Showing papers on "Converters published in 1988"
01 Apr 1988
TL;DR: In this paper, the half-bridge series-resonant, parallel-reonant and combination series-parallel resonant converters are compared for low-output-voltage power supply applications.
Abstract: The half-bridge series-resonant, parallel-resonant, and combination series-parallel resonant converters are compared for use in low-output-voltage power supply applications. It is shown that the combination series-parallel converter, which takes on the desirable characteristics of the pure series and the pure parallel converter, avoids the main disadvantages of each of them. Analyses and breadboard results show that the combination converter can run over a large input voltage range and a large load range (no load to full load) while maintaining excellent efficiency. A useful analysis technique based on classical AC complex analysis is introduced. >
1,795 citations
01 Apr 1988
TL;DR: In this article, a host of new quasi-resonant converters (QRCs) are derived from conventional PWM converters, with a significant improvement in performance and power density.
Abstract: Resonant switch topologies operating under the principle of zero-current switching (ZCS) and zero-voltage switching (ZVS) are introduced to minimize switching losses, stresses, and noises. Using the resonant switch concept, a host of new quasi-resonant converters (QRCs) are derived from conventional PWM converters. They are capable of operating in the megahertz range, with a significant improvement in performance and power density. Performances of ZCS and ZVS QRCs are compared. Power stages, gate drives, and feedback controls are discussed. >
369 citations
TL;DR: A critical evaluation of the aforementioned PWM techniques on the basis of application is provided, thereby giving the framework and guidelines for the selection of the best technique for each area of application.
Abstract: With the introduction and wide acceptance of gate-turnoff power drives, e.g., bipolars, power FETs, GTOs, the switching behaviour of converters has reached the point where further improvements in firing and switching networks bring out only marginal benefits. Consequently, the research interests in the area of static converters have been shifting toward improving the process of power conversion through a combination of novel circuit topologies and improved voltage and harmonic control PWM (pulsewidth modulation) techniques. As a result, several such techniques have been proposed lately. Although these techniques are clearly superior to the original sine PWM technique, little or conflicting data is available about their merits relative to each other. A critical evaluation of the aforementioned PWM techniques on the basis of application is provided, thereby giving the framework and guidelines for the selection of the best technique for each area of application. >
362 citations
01 Apr 1988
TL;DR: In this paper, the state-space averaging method associated with power converters is discussed, and the motivation and objectives of modeling by equivalent circuits based on the physical interpretation of state space averaging are discussed.
Abstract: The state-space averaging method, associated with power converters, is discussed, Emphasis is on the motivation and objectives of modeling by equivalent circuits based on physical interpretation of state-space averaging. The discussion is limited to pulse-width-modulated DC-to-DC converters. >
296 citations
TL;DR: In this article, a class of converters with zero-voltage or zero-current switching characteristics is analyzed using a method originally developed for quasiresonant and PWM (pulsewidth-modulated) converters.
Abstract: A class of converters with zero-voltage or zero-current switching characteristics is analyzed using a method originally developed for quasiresonant and PWM (pulsewidth-modulated) converters. The method relies on identifying simple three-terminal structures, called converter sections, that contain the switches and the resonant tank elements. The various zero-voltage-switched and zero-current-switched converters are obtained by permutation of these converter sections between source and sink. The method unifies the analysis of this class of converters in a single equivalent circuit model. The voltage and current waveforms in these converters are essentially squarelike except during the turn-on and turn-off switching intervals. >
220 citations
11 Apr 1988
TL;DR: In this article, the maximum input-output transformer ratio, or output voltage ability, of direct AC-AC PWM converters is explored, and an intrinsic limit, independent of the control algorithm, is found.
Abstract: The maximum input-output transformer ratio, or output voltage ability, of direct AC-AC PWM converters is explored. An intrinsic limit, independent of the control algorithm, is found. A novel converter control algorithm is discussed that achieves the maximum output amplitude and displays some interesting features. The implementation of AC-AC converter control using feedback techniques is considered, and a feedback-based control algorithm is proposed. >
179 citations
02 Oct 1988
TL;DR: In this article, an active power filter using quad-series voltage source pulsewidth modulated (PWM) converters is presented, where instantaneous space vectors of voltage and current are used for the analysis.
Abstract: The modeling, analysis, and design of an active power filter using quad-series voltage source pulsewidth modulated (PWM) converters are presented. Some instantaneous space vectors of voltage and current are used for the analysis. A vector differential equation derived in this paper makes it easy to achieve the analysis and design of the active power filter. Experimental waveforms obtained from a prototype active power filter with a rating of 7 kVA, along with simulation waveforms, are included to verify the theory presented. >
175 citations
11 Apr 1988
TL;DR: In this paper, it was shown that the PWM switch represents a static nonlinearity for which circuit models can be easily derived for frequencies harmonically related to the frequency of perturbation.
Abstract: It is shown that nonlinearity due to the switching action in pulse width-modulated (PWM) DC-to-DC converters, DC-to-AC inverters or amplifiers, and input-current-shaping DC-to-DC converters can often conveniently be confined to a three-terminal structure referred to as the PWM switch. the PWM switch represents a static nonlinearity for which circuit models can easily be derived for frequencies harmonically related to the frequency of perturbation. Converter analysis can now be approached in an analogous way to ordinary transistor circuit analysis whereby the nonlinear three-terminal device is replaced by its circuit model. A first-order approximation of the model results in the small-signal model. >
156 citations
02 Oct 1988
TL;DR: In this paper, a three-phase switch-mode rectifier (SMR) topology is proposed to reduce the component stresses in higher-10kW applications. But the authors also present an analysis and design approach for three phase SMR converters under large input voltage and load variations.
Abstract: Single-phase offline switch mode rectifiers (or offline DC-DC converters) face severe component stresses in higher than 10kW applications. The authors show that in three-phase, switch-mode rectifier (SMR) topologies' component stresses are reduced, and performance is improved substantially. These improvements include faster response times, reduced switching stresses of the power semiconductor devices, and reduced size and ratings of associated reactive components. The authors also present an analysis and design approach for three-phase SMR converters under large-input voltage and load variations. Output voltage control is achieved by varying the duty cycle of the inverter power semiconductor switches. Theoretical results are verified experimentally. >
154 citations
TL;DR: In this article, a new family of resonant converters that are regulated at a fixed switching frequency is proposed, and a steady-state analysis of the Class E resonant converter regulated by a switch-controlled capacitor is presented.
Abstract: A resonant frequency-modulation method is presented as an alternative to the switching frequency-modulation method to regulate resonant converters. A switch-controlled inductor and switch-controlled capacitor, in which switching losses are found to be very low due to zero-current or zero-voltage switching, are developed to do so. A new family of resonant converters that are regulated at a fixed switching frequency is proposed. A steady-state analysis of the Class E resonant converter regulated by a switch-controlled capacitor is presented. Theoretical and experimental results verify the validity of the proposed method. The efficiency measured from a breadboard of 1 MHz, 5 V, 25 W Class E regulated resonant DC-DC converter is up to 83%. >
138 citations
01 Apr 1988
TL;DR: The technical challenges of developing very high-power-density power supplies operating of switching frequencies in the vicinity of 10 MHz are considered in this article, where it is shown that successful development requires simultaneous considerations of topologies, materials, devices, control, electromagnetic interference, manufacturing, and packaging.
Abstract: The technical challenges of developing very-high-power-density power supplies operating of switching frequencies in the vicinity of 10 MHz are considered Primary applications are in the computer, telecommunications, and automotive industries It is shown that a successful development requires simultaneous considerations of topologies, materials, devices, control, electromagnetic interference, manufacturing, and packaging Some results of work being done at MIT are presented, including a new integrated power MOSFET/driver, high-field frequency magnetic material characterizations, and high-frequency synchronous rectifiers The design and performance of a 50-W 35-MHz converter is described >
01 Jan 1988
TL;DR: In this article, two clamped-mode resonant converters are proposed which operate at a constant frequency while retaining the desired features of conventional series-and parallel-resonant convergers.
Abstract: Two clamped-mode resonant converters are proposed which operate at a constant frequency while retaining the desired features of conventional series- and parallel-resonant converters. State-plane analyses are performed which identify all possible circuit-operating modes of a clamped-mode series-resonant converter and define their mode boundaries. The control-to-output characteristics are derived to specify design regions for both natural and forced commutations. A breadboarded circuit was built to demonstrate the feasibility of the constant-frequency clamped-mode operation. All the predicted operating modes were verified experimentally. >
TL;DR: In this article, a method is presented by which generation and classification of pulsewidth-modulated (PWM) DC-to-DC converters can be effected and a classification of basic converters is proposed in terms of converter-cell generated families.
Abstract: A method is presented by which generation and classification of pulsewidth-modulated (PWM) DC-to-DC converters can be effected. Fundamental blocks known as converter cells can be used to generate a plethora of converters leading to a number of useful new converter topologies. A classification of basic converters is proposed in terms of converter-cell generated families. >
11 Apr 1988
TL;DR: In this article, a modeling and synthesis technique for single-ended, ladder-structured, DC-DC converter topologies is introduced for topological constraints that enhance the understanding of structural properties of converter circuits and clarify the roles of inductors and capacitors in various converters.
Abstract: A modeling and synthesis technique is introduced for single-ended, ladder-structured, DC-DC converter topologies. Topological constraints are derived that enhance the understanding of structural properties of converter circuits and clarify the roles of inductors and capacitors in various converters using magnetic or capacitive energy storage/transfer mechanism. The exact duality relationships among the basic converter topologies are established. >
TL;DR: An alternative set of parameters for characterizing the linear, nonlinear, and statistical properties of analog-to-digital (A/D) converters is suggested, and an algorithm, referred to as the sinusoidal minimum error method is proposed to estimate the values of these parameters.
Abstract: Quantities such as peak error and integral or differential nonlinearity are commonly used to characterize the performance of analog-to-digital converters. However, these measures are not readily applicable to converter architectures that use feedback and oversampling. An alternative set of parameters for characterizing the linear, nonlinear, and statistical properties of analog-to-digital (A/D) converters is suggested, and an algorithm, referred to as the sinusoidal minimum error method is proposed to estimate the values of these parameters. The suggested approach is equally suited to examining the performance of A/D converters by means or either computer simulations of experimental measurements on actual circuits. >
TL;DR: In this paper, a three-phase AC-DC converter is analyzed and the performance of the converter under balanced conditions is evaluated, and it has been observed that the level of unbalance plays a significant part in the converter characteristics.
Abstract: A three-phase AC-DC converter is analyzed, and the performance of the converter under balanced conditions is evaluated. It has been observed that the level of unbalance plays a significant part in the converter characteristics, especially at the lower output voltage range. >
30 Oct 1988
TL;DR: In this article, the authors derived switched-capacitor (SC) DC-DC converters are derived from three basic switchedcapacitors: buck, boost, and buck-boost converters.
Abstract: Novel switched-capacitor (SC) DC-DC converters are derived from three basic SC DC-DC converters. The converter outputs can be regulated by changing the duty ratio of the transistor switch. These converters have features not found in conventional switching regulators (buck, boost, and buck-boost converters). Of these converters, the voltage polarity inverting converter is expected to be widely used for small-size, small-power units because it has the following features: (1) nonpulsating input current; (2) overcurrent protection can be added; and (3) multistage connection of output circuits enables the converter to be used as a step-up, step-down converter. >
11 Apr 1988
TL;DR: In this article, the authors present a new method for calculating switching time from an accurate and explicit form of the switching condition, hence the step-by-step search for the switching instant can be greatly simplified.
Abstract: Fast long-term dynamic simulation of power converters is discussed. Because of switching actions, the converter can operate in different configurations and, therefore, it can be represented by a state-space time-varying linear system. This paper presents a new method for calculating switching time from an accurate and explicit form of the switching condition, hence the step-by-step search of the switching instant can be greatly simplified. In the proposed algorithm, a converter is partitioned into subsystems, which are simulated in a decoupled manner and coordinated through data exchange. >
TL;DR: In this article, a method of decreasing the ripple on the output voltage of high-power AC-DC or DC-DC series-resonant converters without increasing the internal converter frequency or the capacity of the energy storage elements is discussed.
Abstract: A method of decreasing the ripple on the output voltage of high-power AC-DC or DC-DC series-resonant converters without increasing the internal converter frequency or the capacity of the energy storage elements is discussed. This improvement is accomplished by subdividing the converter into two or more series-resonant power modules operated with a constant relative phase shift (phase-staggering control). The method of eliminating the harmonic components in the input and output currents of the conversion system, without increasing the internal pulse frequency, is justified by Fourier analysis of the current waveforms. The frequency spectra of the source and output waveforms for the continuous and discontinuous resonant current mode are shifted to higher frequency ranges, as computations show for both one single module and multiple paralleled modules. Inadequacies in the phase-staggering control method applied to series-resonant converters are indicated in relation to the dominant harmonic component, in particular for two modules and supported by experimentally acquired waveforms. High-frequency current components to the source and to the load are reduced. Resulting in smaller input and output filters. This improves the resolution of the control of the flow of energy from the source to the load, resulting in a faster system response. >
TL;DR: In this article, general relationships are established among variable structure control strategies and pulsewidth modulated control schemes leading to sliding modes in non-linear systems, and the results are applied to the design of a sliding regime for the regulation of DC-to-DC switchmode power converters exhibiting a slow integral manifold due to time-scale separation properties among input and output circuits.
Abstract: In this article, general relationships are established among variable structure control strategies and pulse-width modulated control schemes leading to sliding modes in non-linear systems. The results are applied to the design of a sliding regime for the regulation of DC-to-DC switchmode power converters exhibiting a slow integral manifold due to time-scale separation properties among input and output circuits.
02 Oct 1988
TL;DR: In this article, a buck/boost converter with an equivalent inductor is proposed for the operation of SRCs with boost and buck-boost characteristics, which can be designed to be controlled with advanced closed-loop feedback.
Abstract: Quantum series resonant converters (SRCs), a subset of SRCs operating on optimal conditions, are modeled. It is shown that this type of SRC can be modeled as a buck/boost converter with an equivalent inductor. Operation of SRCs with boost and buck-boost characteristics is proposed. Modeling of these converters is verified through analysis and simulation results. Using these models, the quantum SRCs can be designed to be controlled with advanced closed-loop feedback, with advantages such as low device switching stress, reliable high-frequency operation, and low EMI (electromagnetic interference). >
01 Jan 1988
TL;DR: In this article, a low-frequency dynamic model of a single-phase ac-dc power conversion system is presented, where the conversion ratio of a quasi-resonant dc-dc converter is derived in terms of the well-known PWM topology.
Abstract: Part I: Quasi-resonant converters are a family of single-switch resonant dc-dc converters featuring zero-current or zero-voltage switching. Recognition of the topological structure uniting these resonant converters--and the rectangular-wave (PWM) converters on which they are based--leads to general models of their dc and low-frequency ac behavior. An expression is derived that yields the dc conversion ratio of a quasi-resonant converter in terms of the well-known conversion ratio of the underlying PWM topology. A small-signal, low-frequency dynamic model is developed whose parameters also incorporate the PWM conversion ratio. The dc and ac models reveal that any quasi-resonant converter with a full-wave resonant switch has dc and low-frequency behavior identical to that of its PWM parent, with switching-frequency control replacing duty-ratio control. Converters with half-wave resonant switches behave more like PWM converters in discontinuous conduction mode or with current programming, exhibiting lossless damping in the small-signal model and output resistance at dc. Although quasi-resonant converters come in an astounding variety of topologies, the dc (and to a large extent ac) behavior of these converters depends only on the underlying PWM topology and the class of resonant switch, and is unchanged by movement of the resonant reactances to various alternative positions. Part 2: The distorted input-current waveforms of nonlinear electronic loads cause interference and lead to poor utilization of the utility power line, a situation that is rapidly becoming intolerable with the increased application of electronic loads. Input-current shaping, also known as power-factor improvement, addresses the problem of improving current waveforms drawn from the power line. This study is restricted to single-phase ac-dc power conversion systems. Current-shaping circuits are shown to fall into just a few categories with common features and limitations. In addition to the more common buck- and boost-based current-shaping converters, a class of circuits with "automatic" current shaping is presented and analyzed. A set of rules is derived for determining whether a particular dc-dc converter topology is suitable for use as a current-shaping ac-dc converter, and the rules are used to judge the suitability of several resonant converter topologies for this application. A new, low-cost converter is suggested that combines input-current shaping, isolation, and fast output-voltage regulation. Input-current shaping requires that a converter store significant energy, leading to unfortunate size and weight restrictions. Additional implications of stored energy are examined, along with several methods of reducing the energy storage. It is shown that the ability of a current-shaping converter to regulate its output voltage is severely restricted as a result of the energy requirement. The methods and implications of introducing isolation to a shaping ac-dc converter are also studied.
11 Apr 1988
TL;DR: In this article, the effects of switching on the state equation, system stability, DC gain and efficiency are shown for the boost, buck, and buck-boost converters, and it is found that the buck converter is superior to the others from the viewpoints of system stability and DC gain.
Abstract: A model based on practical switches with finite turn-on, turn-off, delay, storage, and reverse recovery times is proposed. The effects of switching on the state equation, system stability, DC gain and efficiency are shown for the boost, buck, and buck-boost converters. The effect of current-based switching-time variation on system stability effect, and the effect of average duty cycle variation on system stability is considered. DC gains of the boost and buck-boost converters are shown to be greatly degraded by switching loss. It is also shown that no additional resistance is generated by switching, in contradiction to previous work. It is found that the buck converter is superior to the others from the viewpoints of systems stability and DC gain, and the efficiencies of all the converters are maximized when the DC gain is close the unity. Previous results are improved and unified using state-space modeling. Analysis results are very simple in spite of the complex switching waveforms. This modeling approach is believed to be very useful for the high-frequency or high-power applications where switching effects become dominant. >
11 Apr 1988
TL;DR: In this article, a novel approach to realizing zero-voltage switching in high-frequency DC/DC converters is presented, utilizing the parasitic associated with the diode stored charge.
Abstract: A novel approach to realizing zero-voltage switching in high-frequency DC/DC converters is presented. Utilizing the parasitic associated with the diode stored charge, it is shown that the diode reverse current established for charge removal can be used advantageously to accomplish soft switching. The entire family of single-transistor DC/DC converters can be realized using the technique. The converter topologies are seen to differ from their hard-switched counterparts only by the presence of a resonant capacitor. It is also shown that device and component stresses are moderate as compared to existing quasi-resonant and resonant techniques. Converter analysis is rather complex as a result of the dominant diode nonlinearities, and no closed-form expressions are possible. Converter transfer characteristics are obtained through simulation, and operating limits are analytically obtained. The concept is validated by experimental results using buck-type converters rated at approximately 100 W and operating at frequencies around 1 MHz. >
11 Apr 1988
TL;DR: Both theory and experiments show that MOSFETs are better switching devices at a power level of about 1 kW, and a systematic way for calculating losses in a PRC operating above resonance is presented.
Abstract: The optimum operating point corresponding to maximum efficiency for a parallel resonant converter (PRC) operating above resonance is obtained. A systematic way for calculating losses in a PRC operating above resonance is presented and illustrated for bipolar and MOS power transistor switches. Experimental results obtained with prototype converters using the above devices are given to support the theory. Both theory and experiments show that MOSFETs are better switching devices at a power level of about 1 kW. >
Patent•
13 Apr 1988
TL;DR: In this paper, the authors describe an apparatus for driving a semiconductor laser device wherein the optical output of the laser device is maintained at a predetermined level by a feedback control, which includes at least two D/A converters.
Abstract: An apparatus for driving a semiconductor laser device wherein the optical output of the laser device is maintained at a predetermined level by a feedback control. The apparatus includes at least two D/A converters. One of the D/A converters is used for conducting a coarse adjustment of the optical output level, and another of the D/A converters is used for conducting a fine adjustment of the optical output level.
TL;DR: In this article, a hybrid power supply for precise regulation of multiple-output voltages is presented, which is composed of an improved forward-type multiple output converter as a preregulator and continuous series regulators using MOSFETs as voltage droppers.
Abstract: A novel hybrid power supply to perform the precise regulation of multiple-output voltages is presented. It is composed of an improved forward-type multiple-output converter as a preregulator and continuous series regulators using MOSFETs as voltage droppers. The steady-state and the dynamic cross-regulation characteristics are analyzed and compared both theoretically and experimentally for the conventional and improved forward-type multiple-output converters. As a result, it is clearly demonstrated that the improved forward-type multiple-output is superior to its conventional counterpart in terms of steady-state and dynamic cross-regulation characteristics, and that the proposed multiple-output power supply has sufficiently precise multiple-output voltage regulation and a satisfactorily high power efficiency. >
02 Oct 1988
TL;DR: The authors present a very versatile experimental method to measure losses in magnetic components and discusses accurate measurement of conduction losses, separation of core and conduction loss, measurement at high frequencies, and scale modeling of magnetic components.
Abstract: Optimization of copper and core losses is an important aspect of converter technology in the trend towards high frequency and high power density, ranging from high-frequency high-Q inductors in resonant converters, to high-power thyristor converters that impress complex current waveforms with significant harmonic content on line frequency transformers and electric machines. Core materials are obtained from manufacturers, so that a designer normally only has the optimization of conduction losses at his or her disposal, after having selected a suitable core material. The authors present a very versatile experimental method to measure losses in magnetic components. They discuss accurate measurement of conduction losses, separation of core and conduction losses, measurement at high frequencies, and scale modeling of magnetic components. The experimental measurements are compared to theoretical predictions of components as applicable to certain power electronic converters. >
01 Feb 1988
TL;DR: In this paper, a series-resonant DC-DC converter operating at a constant frequency above its resonant frequency is analyzed and experimentally tested using a state-plane analysis, the range of load for a given set of circuit parameters over which zero-voltage zero-current turn-on and zerovoltage turn-off (using lossless capacitive snubbers) are calculated and verified on a test circuit.
Abstract: A series-resonant DC-DC converter operating at a constant frequency above its resonant frequency is analyzed and experimentally tested. Using a state-plane analysis, the range of load for a given set of circuit parameters over which zero-voltage zero-current turn-on and zero-voltage turn-off (using lossless capacitive snubbers) are calculated and verified on a test circuit. A digital controller, designed previously for a quantized duty-ratio control in PWM DC-DC converters and now available in a gate array, is used to implement the constant-frequency control of the output voltage. >