Showing papers on "Converters published in 1993"

Power Electronics: Circuits, Devices and Applications

Abstract: 1. Introduction. 2. Power Semiconductor Diodes and Circuits. 3. Diode Rectifiers. 4. Power Transistors. 5. DC-DC Converters. 6. Pulse-width Modulated Inverters. 7. Thyristors. 8. Resonant Pulse Inverters. 9. Multilevel Inverters. 10. Controlled Rectifiers. 11. AC Voltage Controllers. 12. Static Switches. 13. Flexible AC Transmission Systems. 14. Power Supplies. 15. DC Drives. 16. AC Drives. 17. Gate Drive Circuits. 18. Protection of Devices and Circuits. Appendices: Three-phase Circuits, Magnetic Circuits, Switching Functions of Converters, DC Transient Analysis, Fourier Analysis, Thyristor Commutation Techniques, Data Sheets.

Novel zero-current-transition PWM converters

Abstract: A new family of zero-current-transition (ZCT) pulse-width-modulated (PWM) converters are proposed. The new family of converters implements zero-current turn-off for power transistor(s) without increasing voltage/current stresses and operates at a fixed frequency. The proposed converters are deemed most suitable for high-power applications where the minority-carrier semiconductor devices (such as IGBTs, BJTs, and MCTs) are predominantly used as the power switches. Theoretical analysis is verified on a 100-kHz, 1-kW ZCT-PWM boost converter using an IGBT. >

A Wavelength-Convertible Optical Network

Abstract: Wavelength-division multiplexing is emerging as the dominant technology in future all-optical network. To efficiently use the wavelengths, wavelength converters are employed for a circuit-switched optical network in which a circuit can change its wavelength to resolve wavelength conflicts and to reuse the wavelengths. To improve the efficiency, a few converters are provided and shared by the incoming circuits in the share-per-node or the share-per-link wavelength-convertible switch. A heuristic algorithm for dynamic routing is used to reduce the number of converters. Performance gain in call blocking probability and fairness and in the reduction of the number of converters are shown

Power-factor correction with interleaved boost converters in continuous-inductor-current mode

Abstract: The operation and design trade-offs of the interleaved boost converter in continuous inductor-current mode in a high-power-factor preregulator circuit are investigated. By using interleaved converters, an overall reduction of boost inductor and electromagnetic interference (EMI) filter volume can be achieved, together with reduced switching losses. The problem of unequal load sharing between the interleaved power stages with average current control is pointed out, and a practical solution is recommended. EMI filter design considerations and experimental data taken from a 3 kW converter are presented. >

Energy-conservation approach to modeling PWM DC-DC converters

Abstract: A systematic method is presented for including parasitic resistances and offset voltage sources of power switches in averaged dynamic large-signal, DC, and small-signal circuit models of pulse-width modulated (PWM) converters operating in continuous conduction mode (CCM). This method is based on the principle of energy conservation. The approach takes into account the inductor current ripple. For zero-ripple current, the method gives the same results as the state-space averaging method. Reflection rules are introduced and used to simplify the models. As an example, a modeling procedure for the PWM buck converter is detailed. >

Multilevel converters for high power AC drives: a review

Abstract: The multilevel approach appears to be very promising in AC motor drives, especially when both reduced harmonic contents and high power are required. Several topologies of multilevel voltage source power converters structures are presented and discussed, with particular reference to the modulation techniques which rule the power converters interfacing with the AC drives processes. >

Force commutated HVDC and SVC based on phase-shifted multi-converter modules

Abstract: The authors examine how presently available gate-turn-off thyristors (GTOs), which are still relatively slow, can be used in force-commutated high-voltage direct-current (HVDC) and static VAR compensator (SVC) converters by employing multiconverter modules in conjunction with a phase-shifting principle which cancels the undesirable switching harmonics. They point out that incorporating the sinusoidal pulse-width modulation (SPWM) technique enables feedback control, active filtering and regulatory functions to be performed by the converters. This is because a reasonable bandwidth of the modulating signal is transmitted by the multiconverter station in spite of the low switching rates of the GTO valves. >

An improved LQR-based controller for switching DC-DC converters

Abstract: A general approach for controlling pulse-width-modulated (PWM) -type switching DC-DC converters digitally using state-feedback techniques and linear optimal control theory is reported. The methodology for redesigning the state estimator is investigated, and a method derived from the general linear-quadratic-regulator (LQR) problem, is proposed. The method is found to offer better transient responses and robustness to uncertainties in plant parameters when compared with the typical eigenvalue-assignment method. Special attention is directed to plant models with possible migrations of the open-loop zeroes across the stability boundary during operation. Results of applying these techniques to a published Cuk converter are reported to illustrate different points of interest. >

Design of the zero-voltage-switching quasi-square-wave resonant switch

Abstract: Zero-voltage-switching, quasi-square-wave (ZVS-QSW) power converters with controllable rectifiers feature constant-frequency, PWM-like operation with low voltage and relatively low current stresses on active devices. New closed-form analytic results are derived and applied to construct a detailed design procedure for the ZVS-QSW switch. Starting with usual design constraints, resonant elements are selected so that zero-voltage switching is achieved under all operating conditions, with favorable tradeoff between switching and conduction losses. Results are derived in a form applicable to a wide variety of ZVS-QSW power converter topologies. The design procedure is illustrated on a flyback power converter example and is supported by simulation results. >

Load-current-sharing control for parallel operation of DC-to-DC converters

Abstract: The control strategy for parallel operation of multiple converters is investigated. Analysis and design considerations of load-current sharing for the parallel system are presented and the superiority of current-balance control is discussed. The prominent features of the load-current sharing and analytical results are confirmed experimentally for a three-paralleled forward-converter system. >

A family of DC-to-DC PWM converters using a new ZVS commutation cell

Abstract: A commutation cell is proposed that is destined to replace the conventional hard switched one in PWM DC-DC converters, with the following advantages: commutation at zero-voltage for both the active and the passive semiconductor, PWM at constant frequency, no overvoltage across the switches, and no additional current stress in comparison to the hard switching converter counterpart. Auxiliary components rated at very small current are used. Both the main and the auxiliary switches are gated by the same signal, rendering simple the drive circuitry. The principle of operation and analysis are provided. Experimental results obtained from a prototype rated at 300 V and 1.2 kW are also presented. >

Average simulation of PWM converters by direct implementation of behavioral relationships

Abstract: Average modeling of PWM power converters is reexamined in the light of the behavioral dependent sources now included in modern versions of electronic circuit simulators. A topology independent behavioral model is developed to emulate the operation of PWM converters in voltage and current modes, for continuous and discontinuous inductor current cases. It is shown that, in general, the operation of the switching part involves three behavioral blocks, i.e., the generic switched inductor model (GSIM), the duty cycle generator (DCG), and the inductor current generator (ICG). Explicit expressions and equivalent circuits are developed for all possible modes of operation. >

Economic single-phase to three-phase converter topologies for fixed and variable frequency output

Abstract: Several component-minimized circuit topologies for single-phase to three-phase conversion are proposed. The topologies employ fewer semiconductor devices and generate high-quality output voltages. Suitable modification to achieve active input current shaping 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 for facilitating circuit design are presented. Selected results are verified experimentally on laboratory prototype converters. >

A simple and efficient synchronous rectifier for forward DC-DC converters

Abstract: A simple and efficient MOSFET synchronous rectification circuit suitable for forward DC-DC power converters is proposed. The main feature of this circuit is the addition of a capacitor in parallel with the drain source of the MOSFET used as a rectifying device. This capacitor extends the conduction period of the MOSFET used as a freewheeling device. As a result, a 92% efficiency at 5 V for 10 A output is achieved. >

Power converters as natural gyrators

Abstract: The authors investigate the open-loop gyrator behavior of a class of DC-DC converters that are characterized by double bridges. If the switching frequency of the double bridge converter is high enough with respect to its natural frequencies, the converter can be viewed as a gyrator from its terminals. Unlike other gyrator modeling approaches for converters, the double bridge converters naturally behave as gyrators without any extra control circuits. >

Active clamp PWM forward converter with self driven synchronous rectification

Abstract: The necessity of developing high efficiency and high power density on board DC/DC power converters with low output voltage for telecommunication applications leads to substitution of the rectifier diodes of the output stage by synchronous rectifiers. Control complexity and driving losses are the main constraints of this technique. A very simple implementation of self driven synchronous rectification in the active clamp PWM forward power converter is proposed. The absence of control circuitry and the minimization of losses are the main benefits of this circuit, whose analysis and optimization are addressed. Very high overall efficiency (89%) has been obtained in an actual prototype (3.3 V, 20 A). >

Primary side controller for regulated power converters

Abstract: A primary side controller for regulated power converters may be implemented as a monolithic integrated circuit in which fewer pins are required as compared to the prior art 3842 controller. The present controller includes a current limit protection function having an extended time period over which a predetermined current value is reached.

Zero-voltage-transition pulse-width-modulated converters

Abstract: To date, soft-switching techniques applied to the PWM converters, with the exception of a few isolated cases, are subjected to either high switch voltage stresses or high switch current stresses, or both. This invention presents a new class of zero-voltage-transition PWM converters, where both the transistor and the rectifier operate with zero-voltage switching, and are subjected to minimum voltage and current stresses. Breadboarded converters are constructed to verify the novelty of the proposed new family of converters.

Computer-Aided Analysis and Design of Switch-Mode Power Supplies

Abstract: Switch-Mode Power Supply Fundamentals Low-Frequency Behaviour Models of Square-Wave Power Converters Analysis of Square-Wave Power Converters Power Converters with Transformer Isolation Voltage-Mode and Current-Mode Controlled Switching Regulators Cycle-By-Cycle Simulation of Power Converter Circuits Simulation of Low-Frequency Behaviours of Converters Computer-Aided Design of Converters and Regulators High-Frequency Quasi-Resonant and Resonant Converters Practical Techniques of Design of Switch-Mode Power Supplies Appendices: An Introduction to SPICE Summary of Commonly Used SPICE Statements Nonconvergence and Related Problems in SPICE About PSpice

Power conversion array applying small sequentially switched converters in parallel

Abstract: Decreased input and output ripple current and ripple voltage on a switched mode power conversion array is realized at high power levels and frequencies by coupling an input power signal across an input capacitance to which a plurality of smaller power converter circuits are coupled in parallel. The converter circuits may have any topology now known or later devised. Each of the converter circuits are sequentially operated in a phase shifted manner across the period of the conversion frequency in a time overlapping relationship. For example, if there are N converters and the period of the conversion frequency is T, each converter circuit is triggered or switched at a phase shift corresponding to a time increment of T/N delayed with respect to the preceding or subsequent converter. The output of each of the converters is then coupled in parallel to an output capacitance. The operation of the converters may each be regulated in any manner now known or later devised and are shown in the illustrated embodiment as being pulse width modulated to provide a regulated output.

Zero-voltage-transition switching power converters using magnetic feedback

Abstract: A soft-switching circuit for achieving zero-voltage-transition (ZVT) type commutation in switching power converters includes a magnetic feedback circuit for achieving substantially zero voltage turn on of the active power switches and for achieving zero voltage turn off of the passive power switches of the switching power converter.

A comparison between hysteretic and fixed frequency boost converters used for power factor correction

Abstract: A hysteretic controlled boost power converter is compared to a fixed frequency boost converter. The decision of which circuit to be used in electronic products is often based upon cost, size, heat rise, availability of components, and complexity of the design. The advantages and disadvantages of the hysteretic control and fixed frequency boost converter using 400 W as a load operating from 90 VAC to 270 VAC are providing 450 V to the output electrolytic capacitor are presented. >

Sliding modes in power converters and motion control systems

Abstract: The VSS approach to the design of a control for power converters and motion control systems is presented in this paper. The structure of the control system is intentionally selected to resemble the cascade systems in order to apply the digital signal processing for implementation into the Variable Structure Systems (VSS) with sliding modes. First, the mathematical description of the power converters and robotic manipulators with electrical machines are derived in the form suitable for analysis. Then, the following problems are discussed: selection of the switching functions in the form that allows clear separation of the fast and slow motions of the system: design of cascade VSS with inner current loop and the influence of parameter uncertainties on the system motion. Proposed algorithms are verified by simulation and experiments. Simulation and experimental results are presented.

Application of the principle of energy conservation to modeling the PWM converters

Abstract: Parasitic resistances and offset voltage sources of power switches are included in the averaged-circuit models of an actual switching part of PWM transformerless converters which operate in a continuous conduction mode. The actual switching part is divided into the ideal switching part and its parasitics. It is shown that the ideal switching part can be modeled by one of 24 equivalent averaged circuits, each consisting of a dependent current source and a dependent voltage source. The parasitics are averaged using the principle of energy conservation. The obtained nonlinear large-signal model of the actual switching part can be placed into the buck, boost, and buck-boost topologies leading to averaged-circuit models of power stages. Linearization of the model around a DC operating point results in DC and small-signal models of the converters. Reflection rules are established which can be used to simplify the circuit models. The proposed method is illustrated by modeling the PWM boost converter. >

Analog interfaces for digital signal processing systems

Abstract: Foreword. Preface. 1. The Power Consumption of CMOS Wideband Amplifiers. 2. Low-Distortion CMOS Amplifier Design. 3. Oversampled A-to-D and D-to-A Converters. 4. Higher-Order Sigma-Delta A-to-D Converters. 5. The Practical Implementation of Sigma-Delta D-to-A Converters. Index.

Elevator control apparatus using parallel converters and inverters with means to control circulating current

Abstract: The present invention provides an elevator speed control system in one mode, including: a plurality of converters connected in parallel for converting an AC voltage to a DC voltage by means of controllable devices; a capacitor for smoothing output voltages of the plural converters; a plurality of inverters connected in parallel which convert the voltages smoothed by means of the capacitors to an AC voltage whose magnitude and frequency are controllable, and which further supply the resulting AC voltage to a hoisting induction motor; current detectors for detecting the currents in each phase of the plural converters and inverters; a control means which calculates the sum of the resulting currents of the plural converters and inverters and which further controls the output voltages of plural converters and inverters so that the resulting sum is minimized. In another mode of the present invention, there is provided a control means which calculates the difference in phase between output voltages of the plural converters and inverters, and which stops the plural converters or inverters if the calculated phase difference exceeds a predetermined value. In the above configurations, the reduction in output is effectively avoided by suppressing the circulating current flowing through the parallel-connected converters or inverters.

Comparison of EMI performance of PWM and resonant power converters

Abstract: When utilized in a power supply, hard switching and soft switching converters have different noise performances. Depending on their power, frequency range, and application, zero-current switching (ZCS) and zero-voltage switching (ZVS) techniques can significantly lower the noise. This work characterizes and compares the conducted and radiated electromagnetic interference (EMI) performance of hard and soft switching, including both ZVS and ZCS converters. An experimentally tested topology selection procedure for EMI minimization in power supplies is presented. The effects of increasing the switching and resonant frequencies and of utilization of snubbers and integrated control circuits for the purpose of EMI reduction are studied and demonstrated. >

Analysis of fuzzy control method applied to DC-DC converter control

Abstract: The application of fuzzy control to DC-DC converters operating at finite switching frequency is studied. Several control methods used for buck and boost converters are compared to the fuzzy converter control. Simulation results for several control methods are presented. The simulations show that the fuzzy control method has better dynamic performance and less steady state error. >

Robust control of multimodule current-mode controlled converters

Abstract: A robust controller for multimodule current-mode push-pull converters is presented First, the small-signal equivalent circuit and the transfer function model of the multimodule converter system are obtained Then, the selection of slope compensation and the model reduction are performed using the concept of dominant energy mode Based on the reduced converter model, a PI (proportional plus integral) controller is quantitatively designed according to the prescribed regulating specifications using a systematic design procedure A robust controller is proposed and augmented to improve the control performance when the parameter variations caused by system configuration change and operating point shift have occurred The performance of the converter and the effectiveness of the proposed controller are demonstrated by simulation and experimental results >