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34 results on '"Pinheiro, J. R."'

7. An imroved design for ZVT DC-DC PWM converters with snubber assisted auxiliary switch

Author

Russi, J., Martins, M. L., Gründling, H. A., Pinheiro, H., Pinheiro, J. R., and Hey, H. L.

Subjects
projeto de conversores, converters design, ZVT, Comutação suave, Soft-switching
Abstract

This paper proposes an improved design to calculate the snubber auxiliary elements of ZVT DC-DC PWM converters with snubber assisted auxiliary switch. The proposed improved design guidelines are based on the reduction of the conduction losses through the auxiliary circuit. It is accomplished by the unique location of the turn-off snubber capacitor, which is shared by both active switches. By means of this improved design guidelines the converter efficiency can be increased. An efficiency comparative analysis is carried out and the experimental results, obtained from 1 kW, 100 kHz laboratory prototypes, show a relevant improvement in converter efficiency compared to the original converter design. In addition, experimental results also confirm that with the improved design the ZVT PWM converters with snubber assisted auxiliary switch can be competitive with ZVT PWM converters with constant auxiliary voltage source (True PWM ZVS pole). Este artigo propõe uma metodologia de projeto aprimorada para determinação dos componentes auxiliares para o conversor ZVT CC-CC PWM snubber assisted auxiliary switch. O procedimento de projeto proposto é baseado na redução das perdas de condução no circuito auxiliar. Isto é somente possível devido à localização do capacitor snubber de bloqueio, o qual é compartilhado por ambas as chaves ativas. Através do procedimento de projeto proposto o rendimento do conversor pode ser aumentado. Uma análise comparativa do rendimento é apresentada e os resultados experimentais, obtidos de protótipos de laboratório de 1 kW, 100 kHz, mostram uma melhoria relevante em relação ao rendimento apresentado pelo projeto original. Além disso, os resultados experimentais também confirmam que o projeto proposto para o conversor ZVT snubber assisted auxiliary switch torna-o competitivo em relação ao conversor ZVT PWM com fonte auxiliar de tensão constante (true PWM ZVS pole).

Published
2005

8. A family of improved ZVT PWM converters using an auxiliary resonant source

Author

Martins, M. L., Pinheiro, H., Pinheiro, J. R., Gründling, H. A., and Hey, H. L.

Subjects
Transição Sob Tensão Nula, DC-DC Converters, Conversores CC-CC, Fonte Auxiliar Ressonante, Auxiliary Resonant Source, Zero-Voltage Transition
Abstract

This paper presents a novel family of Zero Voltage Transition (ZVT) DC-DC PWM Converters that uses a resonant circuit as auxiliary commutation source to control the current through the auxiliary switch without additional current stresses on main devices. The improved ZVT commutation cell enables the main switch to be turned on and off at Zero Voltage Switching (ZVS) and the auxiliary switch to be turned on and off at Zero Current Switching (ZCS) from zero to full-load. Este trabalho apresenta uma nova família de conversores CC-CC PWM ZVT os quais utilizam um circuito ressonante como fonte auxiliar para controlar a corrente através da chave auxiliar sem agregar esforços adicionais de corrente nos dispositivos principais. A célula de comutação aperfeiçoada possibilita a comutação da chave principal sob tensão nula e a comutação da chave auxiliar sob corrente nula desde carga nula até carga nominal.

Published
2003

22. Comparison of Linear Quadratic Controllers with Stability Analysis for DC- DC Boost Converters Under Large Load Range.

Author

Dupont, F. H., Montagner, V. F., Pinheiro, J. R., Pinheiro, H., Oliveira, S. V. G., and Péres, A.

Subjects
H2 control, LINEAR systems, ROBUST stability analysis, DC-to-DC converters, LYAPUNOV functions, LINEAR matrix inequalities
Abstract

This paper presents four different control design strategies for linear quadratic regulators applied to DC- DC boost converters operating under large load range, pointing out advantages and drawbacks by means of a performance comparison. Two of the strategies are based on single controllers and the other two use a set of local controllers to cope with the entire load range. The robust stability of the closed-loop linearized system with the four control strategies is investigated via the existence of a common Lyapunov function, obtained in a fast and efficient way by the solution of linear matrix inequality conditions. [ABSTRACT FROM AUTHOR]

Published
2013
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23. Integrated auxiliary commutation circuits: a generalised approach.

Author

Schuch, L., Rech, C., and Pinheiro, J. R.

Abstract

The concept of integrated auxiliary commutation circuits (iACCs) applied to systems with several power conversion stages is proposed. This concept has two main objectives, namely: to reduce the number of additional elements to accomplish the soft-switching and to use the circulating energy from one commutation to assist another one, so that the efficiency is improved without penalising the cost of the system. Some rules to obtain new iACCs are presented. New iZVT circuits are applied to a double-conversion UPS to illustrate the functionality and applicability of this concept. By using these circuits, the main switches operate under soft-commutation of ZVT type, and the auxiliary switches are turned on and off under ZCS or ZVS. Experimental results of three prototypes (1.2 kW at 100 kHz) are presented to demonstrate the good performance of the new integrated ZVT ACC and the feasibility of the proposed concept. [ABSTRACT FROM AUTHOR]

Published
2009
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34. Molecular Signature in the Photoluminescence of α-Glycine, L-Alanine and L-Asparagine Crystals: Detection, ab initio Calculations, and Bio-sensor Applications.

Author

Caetano, E. W. S., Pinheiro, J. R., Zimmer, M., Freire, V. N., Farias, G. A., Bezerra, G. A., Cavada, B. S., Fernandez, J. R. L., Leite, J. R., de Oliveira, M. C. F., Pinheiro, J. A., de Lima Filho, J. L., and Leite Alves, H. W.

Subjects
*MOLECULES, *PHOTOLUMINESCENCE, *GLYCINE, *ALANINE, *ASPARAGINE, *CRYSTALS, *BIOSENSORS
Abstract

We present the photoluminescence spectra of α-glycine, L-alanine, and L-asparagine crystals. They are broad and structured, comprising green to ultraviolet emission in the 1.75–3.60 eV range. Absorption measurements show that the band gap energies of the crystals are of the order of 5.0 eV. Ab initio calculations of their electronic structures allow for the assignment of the observed peaks in the visible region to lattice-related processes of exciton nature associated with polaron levels. The very thin photoluminescence peaks in the ultraviolet region are assigned to intramolecular transitions, being a signature of the weakly interacting amino acid molecules in the crystals. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2005
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