–900 ps) by varying the delay between the edges. The pulses generated with this technique can provide a sharp frequency roll off with high out‐of‐band rejection to help meet the Federal Communications Commission mask. The entire circuit operates in switched mode with a low average power consumption of less than 3.8 mW at 910 MHz pulse repetition frequency or below 4.2 pJ of energy per pulse. It occupies a total area of 725 × 600 µm² including bonding pads and decoupling capacitors, and the active circuit area is only 360 × 200 µm². Copyright © 2011 John Wiley & Sons, Ltd.     

A salient‐pole synchronous generator with permanent magnets between the field poles

In this paper, a new salient‐pole synchronous generator (SG) termed the PMa‐SG is presented. In the PMa‐SG, permanent magnets (PMs) are placed between the pole shoes to reduce the magnetic saturation in the field poles. By using finite element analysis (FEA), the internal magnetic fields and basic characteristics of a 2.8‐MVA PMa‐SG are compared with those of a conventional SG of the same size, and the reduction effect of the magnetic saturation of the PMs is examined. The FEA simulations are also validated by experiments on a 2.0‐kVA prototype machine. The PMs placed between the pole shoes reduce the magnetic saturation in the pole bodies and pole tips and effectively increase the terminal voltage and output power. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(4): 58–67, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21132     

A fault location method using air‐gap fluxes of synchronous generator

This paper deals with an experimental investigation of a novel fault location method using air‐gap flux distributions of a synchronous generator connected to a power system. Air‐gap fluxes are the sum of field fluxes and armature reaction fluxes. Changes in armature current and field current at a fault contribute directly to the armature reaction fluxes and field fluxes, then resultant air‐gap fluxes. Therefore, air‐gap fluxes can be utilized to locate a fault. Wavelet analysis is applied to the induced voltages of search coils, which are wound around a stator tooth top for measurement of the air‐gap flux. It is shown that the fault type and location can be estimated based on the change in the search coil voltages measured during the fault. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(3): 20–27, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20707