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Converter
Kinds of Converter Terms modified by Converter Selected AbstractsVOLTAGE REGULATION OF A BUCK BOOST CONVERTER,A HYBRID CONTROL APPROACHASIAN JOURNAL OF CONTROL, Issue 4 2007C. Sreekumar ABSTRACT In this paper, the output voltage regulation problem in a buck boost converter is defined as a hybrid control problem. For control design, the mutually interacting continuous and discrete dynamics are modeled as a hybrid automaton. Thus, the control problem is defined as a guard selection problem of the hybrid automaton. The system trajectory is switched between different modes based on the guards to achieve the required voltage regulation. The guards defined are fixed surfaces represented in terms of the state variables for a given operating condition. The logic-based switching in the state plane is stable in terms of the chaotic and bifurcation behavior. The effectiveness of the control scheme for buck and boost operation under line and load disturbances is demonstrated by simulation in the MATLAB-SIMULINK environment and the results are presented. [source] A White LED Driver Using a Buck,Boost ConverterIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 5 2010Kei Eguchi Member Abstract For mobile backlighting applications, a white LED (WLED) driver using a buck,boost converter is proposed in this letter. Unlike conventional converters using boost converters, 2×/1.5× charge pumps, and so on, the proposed converter offers the negative stepped-down voltage to drive the LED's cathode only when the input voltage is insufficient to drive a 1× transfer mode. Furthermore, unlike the LED backlight using charge pumps, the proposed converter can adjust the output voltage by controlling the duty factor of the clock pulse. Thus, the proposed converter can realize high power efficiency. The validity of the proposed converter is confirmed by simulations and experiments. © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Sliding Mode ,-, Modulation Control of the Boost ConverterASIAN JOURNAL OF CONTROL, Issue 4 2005Hebertt Sira-Ramķrez ABSTRACT A switched implementation of average dynamic output feedback laws trough a ,-,-modulator, widely known in the classic communications and analog signal encoding literature, not only frees the sliding mode control approach from state measurements and the corresponding synthesis of sliding surfaces in the plant's state space, but it also allows to effectively transfer all desired closed loop features of an uniformly bounded, continuous, average output feedback controller design into the more restrictive discrete-valued (ON-OFF) control framework of a switched system. The proposed approach is here used for the input-output sliding mode stabilization of the "boost" DC-to-DC converter. This is achieved by means of a well known passivity based controller but any other output feedback design would have served our purposes. This emphasizes the flexibility of the proposed sliding mode control design implementation through ,-,-modulators. [source] Physical Modeling and Optimization of Bottom Tuyere Configuration and Blowing Parameters in a Top and Bottom Combined Blowing ConverterASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2006Liang-Cai Zhong Optimizing experiments for the bottom tuyere configuration and blowing parameters of the 120 tonne top and bottom combined blowing converter at Shaoguan Iron & Steel Co. were carried out in a reduced-scale water model. Results showed that the former configuration with 6 bottom tuyeres in the converter was not suitable with bath stirring because of the two tuyeres arranged in 0.33D pitch circle which caused the cavity deformation and stirring energy loss. Ideal bath stirring in the converter was obtained by using a new arrangement with 4 bottom tuyeres, two being in 0.57D pitch circle and the other two in 0.42D pitch circle. The optimal blowing parameters of the converter with the new bottom tuyere configuration were 1.26 Nm3/h of bottom gas flow rate, 160 mm of top lance height, and 30.52 Nm3/h of top gas flow rate. [source] Dynamic range expansion of receiver by using optimized gain adjustment for high-field MRICONCEPTS IN MAGNETIC RESONANCE, Issue 4 2010C.H. Oh Abstract In high-field magnetic resonance imaging (MRI) system, the signal-to-noise ratio of MR signal is so high that the receiver frequently cannot cover the full dynamic range of the MR signal. Although this problem can be overcome by using a compander (compressor and expander) composed of logarithmic amplifiers and a ROM table to retrieve the nonlinearity of the logarithmic amplifiers or by simply increasing the number of bits of analog-to-digital converter, the methods can be costly and complex or even impossible for most commercial systems. In addition, the spectrometer has to be specifically designed to operate in those modes. In this article, we developed a simple dynamic range improvement method using a receiver with optimized variable gain control in which function can be implemented without any hardware modification to the spectrometer, if the spectrometer can do gain control during a scan. Simulations as well as experiments for the brain and resolution phantom have been performed, and the results demonstrate the utility of the proposed method. © 2010 Wiley Periodicals, Inc. Concepts Magn Reson Part A 36A: 243,254, 2010. [source] A workflow portal supporting multi-language interoperation and optimizationCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 12 2007Lican Huang Abstract In this paper we present a workflow portal for Grid applications, which supports different workflow languages and workflow optimization. We present an XSLT converter that converts from one workflow language to another and enables the interoperation between different workflow languages. We discuss strategies for choosing the optimal service from several semantically equivalent Web services in a Grid application. The dynamic selection of Web services involves discovering a set of semantically equivalent services by filtering the available services based on metadata, and selecting an optimal service based on real-time data and/or historical data recorded during prior executions. Finally, we describe the framework and implementation of the workflow portal which aggregates different components of the project using Java portlets. Copyright © 2007 John Wiley & Sons, Ltd. [source] A survey of interfacial forces used during filing of root canalsDENTAL TRAUMATOLOGY, Issue 3 2000J. D. Regan Abstract , The pattern of dentine removal during endodontic instrumentation is influenced by many factors including the interfacial forces applied by the operator. The aim of this study was to investigate the influence of operators and different sizes and types of instruments on the magnitude of these interfacial forces. Single-rooted teeth were mounted on a cantilevered aluminium beam to which two pairs of single element strain gauges were joined in a half-bridge configuration and mounted at right angles to each other. The strain gauges were connected to an analogue-to-digital converter fitted in a micro-computer via conditioning amplifiers. This enabled strains to be recorded over a period of time. Twenty operators instrumented root canals using a series of hand instruments for 1 min each. The mean interfacial forces used by operators demonstrated a wide variation ranging from 9.06 g to 149.42 g (range of forces from 0,331 g) but there was a consistency in the relative magnitude for each operator. The 20 operators could be divided into 13 groups which were significantly different (,=0.05) from each other. There were significant differences (,=0.05) between the forces used for each of the K-Flex files (15, 25, 35, 45, and 70), the force increasing with the file size. There was also a significant difference (,=0.05) in the forces used between the Flexofile (#25) and the #25 K-Flex and Hedström files. However, there was no significant difference between the K-Flex and Hedström files. [source] Improvement of pulse pattern for space vector modulated matrix convertersELECTRICAL ENGINEERING IN JAPAN, Issue 1 2010Kichiro Yamamoto Abstract Novel modulation which consists of conventional space vector modulation (SVM) based on a virtual AC/DC/AC conversion and carrier signal modulation for matrix converters is proposed. In this proposed modulation, duties for the switching pattern decided by conventional SVM are changed into those for each switch of matrix converter. The new duties for each output phase are compared with the triangle carrier. By using proposed modulation, switchings between the input phase voltage with minimum value and the voltage with maximum value are eliminated. In this paper, the conventional SVM and proposed modulation are explained. Next, for both conventional and proposed modulations waveforms of input current, output voltage and output current and their frequency spectra are calculated by PSIM simulation program. Simulation results show the proposed modulation can reduce harmonics of output voltage waveforms. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(1): 46,54, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20903 [source] Experimental study of a doubly-fed rotary frequency converterELECTRICAL ENGINEERING IN JAPAN, Issue 4 2010Yasutoshi Takemoto Abstract Wind power generation using an unlimited, natural energy has been getting attention regarding environmental issues in recent years, and the installed capacity of wind power generation system is increasing at a rapid pace, resulting in deterioration of power quality especially in frequency and voltage. This fact will be a big problem in restricting large capacity of wind farms. This paper proposes a new frequency converter: rotary frequency converter (RFC) to moderate the electric output from wind generation, which is to be installed between a set of wind generators and a grid, providing a smoothed electric output, promoting the wind power generation introduction. This mainly consists of a synchronous machine and the adjustable-speed machine. Independent controls of input/output voltage, active power, and reactive power offer electrical separation between the two networks. Experimental study of a prototype model and its characteristics, especially dynamic control, is discussed in this paper. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(4): 26,34, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20922 [source] Direct-power-control-based matrix converter and its operation characteristicsELECTRICAL ENGINEERING IN JAPAN, Issue 2 2010Toshihiko Noguchi Abstract This paper proposes a novel control strategy for a matrix converter, which features direct instantaneous active- and reactive-power control of the converter. The theoretical aspects of the proposed control are discussed, and computer simulation results are presented to confirm the basic controllability of the technique. In addition, several operational characteristics were examined through experimental tests, using a 1.5-kW prototype. The maximum efficiency and the total input power factor of the prototype with a 30-Hz output frequency were 95.4% and 99.9% at 1.5-kW load, respectively. The total harmonic distortion at the rated load was 5.9%. These results demonstrate the feasibility and effectiveness of the proposed strategy. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(2): 53,59, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20886 [source] Voltage fluctuation compensator for ShinkansenELECTRICAL ENGINEERING IN JAPAN, Issue 4 2008Tetsuo Uzuka Abstract In AC electric railways, three-phase voltage is changed into the single-phase circuit of two circuits with the Scott-connected transformer. If unbalancing of the load between single-phase circuits becomes large, voltage fluctuation becomes large on the three-phase side. Railway static power conditioner (RPC) was developed for the purpose of controlling voltage fluctuation on the three-phase side. An RPC is comprised of a pair of self-commutated PWM inverters. These inverters connect the main phase and teaser feeding buses, coupled with a DC side capacitor such as a back-to-back (BTB) converter. In this way, the two self-commutated inverters can act as a static var compensator (SVC) to compensate for the reactive power and as an active power accommodator from one feeding bus to another. 20 MVA/60 kV RPCs started commercial operation in 2002 at each two substations on the newly extended Tohoku Shinkansen for compensating voltage fluctuation on the three-phase side caused by traction loads, absorbing harmonic current. The results of operational testing indicate that an RPC can accommodate single-phase loads such as those of PWM-controlled Shinkansen and thyristor phase-controlled Shinkansen, and handle the exciting rush current of transformers, as well as compensate for harmonics successfully. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(4): 25,34, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20397 [source] A Versatile System for Arbitrary Function Large-Amplitude Fourier Transformed VoltammetryELECTROANALYSIS, Issue 13 2007Lishi Wang Abstract A novel low-cost instrument for arbitrary function large-amplitude Fourier transformed voltammetry was developed. Description of both hardware and software was given in detail in this paper. A micro-control-unit (MCU) in combination with a field programmable gate array (FPGA) was designed to act as the controller of the instrument. Profiting from the built-in USB2.0 standard interface of the MCU, vast amount of data to/from the high resolution digital-to-analog converter (DAC)/analog-to-digital converter (ADC) then could be exchanged with computer in real-time, instead of being temporarily stored at the capacity limited memory of the instrument which always restricted the length of sampling time and the size of the collected data set. In the [Fe(CN)6]4+/3+ system, by superimposing a sinusoidal waveform with an amplitude of 120,mV onto a triangular potential and then applying to a macro electrode through the instrument, voltammograms up to the eighth harmonic could be well resolved by FT-IFT method. Excellent agreement was attained with Bond's similar experiment [Anal. Chem. 76 (2004) 3619] in respect of the shape and relative peak height of each harmonic. With the simply structured instrument, stable performance, flexible and versatile function was achieved. Arbitrary forms of AC perturbation which may not necessarily be sinusoidal or square-wave or other regular formed periodic signal could be synthesized and superimposed onto a DC potential as the excitation signal with this instrument. Some more useful electrode process information was expected to unveil by utilizing the FT-IFT algorithm to dissect the response signal. [source] Bit-length expansion for digital imagesELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 10 2009Tomoaki Kimura Abstract Bit-length of digital images is decided by the Analog-to-Digital (AD) converter. The bit-length expansion technique is necessary for high-quality displays such as the liquid crystal display (LCD) and the plasma display. Bit-length expansion is also necessary for low-bit length images, which are degraded by the pseudo-contour. In this paper, we propose a bit-length expansion method from M -level to N -level [N=3(M,1)+1]. This operation means that two quantization levels are introduced between existing levels. The bit-length expansion method results in the estimation problem of an error image between an M -level's image and an N -level's image. The error image is the pattern image which consists of three values. We show the estimation method of the three values pattern image and that the proposed method can remove the pseudo-contour of digital images through several application results. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(10): 32,40, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10105 [source] A high-efficiency diode-clamped linear amplifierELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 6 2008Hideaki Fujita Abstract This paper proposes a new power converter without any switching operation and which works as a linear amplifier. The main circuit of the proposed converter consists of series-connected MOSFETs, series-multi DC power supplies, and clamping diodes. The circuit configuration is similar to a diode-clamped multi-level inverter, except for using complementary power devices, which are n- and p-channel MOSFETs. One of the series-connected MOSFETs operates in an active state just like a linear amplifier, while the other MOSFETs operate in on or off states like an inverter circuit. As a result, the proposed converter achieves an acceptable efficiency as high as 90% without any ripples or harmonics caused by switching operation. Experimental results demonstrate that the proposed converter has the capability to drive a 2.2-kW three-phase induction motor. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(6): 47,56, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10120 [source] Ultrasonic treatment of waste activated sludgeENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2006Raf Dewil Abstract Activated sludge processes are key technologies to treat wastewater. These biological processes produce huge amounts of waste activated sludge (WAS), now commonly called biosolids. Mechanical, thermal, and/or chemical WAS conditioning techniques have been proposed to reduce the sludge burden. The ultrasonic treatment of WAS is quite novel. The present paper reports on extensive investigations using an ultrasonic treatment of WAS, to study its potential to meet one or all of four objectives: (1) reduce WAS quantities; (2) achieve a better dewaterability; (3) provoke a release of soluble chemical oxygen demand (COD) from the biosolids, preferably transformed into biodegradable organics; and (4) possibly destroy the filamentous microorganisms responsible for sludge bulking. Although meeting these objectives would help to solve the problems cited, the energy consumption could be a considerable drawback: the paper will thus assess whether all or some objectives are met, and at what operational cost. A literature survey defines the occurring phenomena (cavitation) and the important operation parameters [such as frequency, duration, specific energy input (SE)]. The experiments are carried out in a batch reactor of volume up to 2.3 L. The ultrasonic equipment consisted of a generator, a converter, and a sonotrode, supplied by Alpha Ultrasonics under the brand name of Telsonic. Three different kinds of sludge were tested, with different concentrations of dry solids (DS) between approximately 3.5 and 14 g DS/L WAS. Ultrasonic energy was introduced in a continuous manner (against possible pulsed operation). The major operational parameters studied include duration of the ultrasonic treatment and specific energy input. The applied frequency was set at 20 kHz. The release of COD from the WAS phase into the filtrate phase is a function of the specific energy input with yields of nearly 30% achievable at SE values of 30,000 kJ/kg DS. A major fraction of the COD is transformed into biodegradable organics (BOD). The reduction in DS fraction of the sludge is proportional to the COD release rates. Although the DS content is reduced, the dewaterability of the sludge is not improved. This reflects itself in increased filtration times during vacuum filtration and in increased values of the capillary suction time (CST). This more difficult dewaterability is the result of considerably reduced floc sizes, offering an extended surface area: more surface water is bound (CST increases) and the filterability decreases as a result of clogging of the cake. To reach the same dryness as for the untreated cake, the required dosage of polyelectrolyte is nearly doubled when the SE of the ultrasound treatment is increased from 7500 to 20,000 kJ/kg DS. The ultrasonic reduction of filamentous WAS organisms is not conclusive and very little effect is seen at low intensities and short treatment durations. Microscopic analysis of the WAS identified the dominant presence of Actynomyces. The release of soluble COD and BOD certainly merit further research. © 2006 American Institute of Chemical Engineers Environ Prog, 2006 [source] Structures and modulation algorithms of direct ac/ac converters with two legs and three legs for two-phase systemsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2010Sangshin Kwak Abstract Two-phase ac/ac matrix converter configurations are presented based on direct power conversion processes from three-phase input ac supplies to two-phase output ac loads. Two types of two-phase matrix converter topologies, utilizing the standard matrix converter configuration, are introduced with two-leg and three-leg based structures. Pulse width modulation (PWM) strategies with high-frequency composition for the two-leg and the three-leg based two-phase matrix converters are developed to synthesize sinusoidal output waveforms of two-phase loads from time-varying input ac voltages. Grounded on the developed modulation algorithms, the presented matrix converters directly generate controllable two-phase output voltages from sinusoidal input voltages with no intermediate dc conversion and concomittant dc-link elements. The proposed matrix converters can provide sinusoidal output current/voltage waveforms with independently controlled magnitude and 90° phase angle to two-phase loads. Thus, the converters are effective for both balanced and unbalanced two-phase loads. The presented two-phase operations with the standard matrix converter structures add the versatility for the matrix converter systems to function in multi-phase loads as a universal converter. Simulation and experimental results are presented to verify the developed modulation techniques and the converter configurations for the two-phase matrix converters. Copyright © 2009 John Wiley & Sons, Ltd. [source] Damping torque analysis for DC bus implemented damping control,EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2010W. Du Abstract Damping torque analysis is a well-developed technique for understanding and studying power system oscillations. This paper presents the applications of damping torque analysis for DC bus implemented damping control in power transmission networks in two examples. The first example is the investigation of damping effect of shunt voltage source converter (VSC) based flexible AC transmission systems (FACTS) voltage control, i.e. static synchronous compensator (STATCOM) voltage control. It is shown in the paper that STATCOM voltage control mainly contributes synchronous torque and hence has little effect on the damping of power system oscillations. The second example is the damping control implemented by a battery energy storage system (BESS) installed in a power system. Damping torque analysis reveals that when BESS damping control is realized by regulating exchange of active and reactive power between the BESS and power system, respectively, BESS damping control exhibits different properties. It is concluded by damping torque analysis that BESS damping control implemented by regulating active power is better with less interaction with BESS voltage control and more robust to variations of power system operating conditions. In the paper, all analytical conclusions obtained are demonstrated by simulation results of example power systems. Copyright © 2009 John Wiley & Sons, Ltd. [source] Fatigue life expenditure assessment and countermeasure for turbine blades due to harmonic excitations of slip energy recovery drivesEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 8 2009Jong-Ian Tsai Abstract The long-term effect of noncharacteristic harmonic currents arising from a slip energy recovery drive (SERD) on the fatigue life expenditure in turbine-generator blades is presented in this paper. Since the SERD converter can be rated at a fraction of a motor due to its static converter cascade with the wound-rotor and with high efficiency characteristics, still the feedwater pumps (FPs) in a few power plants are driven by such an induction motor (IM) drive. However, because the frequencies of the three main harmonic terms of the recovery currents are subsynchronous and offer a probability distribution due to the adjustable speed operation, a systematic fatigue estimation approach was devised by the author to investigate the long-term impact for the low-pressure (LP) turbine blades. From the simulation results, it was found that such a long-term harmonic excitation becomes a cause of turbine blade failure for single generator connected to the SERD system, even though the amplitude of these harmonic currents is normal. By the effect analysis of uncertainty, the countermeasure for the turbine integrity was then found. Copyright © 2008 John Wiley & Sons, Ltd. [source] Autonomous power system for island or grid-connected wind turbines in distributed generationEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 7 2008Grzegorz Iwanski Abstract Modern power generation systems for wind turbines are often based on the rotor fed slip-ring machines. Power electronics converter provides the slip power, and also the reactive power for excitation of the generator during standalone operation. This way the isolated load can be supplied even if the grid has failed. Stator voltage in an autonomous operation is controlled using vectorial phase locked loop (PLL) structure; therefore the information about mechanical speed or angular position of the rotor is eliminated from the control method. The second PLL is also used for synchronization of the generated voltage with the grid voltage. Voltages synchronization is necessary for soft connection and protection of the supplied load from the rapid change of the supply voltage phase. The grid-connected doubly fed induction generator (DFIG) can be useful after grid fault; however, the mains outage detection methods are necessary for fast disconnection after grid failures. Copyright © 2008 John Wiley & Sons, Ltd. [source] Fast analytical short-circuit current calculation of rectifier-fed auxiliary subsystemsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2003M. Kunz The course of time of a three-phase rectifier system which its alternating valve participation can be interpreted as a continuous sequence of alternating switching states. To allow a more convenient calculation, the substitutional circuit with the converter is transformed into state-space coordinates. Hereby each operational mode of the rectifier can be represented by two linear independent space-phasor component networks. In the state-space, an analytical solution for this boundary value system can be carried out. After a retransformation back into the time domain, its time functions can be derived. In contrast to other calculation methods, no assumptions or simplifications have to be made like ideal smooth DC currents. Furthermore, all states of operation of the rectifier bridge can be easily calculated, which cover DC side idle-running to DC short-circuit. [source] New control system for an ac-excited synchronous machine to achieve a wide field weakening range and a high overload capabilityEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2001J. Haag In the conventional AC-excited synchronous machine operated with mains excitation [1,2], the commutation conditions in the machine-side thyristor converter do not allow the drive to be notably overloaded. In addition operation with field weakening and full four-quadrant operation are not possible due to the principle. If on the other hand the AC-excited synchronous machine is excited by a small insulated gate bipolar transistor inverter (IGBT), then the commutation conditions in the machine-side thyristor converter can be improved with the control system presented here. Therefore a considerable overload capability and a field weakening range of 1:2 and more can be realized with the AC-excited synchronous machine. Areas of application previously excluded are thus opened up to the AC-excited synchronous machine. [source] High power factor ac/dc/ac converter with h-bridge cascade five-level pwm inverterEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 2 2001B.-R. Lin This paper presents an AC/DC/AC converter which consists of a three-phase switch-mode rectifier (SMR) and a three-phase multilevel inverter with separate isolated DC power supplies. Based on a hysteresis current control scheme in the stationary reference frame, the three-phase SMR is controlled to supply sinusoidal currents with high power factor and low current distortion. The separate DC bus voltages are provided by regulated switch-mode DC/DC converters. The series connection of H-bridge cells is adopted to provide multilevel phase voltage. The control scheme of the three-phase multilevel inverter is based on a look-up table with sine-triangular pulse-width-modulation (PWM) method. The voltage unbalance problem between the separate isolated DC bus voltages is improved by using the proposed control scheme. The proposed control algorithm of the AC/DC/AC converter is verified by simulation and experimental results. [source] A White LED Driver Using a Buck,Boost ConverterIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 5 2010Kei Eguchi Member Abstract For mobile backlighting applications, a white LED (WLED) driver using a buck,boost converter is proposed in this letter. Unlike conventional converters using boost converters, 2×/1.5× charge pumps, and so on, the proposed converter offers the negative stepped-down voltage to drive the LED's cathode only when the input voltage is insufficient to drive a 1× transfer mode. Furthermore, unlike the LED backlight using charge pumps, the proposed converter can adjust the output voltage by controlling the duty factor of the clock pulse. Thus, the proposed converter can realize high power efficiency. The validity of the proposed converter is confirmed by simulations and experiments. © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] High efficiency DC,DC converter for wide-ranging loads with gradual reverse current stopping techniqueIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 6 2008Kouhei Yamada Member Abstract A novel reverse current stopping technique for synchronous rectifiers in DC,DC converters is proposed. It is based on gradual adjustment of the ON-time of the synchronous rectifier to finally stop the reverse current. Therefore, delay to detect and stop reverse current does not cause extra reverse current, so almost perfect reverse current stopping can be achieved with small DC power consumption. An example circuit of the proposed technique was designed and included in a fixed ON-time pulse frequency modulation (PFM) control DC,DC converter. The designed converter was fabricated in the 0.35 µm CMOS process, and then its operation was verified. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Environmentally-friendly Aspects and Innovative Lightweight Traction System Technologies of the Shinkansen High-speed EMUsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 2 2008Yoshiyasu Hagiwara Member Abstract In 1964, the Tokaido Shinkansen marked the start of the world's first commercial service high-speed railway that operates at over 200 km/h. Since then, the Tokaido Shinkansen has demonstrated successful business and technological advancement. With the speeding-up of the Shinkansen, environmental matters such as noise and vibration have become critical issues. Measures taken to counter noise and vibration,such as weight reduction and aerodynamics,also effect global environmental measures to reduce energy consumption and CO2 emission. With the introduction of the Series 300, there was a system change of applying an AC drive system, and the lightweight body realized performance improvement over the earlier Series 0. The high-speed EMUs have readily taken advantage of technological innovation such as those achieved in electronics technology. In particular, an innovative AC drive system comprising a power converter with a GTO thyristor and asynchronous motors realized a high-performance and lightweight traction system for high-speed EMUs in the 1990s. Furthermore, recent innovations in electronics technology, such as low switching loss power devices and high-power permanent magnets, have improved the AC drive systems of the high-speed EMUs of the 21st century. This article starts out by introducing environmentally friendliness of the Shinkansen trains in terms of low energy consumption by means of traction system change, and then proceeds to describe the recent technological innovations that have given birth to lightweight traction systems, such as the Permanent Magnet Synchronous traction Motor (PMSM) and power converters with train-draft-cooling systems. The article concludes by summing up the environmentally friendly aspects of the Tokaido Shinkansen. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Energy-Saving Technologies for Inverter Air ConditionersIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 2 2008Kazunobu Ohyama Senior Member Abstract Almost all residential air conditioners in Japan are inverter air conditioners in which a permanent magnet synchronous motor (PMSM) is driven by a PWM inverter. The inverter technology can reduce the energy consumption to less than half that of air conditioners driven by a constant-speed induction motor (IM). This paper reviews the trends and the latest energy-efficient technologies for the motor and the power converter that achieve considerable energy saving. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Design and implementation of an interleaved soft-switching converter with output voltage doublerINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 2 2010B.-R. Lin Abstract An interleaved pulse-width modulation (PWM) converter with less power switches is presented in this paper. The buck type of active clamp circuit is used to recycle the energy stored in the leakage inductor of a transformer. The zero voltage switching (ZVS) turn-on of power switches is realized by the resonance during the transition interval of power switches. At the secondary side of transformers, two full-wave rectifiers with dual-output configuration are connected in parallel to reduce the current stresses of the secondary windings of transformers. In the proposed converter, power switches can accomplish two functions of the interleaved PWM modulation and active clamp feature at the same time. Therefore, the circuit components in the proposed converter are less than that of the conventional interleaved ZVS forward converter. The operation principle and system analysis of the proposed converter are provided in detail. Experimental results for a 280,W prototype operated at 100,kHz are provided to demonstrate the effectiveness of the proposed converter. Copyright © 2008 John Wiley & Sons, Ltd. [source] Analog circuit design by nonconvex polynomial optimization: Two design examplesINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 1 2010Siu-Hong Lui Abstract We present a framework for synthesizing low-power analog circuits through global optimization over generally nonconvex multivariate polynomial objective function and constraints. Specifically, a nonconvex optimization problem is formed, which is then efficiently solved through convex programming techniques based on linear matrix inequality (LMI) relaxation. The framework allows both polynomial inequality and equality constraints, thereby facilitating more accurate device modelings and parameter tuning. Compared to traditional nonlinear programming (NLP), the proposed methodology exhibits superior computational efficiency, and guarantees convergence to a globally optimal solution. As in other physical design tasks, circuit knowledge and insight are critical for initial problem formulation, while the nonconvex optimization machinery provides a versatile tool and systematic way to locate the optimal parameters meeting design specifications. Two circuit design examples are given, namely, a nested transconductance(Gm),capacitance compensation (NGCC) amplifier and a delta,sigma (,,) analog-to-digital converter (ADC), both of them being the key components in many electronic systems. Copyright © 2008 John Wiley & Sons, Ltd. [source] Global hybrid modeling and control of a buck converter: A novel conceptINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 9 2009Mohammad Hejri Abstract Several attempts have been made to design suitable controllers for DC,DC converters. However, these designs suffer from model inaccuracy or their inability to desirably function in both continuous and discontinuous current modes. This paper presents a novel switching scheme based on hybrid modeling to control a buck converter using mixed logical dynamical (MLD) methodologies. The proposed method is capable of globally controlling the converter in both continuous and discontinuous current modes of operation by considering all constraints in the physical plant such as maximum inductor current and capacitor voltage limits. Different loads and input voltage disturbances are simulated in MATLAB and results are presented to demonstrate the suitability of the controller. The transient and steady-state performance of the closed-loop control over a wide range of operating points shows satisfactory operation of the proposed controller. Copyright © 2008 John Wiley & Sons, Ltd. [source] Application of Filippov method for the analysis of subharmonic instability in dc,dc convertersINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 8 2009Damian Giaouris Abstract We propose a method of estimating the fast-scale stability margin of dc,dc converters based on Filippov's theory,originally developed for mechanical systems with impacts and stick-slip motion. In this method one calculates the state transition matrix over a complete clock cycle, and the eigenvalues of this matrix indicate the stability margin. Important components of this matrix are the state transition matrices across the switching events, called saltation matrices. We applied this method to estimate the stability margins of a few commonly used converter and control schemes. Finally, we show that the form of the saltation matrix suggests new control strategies to increase the stability margin, which we experimentally demonstrate using a voltage-mode-controlled buck converter. 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