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Applied Power Electronics Conference and Exposition, 1992. APEC '92. Conference Proceedings 1992., Seventh Annual

Date 23-27 Feb. 1992

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  • APEC '92. Seventh Annual Applied Power Electronics Conference and Exposition. Conference Proceedings 1992 (Cat. No.92CH3089-0)

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  • A simple and accurate method of computing average and RMS currents in a three-phase PWM inverter

    Page(s): 606 - 613
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    The design of three-phase pulse-width-modulated (PWM) inverters requires values for the average and RMS currents in the inverter in order to select the right components. A computer-aided investigation of approximate inverter current waveforms indicates that the average and RMS inverter currents are simple functions of a single factor equal to the product of the power factor and the modulation index. These functions have been expressed as per-unit equations that are useful not only for designing new inverters, but also for evaluating existing designs View full abstract»

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  • A guide to the application-oriented selection of AC/AC converter topologies

    Page(s): 571 - 578
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    A comprehensive review and a comparative evaluation of AC/AC converter topologies are presented. This provides guidelines for selecting an optimum technology for a given application. It is noted that, while hard switched and load commutated converters will continue to dominate the high power market in the foreseeable future, resonant soft switched converters are likely to make advances. New soft switched technologies, at least at the low power level, are expected to find more widespread use in OEM and high-performance market situations before expanding into industrial end-use applications. Of the resonant topologies, the clamped resonant DC link (RDCL) seems most appropriate for lower power levels, while the resonant pole technology is applicable for higher power ranges. Of the resonant link converters, the series resonant converter (SRC) is likely to remain the dominant one, especially for applications calling for its inherent bidirectionality and capability to operate into unbalanced loads. Successful matrix converter implementation still hinges on further development of the MCT View full abstract»

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  • High efficiency power factor correction using interleaving techniques

    Page(s): 557 - 568
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    A highly efficient 1.5 kW power factor correction converter for computer applications is presented. Eight boost-topology switching cells are interleaved to meet stringent EMI input ripple specifications while operating at a very low switching frequency (25 kHz per cell) to minimize switching losses. The result is a system with very high conversion efficiency (94%-97%, including input bridge, bias supply, and EMI filter losses) over the 93-264 VAC input range. Key implementation details, including discontinuous inductor current operation, a combination of linear and bang-bang control algorithms for fast dynamic load response, and extended (100 ms) power outage ride-through capability, are described View full abstract»

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  • Current-driven zero-voltage-switched resonant converter with capacitive output filter: analysis and experimental results

    Page(s): 211 - 218
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    The analysis and experimental results of a novel current-driven full-bridge zero voltage switching (CDFBZVS) DC/DC resonant power converter topology are presented. The present converter topology has a second-order tank circuit that consists of a parallel combination of a capacitor and an inductor. The converter exhibits zero voltage switching for a wide range of load conditions (from full load to open circuit). Due to the capacitive output filter, the voltage stresses in the tank circuit and the transistor switches are clamped to the output voltage. The converter is analyzed by means of a state-plane diagram from which the operational characteristics are obtained. To verify the analytical work, results from the experimental prototype are provided View full abstract»

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  • Small-signal modeling of average current-mode control

    Page(s): 747 - 755
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    A recently proposed average current-mode control is analyzed. A complete small-signal model for the control scheme is developed. The model is accurate up to half the switching frequency. By closing the current loop, a flat control-to-inductor current transfer function, up to half the switching frequency, can be achieved. This control scheme enables the converter to behave as an ideal current source. The subharmonic oscillation, as frequently reported in peak current-mode control, also exists in this control. This subharmonic oscillation can be eliminated by choosing a proper gain of the compensation network in the current loop. Model predictions are confirmed experimentally View full abstract»

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  • Present and future of distributed power systems

    Page(s): 11 - 18
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    The current stage of development of distributed power systems is presented. Various DC-bus and AC-bus distributed power system architectures are discussed. System integration issues related to paralleling and cascading of DC/DC converters are explained. Benefits and challenges of distributed power systems in various applications are summarized View full abstract»

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  • System design considerations for a high-power aerospace resonant link converter

    Page(s): 665 - 673
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    A novel variable-speed, constant-frequency (VSCF) 400 Hz aircraft generating system has been developed using an actively clamped resonant DC link converter. The design approach used to select the best configuration for the resonant converter power stage is described, including techniques for choosing power component values to meet key governing performance specifications. Interactions between the various converter components are discussed, suggesting approaches for selecting values which must meet multiple and sometimes conflicting system performance criteria. Verification is provided using a combination of simulation results and test data from a 60 kVA laboratory breadboard system View full abstract»

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  • Comparison of single-ended-parallel MRC and forward MRC

    Page(s): 203 - 210
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    The forward zero voltage switched (ZVS) multiresonant power converter (MRC) and the class-E derived single ended parallel (SEP) MRC are compared on the basis of their relative current and voltage stresses, and efficiency for 50 W on-board power applications. The comparison is performed using SABER large-signal simulations with experimental verification of the results. It is found that the forward ZVS-MRC operates with lower current and voltage stresses under full load conditions, whereas the SEP-MRC operates with lower current and voltage stresses under light load conditions. As a result, the full-load efficiency of the forward ZVS-MRC is higher than that of the SEP-MRC, but the efficiency of the SEP-MRC is less dependent on load variations View full abstract»

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  • A new high frequency, zero-voltage switched, PWM converter

    Page(s): 657 - 664
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    A high-efficiency, high-power-density converter operating at constant frequency and switching at zero voltage is presented. Zero voltage switching (ZVS) conditions are achieved over a broad input voltage and output current range. Continuous power transfer from the input to the output minimizes the output filter requirements, and, by using the integrated magnetics technique, high power density can be achieved. By employing the same configuration as classical pulse width modulation (PWM) topologies, a new family of ZVS-PWM converters can be derived. An experimental 5 V, 100 A converter was designed and built. The converter operates from an input voltage of 200 to 430 VDC, at a 400 kHz switching frequency View full abstract»

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  • 1990s revolution in power systems manufacturing

    Page(s): 160 - 166
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    A revolution is underway in electronics manufacturing involving fundamental philosophy, structure, and process redesign. The authors describe how these changes have been carried out at AT&T Microelectronics' Power Systems. Attention is given to the following aspects of this effort: quality, policy deployment, education and training, seven-step quality improvement, employee involvement, poka-yoke (in English, `mistake proofing'), and just-in-time. It is concluded that the changes have resulted in the best-ever quality, as evidenced by both internal quality assurance measurements and by direct feedback from customers. Intervals for both new product introduction and manufacturing have been dramatically reduced; 40% for new products and 50% for manufacturing. Shipping performance has improved 84%, with many focused factories routinely having 100% performance months View full abstract»

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  • Thermal simulation in power electronics

    Page(s): 780 - 784
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    A thermal simulation tool for power components for a coupling between electrical and thermal models is presented. Thermal simulation in steady-state operation (thermal resistance) and dynamic response (transient-thermal resistance) are shown and compared with experiments. This tool, using FLUX 2-D software, allows the thermal behavior of hybrid components to be studied. In steady-state operation, the simulation results are in good agreement with design data as well as with experimental results. However, the interfaces' designation (soldering joint, copper-ALN interface) must be detailed in order to improve thermal parameter values useful for software inputs. The simulations in dynamic operation seem to be in line with the experimental transient thermal results, except for the short periods of time where the difference of the two results becomes important View full abstract»

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  • A 1 kW unity-power-factor rectifier with isolation and fault protection

    Page(s): 541 - 548
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    A buck-type unity-power-factor rectifier having transformer isolation and short-circuit protection using a single gated switch is configured and experimentally tested as a 1 kW 48 V battery charger, operating from the 120 V line. Analytical results for worst-case fault current are verified, and a novel ripple feedback is shown to improve the short-circuit transient behavior. The buck rectifier demonstrated combines the advantage of normal operation down to zero output voltage with fast transient response due to its low internally stored energy. The AC-line current waveform is good, comparing favorably with conventional approaches. This rectifier appears particularly suitable for applications such as DC-motor drives, battery chargers, and electroplating and arc welding supplies View full abstract»

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  • The control of high-speed variable-reluctance generators in electric power systems

    Page(s): 121 - 125
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    The control of a direct-current electric power system that is sourced by a variable-reluctance generator (VRG) is studied. The power system includes the generator and its switching inverter, a filtering capacitor, a distribution network, and an electrical load. The network comprises a series resistor and inductor, while the load comprises a parallel resistor, capacitor, and power sink. The voltage at the load is regulated by adjusting the rotor angles at which the inverter switches. A method by which a load-voltage controller can be successfully designed for a power system sourced by a VRG is presented. The method employs averaging, global and local linearization, and model order reduction to facilitate the design. With the help of these techniques, a state full-state feedback controller with integral error action is designed. It appears that the controller works quite well. Transients caused by load changes clear quickly without significant overshoot or undershoot; there is no steady-state voltage regulation error: and the load voltage ripple is quite small. Preliminary experimental evidence confirms these expectations View full abstract»

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  • Improved characterization of two ZVS DC/DC resonant converters using a third order commutation network

    Page(s): 237 - 244
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    The DC analysis of a third-order, current-driven zero voltage switching (ZVS) power converter is summarized. Theoretical results as well as computer simulation and experimental data are presented. The third-order analysis shows that the results successfully converge to either of two second-order topologies analyzed previously. For large ratios of Lp/Ls, the converter's gain can be approximated by two second-order analyses. ZVS was also found not to be affected. Capacitor and transistor voltage stresses, however, were shown to be strongly affected by the presence of Ls. The results presented are significant in that they enable the designer to better understand and predict the third-order effects which are present in nearly all resonant power converters View full abstract»

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  • A resonant pulse gate drive for high frequency applications

    Page(s): 738 - 743
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    The analysis and implementation of a resonant pulse gate drive are discussed. The resonant gate drive is based on a simple charge pulse circuit which has conduction and logic losses. The pulse charging and discharging instances are controlled by the user, and hence this circuit is applicable to pulse width modulation (PWM) schemes as well as resonant converters. Theoretical analysis of the circuit shows its operation. Detailed equations are presented which describe the inherent losses of the circuit. Experimental results are shown to verify the operation and loss mechanisms View full abstract»

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  • Constant frequency ZVS converter with integrated magnetics

    Page(s): 709 - 716
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    The author introduces a high-frequency DC-DC converter which provides zero-voltage-switching (ZVS) and allows control of the output by pulse width modulation (PWM) at constant frequency. The topology is very tolerant to leakage inductance in the isolating transformer, and it is possible to combine the transformer and filter choke into a single integrated magnetic assembly yielding several additional benefits. The converter has been operated with ZVS to reduce losses at the switching transition, and this has allowed high-frequency operation even with high frequency and high input voltage. A control scheme has been defined whereby constant frequency operation and PWM produce a linear control to output transfer function with minimal interaction of load View full abstract»

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  • High frequency quasi-resonant buck converter on insulated metal substrate for avionics distributed power systems

    Page(s): 647 - 653
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    The authors present the design and construction of a low-cost, high-frequency, quasi-resonant buck converter whose power stage is surface mounted on an insulated metal substrate. Due to the ESR of the output capacitor, the control-to-output transfer function of the converter shows a behavior typical of a 1.5 order system. The converter delivers more than 30 W with an efficiency approaching 90% View full abstract»

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  • New offline switching regulators achieve ±1% regulation in a flux sensed converter

    Page(s): 513 - 516
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    A novel IC that addresses the problems in using flux sensing for output regulation in offline power supplies is described. The LT1103/LT1105 offline switching regulators eliminate the need for an opto isolator while providing ±1% line and load regulation in a magnetic flux-sensed power converter. Flux-sensing made practical simplifies the design of universal offline power supplies and provides greater safety and reliability as only the transformer requires IEC 950 conformance. Special circuitry built into the LT1103/LT1105 addresses the problems of primary leakage inductance spikes, nonlinear transformer behavior, and parasitic impedances which are present in a transformer coupled design and which previous control schemes have failed to address. Therefore, the LT1103/LT1105 provides a technological advantage for the user who needs well-registered DC output voltages from the AC line View full abstract»

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  • A SPICE compatible model of magamp post regulators

    Page(s): 793 - 800
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    An equivalent circuit that emulates the average functional behavior of a saturable reactor (SR) is developed and applied to simulate magnetic amplifier (magamp) post regulators. The equivalent circuit produces a voltage-coded signal which is proportional to the effective duty cycle (DON) of the regulator. The proposed approach converts the switching circuitry of the magamp post regulator to a SPICE-compatible equivalent circuit by replacing the SR and the switched inductor with their respective equivalent-circuit models. The resulting equivalent circuit of the system can then be used to simulate the large and small signal behavior of the regulator under static and dynamic conditions. The proposed approach was verified by comparing simulation results to previously reported analytical and experimental data. The two sets of independent results were found to be in excellent agreement. The authors demonstrate how the proposed model can be used to simplify the analysis and design of practical magamp post regulators View full abstract»

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  • An implementation of a rate dependent magnetics model suitable for general purpose circuit simulation

    Page(s): 339 - 344
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    An implementation of the Hodgdon rate-dependent magnetics model is described, and it is demonstrated that the model is suitable for general-purpose circuit simulation. Several simulation studies using the Saber simulator are presented to demonstrate that the model correctly represents static and dynamic B-H characteristics, rate-dependent phenomena, and correct transient pulse response. The model demonstrates most of the important characteristics of ferromagnetic hysteresis. Results of the simulation studies are shown to be in agreement with manufacturers' published data. Furthermore, observations concerning the Hodgdon model's appropriateness for high-rate applications and high-squareness-ratio core materials are discussed View full abstract»

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  • Computer-based symbolic circuit analysis and simulation

    Page(s): 772 - 779
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    A methodology is presented for symbolic generation of state-space equations. To implement the methodology, a circuit preprocessor, SSA-MAPL, has been developed to generate the symbolic modified modal equations. The symbolic state-space matrices are then derived using the symbolic algebra system Maple. These matrices are applied to efficiently analyze and simulate linear or switched-mode circuits View full abstract»

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  • The computer-aided design of variable-reluctance generators

    Page(s): 114 - 120
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    A computer-aided design system for variable-reluctance generators is described. The generators are the prime source for a direct-current electric power system. The design system employs Monte Carlo synthesis, fast approximate electromechanical analysis, and optimization based on multiattribute dominance. As an output, the design system provides a database of dominant generator designs and the corresponding performance of the power system. The operation of the design system is illustrated through the design of a generator for a 270 V, 10 kW, 10 krpm aerospace power system View full abstract»

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  • Inverter nonlinearities and discrete-time vector current control

    Page(s): 494 - 501
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    The authors study all-digital discrete-time vector current control loops containing a voltage-fed inverter in series with a permanent magnet synchronous motor. Normal operation of the typical pulse width modulating voltage fed inverter introduces nonlinear distortion into the voltage and the current waveforms of the motor. The authors consider both the causes and the attenuation of these disturbances using all-digital control. An effective, fully digital current controller is developed, and experimental results from a Motorola 68020 microprocessor-based system are presented View full abstract»

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  • An online UPS with improved input-output characteristics

    Page(s): 598 - 605
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    Standard uninterruptible power supply (UPS) systems are connected in series between the AC mains and the critical load. A phase-controlled rectifier feeds a battery-supported DC bus and an inverter supplies the load. These systems require two conversion stages. Input power factor is poor and large harmonic currents are injected into the AC mains. A topology is proposed which overcomes these drawbacks by placing the inverter-battery subsystem in shunt between the AC mains and the load. The battery is charged by the inverter DC bus. In normal operation, the AC mains feed the load directly, and the inverter supplies only a small amount of reactive power required to maintain the power factor very close to unity and to regulate the load voltage. The system has the following advantages: a near unity power factor, reduced line current harmonics and higher efficiency. The operation of the proposed topology and design considerations are analyzed, and operating characteristics are verified View full abstract»

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