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Circuits and Systems I: Fundamental Theory and Applications, IEEE Transactions on

Issue 8 • Date Aug. 1997

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Displaying Results 1 - 18 of 18
  • Guest Editorial

    Publication Year: 1997 , Page(s): 657 - 659
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  • Identification and control of power converters by means of neural networks

    Publication Year: 1997 , Page(s): 735 - 742
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    This paper investigates the use of neural networks for identification and control of power converters. A nonparametric model of a dc-to-dc switching converter implemented by means of a neural network emulator identifies the converter dynamics in cases of uncertainty in the load parameter. A pseudo-linearization control technique resulting in converter regulation and closed-loop linear dynamic behavior is also implemented by means of a neural controller. Simulation results in a PWM boost converter under large-signal operation illustrate both applications This paper investigates the use of neural networks for identification and control of power converters. A nonparametric model of a dc-to-dc switching converter implemented by means of a neural network emulator identifies the converter dynamics in cases of uncertainty in the load parameter. A pseudo-linearization control technique resulting in converter regulation and closed-loop linear dynamic behavior is also implemented by means of a neural controller. Simulation results in a PWM boost converter under large-signal operation illustrate both applications View full abstract»

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  • Sliding mode control of a DC/DC PWM converter with PFC implemented by neural networks

    Publication Year: 1997 , Page(s): 743 - 749
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    An experimental neural controller implementing a variable structure control (VSC) algorithm is proposed for a power factor preregulator. VSC control laws yield fast response and a robust behavior against large parameters variations. A multilayer perceptron learns through backpropagation to approximate the desired adaptive control functions. The main advantage of the neural network implementation in comparison to the numerical implementation is that decreases complexity and cost of the controller, and increases the switching frequency. A simple analog electronic realization of this neural network using discrete operational amplifiers is proposed. This implementation possesses all good properties of sliding mode while avoiding the unnecessary discontinuities of the control input signals and thus eliminating chattering. Experimental results are summarized confirming the validity of the neural network approach View full abstract»

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  • A family of ZVS-PWM active-clamping DC-to-DC converters: synthesis, analysis, design, and experimentation

    Publication Year: 1997 , Page(s): 698 - 704
    Cited by:  Papers (28)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    This paper presents a technique to generate a complete family of two-switch pulsewidth-modulated (PWM) with active clamping DC/DC converters, featuring soft commutation of the semiconductors at zero-voltage (ZVS). The main purpose of this technique is to integrate these converters under a same theoretical principle to derive the topologies in a comprehensive form and generate new circuits. All the converters have the advantage of soft commutation (ZVS) with minimum switch voltage stress due to the clamping action. Besides operating at constant frequency and with reduced commutation losses, these converters have output characteristics similar to the PWM hard-switching counterpart, which means that there is no circulating reactive energy that would cause large conduction losses. Principle of operation, theoretical analysis, simulation and experimental results of one particular converter taken as an example, are provided in this paper View full abstract»

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  • Analysis and design of hybrid parallel-series resonant converter

    Publication Year: 1997 , Page(s): 705 - 711
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    Fixed and variable frequency operation of a high-frequency transformer isolated dc-to-dc converter employing hybrid parallel-series resonant converter bridge operating in continuous current mode is proposed. State space analysis method is used to analyze the converter for continuous and discontinuous capacitor voltage modes of operation. Based on the analysis, normalized design curves for the converter gain, and other peak component stresses are obtained. A design example is presented. All the results obtained from the analysis are verified with SPICE3 simulation and experimental results, for a 300 W output converter View full abstract»

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  • Distributed interleaving of paralleled power converters

    Publication Year: 1997 , Page(s): 728 - 734
    Cited by:  Papers (91)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (148 KB)  

    This paper introduces a distributed approach to interleaving paralleled power converter cells. Unlike conventional methods, the distributed approach requires no centralized control, automatically accommodates varying numbers of converter cells, and is highly tolerant of subsystem failures. A general methodology for achieving distributed interleaving is proposed, along with a specific implementation approach. The design and experimental verification of a 50 kHz prototype system is presented, and quantitative performance comparisons are made between synchronized clocking, independent clocking, and interleaved clocking of the converter cells. The experimental results corroborate the analytical predictions and demonstrate the tremendous benefits of the distributed interleaving approach View full abstract»

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  • Modeling of periodically switched networks by mixed s-z description

    Publication Year: 1997 , Page(s): 750 - 758
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    A new description of linear periodically time-varying systems is proposed. To describe simultaneously the continuous and discrete time nature of the system, the generalized transfer function of the Laplace and discrete operator is introduced. This mixed description includes the transfer functions of continuous time and discrete time systems as limiting cases. Special attention is paid to two-phase switched circuits and results of computer simulations are presented View full abstract»

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  • Fast time-domain simulation by waveform relaxation methods

    Publication Year: 1997 , Page(s): 660 - 666
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (160 KB)  

    Fast time-domain simulation of power electronic systems by using waveform-relaxation methods is presented. Algorithms for circuit partitioning, time windowing, and simulation scheduling are developed. Practical implementation of the partitioning algorithm based on modal analysis is also discussed. Feasibility and advantages of applying these methods to power electronic systems are demonstrated by simulation results for a series resonant converter and a boost zero-voltage-transition PWM converter View full abstract»

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  • A unified approach to analysis and design of random pulsewidth modulation in voltage-source inverters

    Publication Year: 1997 , Page(s): 763 - 766
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (160 KB)  

    Analysis of spectral effects of random pulsewidth modulation (RPWM) in voltage-source inverters is presented. The randomized parameter is the width of individual switching intervals, and it is shown that the optimal solution consists in random selection of only two width values whose ratio is not an integer. For the optimal randomization scheme, powers in the dc and fundamental components of the switching function are determined, while the whole remaining power appears as noise. A closed-form expression for the noise spectral density is given. The developed theory provides better understanding of effects of random-width modulation on the power spectrum of inverter output voltage, and allows explicit design of RPWM strategies satisfying specified criteria of spectral optimization. Theoretical considerations are illustrated by computational examples View full abstract»

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  • Analysis of power electronic converters using the generalized state-space averaging approach

    Publication Year: 1997 , Page(s): 767 - 770
    Cited by:  Papers (51)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB)  

    Power electronic converters are periodic time-variant systems, because of their switching operation. The generalized state-space averaging method is a way to model them as time independent systems, defined by a unified set of differential equations, capable of representing circuit waveforms. Therefore, it can be a convenient approach for designing controllers to he applied to switched converters. This brief shows that the generalized state-space averaging method works well only within specific converter topologies and parametric limits, where the model approximation order is not defined by the topology number of components. This point is illustrated with detailed examples from several basic dc/dc converter topologies View full abstract»

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  • Analysis of networks with ideal switches by state equations

    Publication Year: 1997 , Page(s): 692 - 697
    Cited by:  Papers (27)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB)  

    A new computer-oriented method for a large-signal time-domain analysis of networks containing ideal switches is presented. The method is based on a state variable approach that exploits an efficient novel algorithm developed for the systematic formulation of state equations and output equations for linear active networks. Switched networks consisting of linear elements and both externally and internally controlled switches can be investigated. Dirac's delta impulses are permitted in the analysis in order to find out the correct topology after switching. A new simple and convenient method for representing Dirac's delta impulses is also introduced. An example is both discussed in detail and analyzed with a computer code View full abstract»

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  • Current spectra translation in single phase rectifiers: implications to active power factor correction

    Publication Year: 1997 , Page(s): 771 - 775
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    This brief examines the input and output current spectra translation of a line commutated single phase full wave rectifier. Analytical expressions for the spectra translation of the current harmonics are derived. The proposed method is then used to quantify the contribution of a current-loop with finite bandwidth to the overall total harmonic distortion (THD) budget in average current mode active power factor correction (APFC) systems. The proposed theory is supported by computer simulation View full abstract»

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  • New directions in DC-DC power conversion based on idealized concepts leading ultimately to the asymmetrical duty-cycle power converter

    Publication Year: 1997 , Page(s): 722 - 727
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB)  

    Following the precepts of an ideal DC-DC power converter, the asymmetrical duty-cycle power converter, a zero-switching loss converter, is, in a demonstrable way, a new direction in DC power conversion. Its benefits include low conduction loss, low EMI generation, and lossless switching. This paper includes conceptual discourse on the nature of the asymmetrical converter, as well as experimental results View full abstract»

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  • Design of feedback gain vector of two-state basic PWM multifeedback regulators for large-signal stability

    Publication Year: 1997 , Page(s): 676 - 683
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    A method for determining boundaries on the feedback gains in a switching regulator with multiple feedback, in order to ensure stability for large changes in the load values, is developed. Using an original approach for time-domain analysis, a large-signal, nonlinear, discrete-time model of the closed-loop converter is obtained; the model's equations are expressed in disturbances of the state variables due to disturbance in the load. The first step toward a global stability design is to find the constraint that ensures local stability around the operating point: the nonlinear terms (products of disturbances) are neglected in the model, the z-transform is applied to the linearized equations, and the condition that the eigenvalues are situated inside the unit circle is imposed. The nonlinear model, including the nonlinearity of the pulsewidth modulation (PWM), due to possible saturation, is then considered. A new constraint in terms of feedback gains is found in order to ensure that one and only one real equilibrium point (i.e., the quiescent operating point) exists. Putting together the constraints, boundaries on the feedback gains are found. The method is developed for converters containing two reactive elements, operating in continuous conduction mode. An example of a boost converter with inductor current and output voltage feedback is presented in detail. The large-signal stability of the design is checked by using the state-plane portrait and time-domain simulation View full abstract»

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  • Zero-order switching networks and their applications to power factor correction in switching converters

    Publication Year: 1997 , Page(s): 667 - 675
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    This paper addresses the requirements of networks containing linear inductors, capacitors and ideal switches for synthesis of zero-order input impedance. Sufficient conditions for achieving zero-order input impedance are stated in terms of the network topology and the switching sequence. Such networks have direct practical relevance to power factor correction (PFC). Based on zero-order switching networks, a comprehensive study is presented for many existing PPC circuits as well as new circuit topologies View full abstract»

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  • Modern CAD methods for analysis of switched networks

    Publication Year: 1997 , Page(s): 759 - 762
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (76 KB)  

    The authors have worked in computer-aided design (CAD) and in simulation of switched networks over many years. In this brief, they consider all CAD aspects related to simulation of these networks and present practical suggestions and methods useful for analysis in time and frequency domain View full abstract»

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  • Realizability conditions and bounds on synthesis of switched-capacitor DC-DC voltage multiplier circuits

    Publication Year: 1997 , Page(s): 684 - 691
    Cited by:  Papers (58)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    A formal study of the theoretical performance of switched-capacitor (SC) dc-dc voltage multiplier circuits is given. A question concerning the necessary number of circuit elements to realize a given conversion ratio is addressed. In response to the question the bound on attainable voltage ratio for a given number of capacitors k and the bound on the number of switches required in any circuit configuration have been established. The maximum step-up or step-down ratio is given by the kth Fibonacci number, while the bound on the number of switches required in any SC circuit is 3k-2. The complete set of attainable DC conversion ratios is found. A canonical circuit realization of the maximum voltage ratio is discussed and illustrative examples are included. Necessary and sufficient conditions for the realizability of a dc conversion ratio are determined and formal proofs are given View full abstract»

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  • Advances in high-frequency power conversion by delta-sigma modulation

    Publication Year: 1997 , Page(s): 712 - 721
    Cited by:  Papers (20)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    The delta-sigma technique has been recently proposed for power processing and the idea is particularly attractive in audio power amplifying area. This paper aims to apply this technique to high-frequency power conversion. The well known switching power supply topologies have been revised for this purpose. A laboratory prototype of a suitable power converter has been realized and tested. Analysis, experimental results and evaluation on efficiency and power range are presented View full abstract»

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