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Applied Power Electronics Conference and Exposition, 1991. APEC '91. Conference Proceedings, 1991., Sixth Annual

Date 10-15 March 1991

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Displaying Results 1 - 25 of 86
  • APEC '91. Sixth Annual Applied Power Electronics Conference and Exposition. Conference Proceedings (Cat. No.91CH2992-6)

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  • Inverter topologies and control techniques for sinusoidal output power supplies

    Page(s): 81 - 87
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    The author reviews the state of the art in terms of power converter topologies and control techniques for realizing sinusoidal output systems. In terms of control strategy, the use of a variety of pulsewidth modulation (PWM) techniques have been proposed for realizing small filter size and good spectral performance. Some of the more popular techniques prevalent in industry are of potential importance and are reviewed. Alternatives for single and polyphase systems are examined. A variety of topologies are seen to be suitable, including conventional PWM inverters, soft switching resonant link inverters, and high-frequency AC link converters. Control strategies which yield output waveforms with good spectral purity, particularly in the presence of nonlinear loads, are examined. Both voltage and current regulator based controllers are seen to be viable alternatives View full abstract»

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  • An efficient full bridge PWM DC-DC converter topology using lossless snubber and simple active energy recovery network

    Page(s): 146 - 157
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    The single-phase full-bridge mode pulse-width modulated (PWM) DC-DC converter topology discussed minimizes switching losses and resulting stresses through the effective use of one DC bus inductor and two snubber capacitors. The inductor provides zero current turn-on and the capacitors are alternately connected across each switch, thus providing zero voltage turn-off. After turn-off, capacitor energy is transferred to the load through a low loss path. A simple active energy recovery network that increases the overall converter efficiency is also proposed. The authors include a complete circuit analysis and design procedure. Predicted results are verified experimentally on a 5 kW, 10 kHz laboratory prototype View full abstract»

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  • Japanese electronics manufacturing-an overview

    Page(s): 630 - 634
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    The author shares information gathered from a two-week study mission in Japan reviewing manufacturing practices and the management culture. The mission comprised sixteen executives from nine different companies. The mission focused on Deming award winning companies in Japan and their approach to TQC (total quality control), in all facets of the business View full abstract»

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  • Economic single phase to three phase converter topologies for fixed frequency output

    Page(s): 88 - 94
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    Several component-minimized circuit topologies for single-phase to three-phase conversion are proposed. The proposed topologies employ fewer semiconductors devices and generate high-quality output voltages. A suitable modification to achieve an active input current shaping feature is illustrated in detail. Analysis and simulation of the proposed schemes are carried out to show the high-performance features. Suitable guidelines for the selection of filter components and to facilitate circuit design are presented. Selected results are verified experimentally on laboratory prototype converters View full abstract»

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  • Generalized in-plane circuit averaging

    Page(s): 445 - 451
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    The authors present an unified approach to in-place circuit averaging that is applicable to resonant-type circuits as well as pulse-width-modulated (PWM) circuits. The approach allows the refinement of an averaged circuit model to obtain an arbitrary degree of accuracy. In the context of a particular circuit, an approximate averaged representation for each branch variable consists of a subset of the Fourier coefficients (index-k averages). The selection of this subset is determined by the dominant harmonic content of the circuit waveforms. For instance, in a series resonant DC-DC converter, the index-1 averages would be selected for the resonant tank variables, whereas the index-0 averages would be selected for the load side elements. In a PWM converter one would normally use the index-0 averages to obtain a low-frequency approximate model. These models can then be refined by including additional coefficients. This procedure is illustrated for a PWM up-down converter and for a DC-DC series resonant converter View full abstract»

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  • Real-time median filtering with a fast hardware sorter

    Page(s): 254 - 260
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    The authors describe a fast hardware implementation of a median filter with emphasis on possible applications to power electronics. The authors focus on the median filter as a relatively easily understood example which illustrates the potential of nonlinear filtering in power electronics. To show the power of the median filter, a review of offline results first presented by W. C. Karl et al. (1990) compares output from the median and linear filters for a common input waveform: a switch voltage transient in a flyback power converter. New offline results show the result of filtering a noisy motor tachometer signal with the median filter. Some of the problems and tradeoffs associated with several traditional median filtering architectures are outlined. The proposed architecture for a real-time median filter and the benefits of the design are discussed. Results from a prototype of the design are presented View full abstract»

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  • Conception and design of a parallel resonant converter for induction heating

    Page(s): 38 - 44
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    The authors present the concept and design of a parallel resonant converter for induction heating applications. The generators have a power range up to 200 kW. The inverter bridge, implemented with MOSFET transistors, can work to frequencies up to 200 kHz. The inverter is controlled by an automatic tracking circuit that makes certain that the resonant and inverter frequency are almost the same at every moment. The power delivered to the load is regulated by a feedback loop which controls the firing angle of the rectifier thyristors. After a description of the operative principle of the converter, the inverter control and design are outlined View full abstract»

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  • Steady state analysis of DC to DC resonant converter

    Page(s): 580 - 586
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    The authors describe the steady-state analysis of DC-to-DC resonant converters in the time domain as well as in the frequency domain. Closed-form expressions are derived in the time domain using a general method of determining the steady-state response of a linear time-invariant system with a periodic input. A comparative study is performed of the results obtained by the frequency domain and time domain methods to describe the operation of a DC-to-DC resonant converter. The analytical results obtained by this method are quite close to those from computer simulations View full abstract»

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  • Improvement of stability in current-programmed SEPIC DC/DC converters

    Page(s): 452 - 458
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    Techniques to enhance the stability of current-programmed single-ended primary inductance converters (SEPICs) are described, ranging from component selection to sensing a filtered copy of the control current. A summary is presented of a method for analyzing stability by direct calculation of the eigenvalues of an averaged time-evolution operator. The key to the method is the expression of duty ratio variation as a function of the state variables, i.e. voltages and currents in the circuit. This allows the formation of a modified matrix (as opposed to the straightforward weighted average of coefficients of differential equations) which approximates the time-evolution operator for the vector of state variables. Calculations are compared with experimental results View full abstract»

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  • 6 Switch-mode supply power factor improvement via harmonic elimination methods

    Page(s): 415 - 422
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    The authors present power factor improvement methods, for switched-mode power supplies, by using harmonics elimination. Three methods were valuated: a series connected resonant filter, a parallel connected resonant filter, and an active boost converter. The two passive filters are commercial products, and the boost converter is an in-house design using a power MOSFET as the switching device and a dedicated commercial IC for the control circuit. An off-the-shelf PC power supply along with the two passive filters and a boost converter were used as the test specimen. The experimental results show input power factor, distortion factor, crest factor, total harmonic distortion, and harmonic components. Also identified are the power system impacts of nonlinear current, the relative cost of harmonic elimination, and the motivation that may come from new power quality standards View full abstract»

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  • Magnetic current sensors for Space Station Freedom

    Page(s): 635 - 641
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    The magnetic current sensor presented was created under the guidance of the NASA Lewis Research Center and is dependable, lightweight, and stable over time and temperature. Flexible topology allows the design of a pin programmable hybrid package which contains analog and digital circuitry necessary for both bidirectional and unidirectional current sensing. Current ranges at different control points of the system are from 0 A to 10 A up to 0 A to 300 A. The lower ranges have a high peak value; for example, the 10 A current sensor may see 300 A during a fault condition. The final sensor design uses only one current transformer for measuring unidirectional and bidirectional current. The toroid transformer has a primary that is the utility power to be measured passing through the center of the core and one secondary coil of up to 4000 turns. External clocking ensures continuous operation View full abstract»

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  • High voltage DC shifted RF switch-mode power supply system design for gas lasers excitation

    Page(s): 173 - 177
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    A prototype DC-to-high-voltage DC-shifted RF switch-mode converter was designed, fabricated, and used to excite a low-power CO2 laser. A novel concept was used in designing the ferrite transformer which reduces the leakage inductance. A modified voltage multiplier design was used to produce the high-voltage DC-shifted RF. Converter performance analysis, laser efficiency measurements, and the effect of various converter output parameters on laser performance were obtained and are analyzed View full abstract»

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  • Coupled inductor boost converter with input and output ripple cancellation

    Page(s): 567 - 572
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    The authors describe the HS601 spacecraft battery discharge controller (BDC), a fully redundant 100 kHz boost converter which provides up to 2 kW at 50.5 VDC from a 32 cell battery (32-45 VDC). The converter is designed to be connected in parallel with a second unit to provide up to 4 kW to the spacecraft to the spacecraft bus during an eclipse. Because a single design must accommodate many different spacecraft configurations, the unit must operate properly over a wide range of battery voltage (24 to 48 VDC), load current, and load impedance. The HS601 achieves ultra-low output ripple voltage (<30 mvpp), low input ripple current (<10 mapp), and high efficiency (>90%) using a unique coupled inductor boost converter topology View full abstract»

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  • Magamp post regulators for symmetrical topologies with emphasis on half-bridge configuration

    Page(s): 380 - 384
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    The major differences between symmetrical topology magamps and the forward power converter magamp are discussed. In a forward power converter, a small portion of the magnetizing current of the power transformer is diverted to the secondary for reset of the magamp's saturable reactor. In symmetrical topologies, the transformer's magnetizing current is not used for reset of the saturable reactor(s). The magnetizing current shifts to the secondary where it causes a series of problems. The authors examine these problems, identify solutions, and explain why a half-bridge magamp power supply is inherently less versatile than the forward power converter View full abstract»

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  • Substrate and metallization selection for high power hybrid circuits based on thermal resistance and temperature cycling reliability

    Page(s): 347 - 354
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    Thermal resistance literature for materials systems used in high-power hybrid modules is reviewed. Based on the review, beryllia appears to be the best choice for a ceramic substrate material followed by aluminium nitride. Thick-film metallization and other copper metallization systems for beryllia substrates have been evaluated for aged adhesion and temperature cycling reliability. Results indicate that beryllia substrates with directly bonded copper metallization present the best choice of materials system to address thermal resistance and thermal aging as well as temperature cycling reliability issues in the high-power hybrid circuits View full abstract»

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  • Experimental study of the LLC-type series resonant converter

    Page(s): 31 - 37
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    Previous studies of the LLC-type series resonant converter (LLC-SRC) have shown that this converter possesses much better control characteristics and lower component stresses compared with those of the conventional SRC. The authors extend previous work on the LLC-SRC by presenting a complete set of design curves and formulating a systematic design procedure for the converter. Based on the design procedure, a 150 W, 200 kHz, multi-output prototype converter has been designed and tested to verify the theoretical work. Experimental results under various load and line conditions and comparison to their theoretical values are presented View full abstract»

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  • The world market [power supplies]

    Page(s): 19 - 21
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    The world power supply market is discussed briefly. The activities of the Lambda Group in this marketplace are discussed. The world power supply market is about $12 billion, of which some $7 billion is captive, i.e., equipment manufacturers making their own power supplies. The Lambda power supply group has some 6% of the $5 billion merchant market. The Lambda Group concentrates its resources into the industrial and commercial sectors, and supplies mainly to these markets: process control, telecommunications, data processing, factory automation, and test equipment. The markets shown have distinct trends, which are discussed View full abstract»

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  • Improved transient performance of a 3-phase controlled rectifier using predictive control

    Page(s): 247 - 253
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    A simple ride-through control strategy, referred to as open loop predictive control, is presented. First, a model is proposed for the commonly used three-phase controlled rectifier, and the corresponding circuit equations are derived, such that the transient response can be accurately predicted for a given sequence of firing angles and for given initial conditions. Next, an algorithm is presented which can be used in a simple computer program to generate the required sequence of firing angles that will bring the system from a given initial-state to the steady-state in the minimum time possible. Such firing angle sequences can be stored in ROM (read only memory) and then used by the controller of the rectifier to ride through short-term line disturbances. Simulation and experimental data are also presented View full abstract»

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  • A unity power factor multiple isolated outputs switching mode power supply using a single switch

    Page(s): 430 - 436
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    The authors present an offline switching power supply with multiple isolated outputs and unity power factor with the use of only one power processing stage, based on the DC-DC SEPIC (single ended primary inductance converter) modulated by variable hysteresis current control. The principle of operation, the theoretical analysis, the design procedure, an example, and simulation results are presented. A laboratory prototype, rated at 160 W, operating at a maximum switching frequency of 100 kHz, with isolated outputs rated at +5 V/15 A, -5 V/1 A, +12 V/6 A and -12 V/1 A, has been built given an input power factor near unity View full abstract»

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  • Modeling and simulation of a digitally controlled active rectifier for power conditioning

    Page(s): 423 - 429
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    The authors describe a single-phase active rectifier that provides an input AC current with unity displacement power factor and 3% total harmonic distortion (THD). The goal is to devise a rectifier to compensate for current harmonics and to improve the power factor of the line current. A closed-loop current control is proposed which will force the AC line current to be nearly sinusoidal and in phase with the input source voltage. Thus average DC output voltage is controlled to the desired value. Two topologies for the rectifier are investigated-a standard boost topology and a modified boost topology with the inductor moved to the AC side of the rectifier. Computer simulations that implement closed-loop control of the models are presented. Simulation programs and results are discussed View full abstract»

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  • Modeling losses and stresses of high frequency power converters using SABER

    Page(s): 285 - 292
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    To accurately predict the effects of parasitics on losses and stresses in high-frequency power converters, a SABER-based simulator has been developed. SABER is used to precisely model the large-signal behavior of the power converter and to calculate semiconductor losses and stresses. A separate program, which is linked with SABER, calculates the winding and core losses of the power transformer and the resonant and output filter inductor. This program models copper losses due to skin and proximity effects and uses measured data to calculate the core loss. The simulator is verified on a 50 W forward zero voltage switched multiresonant power converter operating at 2 MHz. The calculated efficiency and semiconductor stresses are in excellent agreement with the measured data. The simulator can be used iteratively to further enhance the accuracy of simulation View full abstract»

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  • Constant frequency controlled full-bridge LCC-type parallel resonant converter

    Page(s): 587 - 593
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    A constant-frequency controlled full-bridge LCC-type parallel resonant converter is presented. By using a proper transformation on the state variables, the converter is analyzed by means of a two-dimensional state-plane diagram, which shows that the converter possesses three operation modes. Control characteristics and component stress curves are derived for only operation mode II. It is shown that operating that converter in operation mode II provides the desirable converter gains for a wide load range. In addition, these control characteristics curves reveal that the converter possesses better load regulation when compared to those of the second order full-bridge constant frequency controlled parallel resonant converter. A design example and computer simulation results are given to confirm the analytical work View full abstract»

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  • Improved GTR's quasi-resonant DC link inverter

    Page(s): 506 - 510
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    A type of improved GTR quasiresonant DC link inverter is discussed. In the inverter, the active clamping circuit is removed and the DC link voltage can be limited to 1.1 Ed-1.2 Ed. The improved inverter still has the characteristic of being insensitive to the load. In the inverter circuit, it can be ensured in some range that the DC link voltage is zero at random, ensuring overcurrent and overvoltage protection safely and efficiently. This also raises the current utilization ratio of the power switch View full abstract»

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  • Fabrication method for a winding assembly with a large number of planar layers

    Page(s): 543 - 549
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    Z-folding of flex circuits is presented as a method to fabricate a winding assembly having a large number of conductive and insulating layers. The process starts with a flexible sheet which contains a copper laminate bonded to an insulating laminate. Conductor patterns are then etched on the laminates and are interleaved and folded to realize the winding assembly. A large number of thin, wide turns can be connected in series or in parallel automatically during the patterning and etching processes, thus eliminating external soldering or conductive vias. Equations relating winding resistance to geometrical parameters are derived for design purposes. A product of the z-folding technique is shown, which is a transformer with a primary winding and one-turn center-tapped secondary windings View full abstract»

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