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Power Electronics, IEEE Transactions on

Issue 2 • Date Mar 1996

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Displaying Results 1 - 22 of 22
  • Design of microfabricated transformers and inductors for high-frequency power conversion

    Page(s): 228 - 238
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    Transformers and inductors fabricated with micron-scale magnetic-alloy and copper thin films are designed for high-frequency power conversion applications. Fine patterning produced by photolithography reduces eddy current losses, thus enabling very high power densities. Calculated design graphs and design examples for 10 MHz transformers are presented View full abstract»

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  • Discrete-time current control of voltage-fed three-phase PWM inverters

    Page(s): 260 - 269
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    The discrete-time current control of three-phase voltage-fed pulsewidth modulation (PWM) inverters is discussed, with emphasis on important practical aspects. The inverter feeds a balanced three-phase load of R-L impedances in series with back-EMFs. The inverter-load system is modeled by using space vectors. The practical difficulties of the predictive control method are pointed out. In particular, effects of the delayed application of the manipulated voltage caused by controller computing time are investigated. A modified control law that eliminates the undesirable effects of the computing delay is introduced. Also, prediction of current reference is utilized, which would enable operation with any reference function. An estimation and prediction procedure for the back EMF is also introduced. Steady-state errors in the load current due to these predictions are calculated for sinusoidal operation. Simulation results for the predictive control and the modified control laws are presented and discussed View full abstract»

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  • Application of harmonic balance-finite element method (HBFEM) in the design of switching power supplies

    Page(s): 347 - 355
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    Numerical modeling and analysis are effective techniques to assist in the design of high-frequency switching power supplies. Striving for high power densities and higher efficiencies has pushed the operating frequencies up, resulting in new circuit configurations and different component architecture. This paper presents a numerical method that is used to analyze magnetic systems for switching power supplies, in particular the switching resonant DC-DC converters. The method uses the harmonic balance technique combined with finite element methods and is referred to as the harmonic balance-finite element method (HBFEM). The HBFEM is used to solve various harmonic, eddy-current, hysteresis, and nonlinear problems applied to magnetic circuits used in switching power supplies. To evaluate the numerical results, comparisons are made with experimental results View full abstract»

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  • Loss minimization in scalar-controlled induction motor drives with search controllers

    Page(s): 213 - 220
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    Loss minimization in scalar-controlled induction motor drives (IMD) with search controllers (SC) is investigated. The problems arising when the input power is used as the controlled variable are described. It is proved that better results are achieved if the stator current is used as the controlled variable View full abstract»

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  • An integrated flyback converter for DC uninterruptible power supply

    Page(s): 318 - 327
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    An integrated flyback power converter performing the combined functions of uninterruptible power supply (UPS) and switch-mode power supply (SMPS) is presented. This power converter has a high voltage main power input and a low voltage backup battery input. DC output is obtained from the main input via a flyback power converter during normal operation and from the backup battery via another flyback power converter when input power fails. High conversion efficiency is achieved in normal, backup, and charging modes as there is only a single DC-DC conversion in each mode. The power converter circuit is very simple, with two switching transistors, a relay for mode switching, and a single magnetic structure only. This new design offers substantial improvement in efficiency, size, and cost over the conventional cascade of UPS and SMPS due to single voltage conversion, high frequency switching, and removal of design redundancy. The operation, design, analysis, and experimental results of the power converter are presented View full abstract»

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  • Neural network-based estimation of power electronic waveforms

    Page(s): 383 - 389
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    Artificial neural network techniques are indicating a lot of promise for application in power electronic systems. So far, these applications are mainly confined to control, identification, and diagnostic problems, but the application in estimation is fairly new. The paper explores the application of neural networks for estimation of power electronic waveforms. The distorted line current waveforms in a single-phase thyristor AC controller and a three-phase diode rectifier that feeds an inverter-machine load have been taken into consideration, and neural networks have been trained to estimate the total RMS current, fundamental RMS current, displacement factor, and power factor. The performance of the neural network-based estimators has been compared with the actual values, and excellent performance is indicated. Neural network-based estimation has the usual advantages of very fast and simultaneous response of all the outputs, noise, and fault-tolerant performance and can be easily implemented in dedicated analog or digital hardware chips, which can coexist with digital signal processor (DSP) and/or application-specific integrated circuit (ASIC) chips. The estimation techniques can be extended to more complex waveforms in power electronics View full abstract»

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  • Design considerations for low-voltage on-board DC/DC modules for next generations of data processing circuits

    Page(s): 328 - 337
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    By reducing the power supply voltage, a higher speed, lower power consumption, and higher integration density of data processing ICs can be achieved. Presently, a variety of ICs operating from 3.3 V are available. Next generations of ICs are expected to work even with lower voltages, i.e., in the 1-3 V range, to further enhance their speed-power performance. At the same time, during transients, these new generations of data ICs will present very dynamic loads with high current slew rates. As a result, they will require point-of-load power supplies in order to minimize the effects of the interconnection parasitics. These onboard power supplies will be derived from the existing voltages available in the system (usually 5 or 12 V), and will be required to have high power densities, high efficiencies, and good transient performance. This paper presents design considerations for these on-board power supplies and discusses their performance limits imposed by various circuit and system parasitics View full abstract»

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  • A high-performance single-phase rectifier with input power factor correction

    Page(s): 311 - 317
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    In this paper, a high-performance single-phase AC-to-DC rectifier with input power factor correction is proposed. The proposed approach has many advantages, including fewer semiconductor components, simplified control, and high-performance features, and satisfies IEC 555 harmonic current standards. Simulation and experimental results obtained on a laboratory prototype are discussed. A hybrid power module of the proposed approach is also shown View full abstract»

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  • Current-source parallel-resonant DC/AC inverter with transformer

    Page(s): 275 - 284
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    This paper gives the theory and experimental results for a current-source parallel-resonant inverter with a transformer used to change voltage levels and provide isolation. The analysis is performed in the frequency domain using Fourier series techniques to predict output power, efficiency, DC-to-AC voltage transfer function, and component voltage and current stresses. The inverter consists of two switches, a large choke inductor, a transformer, and a parallel-resonant circuit. The magnetizing inductance of the transformer is used as the inductance of the parallel-resonant circuit, thereby requiring one less component. Each switch consists of a MOSFET in series with a diode. The MOSFETs have their sources grounded so there is no need for a complicated gate-drive circuit. An inverter was designed and constructed. The DC input voltage was 156 V and the output voltage was a sine wave with a peak value of 224 V at an operating frequency of 50 kHz. The output power at full load was 100 W View full abstract»

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  • Forward converter regulator using controlled transformer

    Page(s): 356 - 364
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    A new control scheme is proposed for a forward power converter regulator using a controlled transformer. Pulse width modulation (PWM) control is used to reset the control core of the controlled transformer. As a result, a low-cost ferrite core can be used for the controlled transformer to achieve good regulation and high efficiency. Overall efficiency of 82-86% is achieved in a 200 kHz, 500 W, 5 V output regulator. A PWM-controlled transformer regulator is particularly suited for high-output-current and/or high-output-voltage postregulator applications View full abstract»

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  • Inverter output voltage synthesis using novel dead time compensation

    Page(s): 221 - 227
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    In this paper, a novel dead time compensation method is presented that produces inverter output voltages equal to reference voltages. An experimental result is also presented to demonstrate the validity of the proposed method. It shows that the compensation of the dead time is possible up to a sub-microsecond range. Also, the reference voltage can be used as a feedback value, which is essential for sensorless vector control and flux estimation. The method is based on space vector pulsewidth modulation (PWM) strategy and it can be carried out automatically by an inverter controller for initial setup without any extra hardware View full abstract»

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  • A generalized dynamic circuit model of magnetic cores for low- and high-frequency applications. I. Theoretical calculation of the equivalent core loss resistance

    Page(s): 246 - 250
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    This paper describes the theoretical calculation of the equivalent core loss resistance for a dynamic magnetic core loss model. The equivalent core loss resistance incorporates the effects of both the classical eddy current and anomalous losses. Derivation of a generalized nonlinear core loss resistance expression is presented. This new equivalent core loss resistance can be incorporated into a generalized dynamic magnetic core circuit model suitable for low and high frequency applications View full abstract»

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  • A comparison of two micromachined inductors (bar- and meander-type) for fully integrated boost DC/DC power converters

    Page(s): 239 - 245
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    Two micromachined integrated inductors (bar- and meander-type) are realized on a silicon wafer by using modified, IC-compatible, multilevel metallization techniques. Efforts are made to minimize both the coil resistance and the magnetic reluctance by using thick electroplated conductors, cores, and vias. In the bar-type inductor, a 25-μm thick nickel-iron permalloy magnetic core bar is wrapped with 30-μm thick multilevel copper conductor lines. For an inductor size of 4 mm×1.0 mm×110 μm thickness having 33 turns of multilevel coils, the achieved specific inductance is approximately 30 nH/mm2 at 1 MHz. In the meander-type inductor, the roles of conductor wire and magnetic core are switched, i.e., a magnetic core is wrapped around a conductor wire. This inductor size is 4 mm×1.0 mm×130 μm and consists of 30 turns of a 35-μm thick nickel-iron permalloy magnetic core around a 10-μm thick sputtered aluminum conductor lines. A specific inductance of 35 nH/mm2 is achieved at a frequency of 1 MHz. Using these two inductors, switched DC/DC boost converters are demonstrated in a hybrid fashion. The obtained maximum output voltage is approximately double an input voltage of 3 V at switching frequencies of 300 kHz and a duty cycle of 50% for both inductors, demonstrating the usefulness of these integrated planar inductors View full abstract»

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  • Single-switch 3φ PWM low harmonic rectifiers

    Page(s): 338 - 346
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    Existing 3φ AC-DC low-harmonic rectifiers are costly and require complex control schemes to minimize input current harmonics. Introduced here are two new classes of low cost 3φ AC-DC high power factor/low harmonic controlled rectifiers. These are derived from parent DC-DC converter topologies containing boost-type inputs and buck-type inputs. With a single active switch in addition to the diode bridge rectifier, the converters are capable of drawing a high-quality input current waveform naturally at nearly unity power factor. Thus, a simple 3φ AC-DC high power factor rectifier is obtained. Two algorithms are introduced in this paper for constructing a 3φ AC-DC high-quality rectifier. These algorithms depend on the simple switched-mode boost-type input converter and buck-type input converter modified by an input filter. For most known DC-DC converters which belong to these classes, there are corresponding 3φ AC-DC high power factor topologies, which use the same number of transistors and use six additional fast diodes. Analytical and simulation results are supplied to demonstrate the validity of the concept View full abstract»

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  • A generalized dynamic circuit model of magnetic cores for low- and high-frequency applications. II. Circuit model formulation and implementation

    Page(s): 251 - 259
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    This paper describes the formulation and implementation of a generalized dynamic magnetic core circuit model suitable for both low- and high-frequency applications. The behavior of magnetic cores with any arbitrary flux waveforms is modeled by a simple ladder network consisting of nonlinear inductors and resistors. The nonlinear B-H loop and the hysteresis loss are incorporated in distributed nonideal inductors and calculated by the Preisach scalar model of magnetic hysteresis. The eddy current and anomalous losses are accounted for by the generalized nonlinear equivalent resistors reported in Part I of the paper. The transmission line modeling method is employed to solve the nonlinear state equations. Numerical aspects and software implementation of the model are discussed. The generalized model has been verified by simulations and measurements at both low- and high-frequency operations View full abstract»

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  • An adaptive digital controller for a unity power factor converter

    Page(s): 374 - 382
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    This paper describes an adaptive digital controller for a unity power factor AC-DC power converter. The controller is based on a linear large-signal model of the boost power converter. A hardware design is presented and analyzed, followed by the software implementation of the control algorithm. Issues in digital control of power converters, such as quantization effects and fixed-point representation of system parameters, are examined in the context of this system. Experimental results are presented and compared with simulations View full abstract»

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  • Current-limiting thermistors for high-power applications

    Page(s): 304 - 310
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    Applications of positive-temperature-coefficient polymer thermistors as current-limiting elements in high-power systems are complicated by the nonlinear scaling of device parameters. The spatial and temporal evolution of the internal quantities temperature and electric field, and the temporal evolution of the external device property resistance, are described here as calculated according to a one-dimensional electrothermal model. Under a steeply ramping current excitation, a longitudinal heating instability compresses the electric field into the center of the material, thereby inducing dielectric failure. Insight into the design of a useful device is provided by results of calculations under three different conditions View full abstract»

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  • Single-cycle quasi-resonant converter with controlled timing of the power switches

    Page(s): 292 - 298
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    In this paper, aspects of the real operation of a single-cycle quasi-resonant power converter are analyzed and experimentally verified. In particular, electrical stresses and power losses in the complementary power switches are considered. A variable timing strategy of the switches, based on the direct measurement of the resonance period, is proposed and described. The experimental results and comparisons carried out on a laboratory prototype of the power converter are reported and discussed View full abstract»

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  • Charge control for zero-voltage-switching multiresonant converter

    Page(s): 270 - 274
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    The operation of zero-voltage-switching multi-resonant power converters (ZVSMRCs) limits the use of peak current-mode control. The charge control technique is found applicable to ZVSMRCs for improving dynamic performance. Charge control compares the total charge of the switch current to the control voltage to modulate the switching frequency. Since the charge of the switch current of the forward ZVSMRCs is proportional to the input voltage, charge control provides a fast inner loop and offers excellent transient response. Charge control also provides the possibility to achieve current sharing for ZVSMRC parallel applications View full abstract»

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  • Turn-off failures in individual and paralleled MCT's

    Page(s): 299 - 303
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    A turn-off failure mode in individual MOS-controlled thyristors (MCTs), initiated by a long gate voltage rise-time, is identified and analyzed. It is shown to be caused by turn-off current crowding in the MCT. In addition, a differential failure mode in paralleled devices is demonstrated in which the slower of the two MCTs fails to turn off. This is caused by the increase in anode current through the slower device and the decrease in gate voltage rise-time due to the MCTs Miller capacitance View full abstract»

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  • Applying distributed power modules in telecom systems

    Page(s): 365 - 373
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    The design of modern decentralized power systems in telecommunication applications are increasingly realized by using distributed DC/DC power modules. Power modules are usually characterized by high switching frequencies, which enable the use of small ferrite magnetics and ceramic capacitors to enhance the reliability, the power density, and the possibility of live insertion, all desired features in new power system designs. However, to utilize the advantages of power modules there are a number of considerations to be made in the design. These considerations are addressed focusing on telecom systems with an average power dissipation of <10 W/board, in free convection, i.e., nonforced convection, and <80 W/board, in forced convection cooled cabinets of commonly used mechanical sizes and designs for telecommunication equipment View full abstract»

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  • Energy based closed form solution of ZCS multiresonant series-parallel converters

    Page(s): 285 - 291
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    Under-resonant operation of an ideal multi-resonant series-parallel power converter (MRSPC) with a capacitive output filter is modeled in this paper. This operation allows zero current switching (ZCS), which is convenient for bipolar devices. The capacitive output filtering reduces the recovery effect of the rectifier diodes and is suitable for high output voltage applications. A closed-form solution is found for this power converter, based on state space analysis using energy concepts. This approach simplifies the mathematical operations and gives better physical insight of the system variables. Based on the model, the steady-state characteristics of this power converter are derived by a simulation program, which are discussed and compared with the series resonant half-bridge power converter (SRHC). The optimum power converter parameters are found for given design requirements using computerized optimization routines. Several design examples are presented and compared with SRHC. The validity of the model is verified by SPICE simulations View full abstract»

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Aims & Scope

IEEE Transactions on Power Electronics covers fundamental technologies used in the control and conversion of electric power.

Full Aims & Scope