V.J. Farias

An electronic ballast with high power factor and low voltage stress

This paper presents a new configuration for an electronic ballast with high power factor for fluorescent lamps. The proposed ballast consists of the integration of a buck-boost converter, used as an input stage to correct the power factor and regulate the voltage on a dc bus, and a resonant half-bridge inverter to drive the lamp. The buck-boost converter operates at a constant frequency and constant duty cycle in a discontinuous conduction mode during all input cycles.

A novel ZCS-ZVS-PWM DC-DC buck converter for high power and high switching frequency: analysis, simulation and experimental results

A DC-to-DC power converter using a zero current switching zero voltage switching PWM (ZCS-ZVS-PWM) cell for high switching frequency and high power operation is presented. The proposed cell consists of only one main switch, plus an auxilliary switch, with ZVS and ZCS switching characteristics, respectively. These switches, associated with a resonant inductor and capacitor, yield zero voltage and zero current switching, providing highly efficient operating conditions for a wide range of power at high switching frequency. Converter control is accomplished by using the PWM technique, with constant frequency operation. A complete analysis of the operating principles, including output characteristics, relevant equations, state space phase, simulation, and experimental results for the buck power converter, is presented.<<ETX>>

A quadratic buck converter with lossless commutation

High switching frequency associated with soft commutation techniques is a new trend in switching converters. Following this trend, the authors present a buck pulsewidth modulation converter, where the DC voltage conversion ratio has a quadratic dependence on duty cycle, providing a large step-down. By introducing two resonant networks, soft switching is attained, providing highly efficient operating conditions for a wide load range at high switching frequency. Contrary to most of the converters that apply soft-switching techniques, the switches presented are not subjected to high switch voltage or current stresses and, consequently, present low conduction losses. The authors present, for this converter, the principle of operation, theoretical analysis, relevant equations and simulation and experimental results.

An optimum ZVS-PWM DC-to-DC converter family: analysis, simulation and experimental results

The authors consider a family of DC-to-DC power converters using the lossless commutation pulse-width-modulation (PWM) source feeding resonant disconnecting circuit cell with resonant cycle interruption (LC-PWM-SF-RDC) to overcome the problems present in quasi-resonant converters (QRCs) and QRCs-PWM. The most important property of this family of devices is the ability to regulate output power and voltage by PWM, with constant operating frequency, without load limitation, and without sacrificing the lossless commutation. The authors present the operating principle and design-oriented analysis, output characteristics, relevant equations, and simulation results. These procedures are validated by a prototype laboratory implementation.<<ETX>>

A proposal of Led Lamp Driver for universal input using Cuk converter

In recent years, light emitting diodes (LEDs) have become a viable alternative to conventional light sources. The LEDs are now approaching performance levels that make them attractive for use in several illumination applications. One of the main advantages of LEDs is their very long life that it is also related directly with the maintenance of the LED current, preventing the device overheating. To contribute with the advantages of the LEDs, the same ones need efficient drivers with optimized control circuitry. The main focus of this paper is to improve the LED driver characteristics using microcontrolled Cuk converter, therefore, greater durability and efficiency can be achieved and working for different nominal values of voltage, from an universal input voltage or battery. Mathematical analysis and experimental results are presented to the drive of an LED lamp of 11 W built with 10 power LEDs Creereg XLampreg XR-C.

A high power factor ballast using a single switch with both power stages integrated

This paper presents a high power factor electronic ballast used to startup fluorescent lamps employing a single power stage and a single-switch. This topology was obtained combining of a Boost converter and a new inverter topology with coupled inductors. The use of a single active switch reduces the number of components used in the control and power circuits. The equations used for designing the proposed reactor and for choosing the semiconductor devices are presented. A prototype operating at 50kHz was built and used to startup 40-W fluorescent lamps.

Stand-alone photovoltaic energy storage system with maximum power point tracking

This digests deals with the study of a stand-alone photovoltaic system, which is able to extract the maximum power from photovoltaic array for all solar intensity conditions and to provide output voltage regulation. The proposed system consists of a DC-DC converter in combination with battery energy storage in a simple structure. Operating principle and control strategy are described. Digital simulation is included, supporting the validity of the concept.

A buck quadratic PWM soft-switching converter using a single active switch

High-switching frequency associated with soft commutation techniques is a trend in switching converters. Following this trend, a buck pulsewidth modulation (PWM) converter is presented. The DC voltage conversion ratio of this converter has a quadratic dependence on duty cycle, providing a large stepdown. This new buck quadratic PWM soft-single-switched converter, having only a single active switch, provides a high efficient operating condition for a wide load range at high-switching frequency. In order to illustrate the operating principle of this new converter, a detailed study including theoretical analysis, relevant equations and simulation, and experimental results is carried out.

A boost PWM soft-single-switched converter with low voltage and current stresses

This paper is an improved version of a previous study that described a boost pulse-width-modulated (PWM) soft-single-switched power converter, which, having only a single active switch, is able to operate with soft switching in a PWM way without high voltage and current stresses. In addition, such a power converter can work at high-switching frequencies for a wide load range. In order to illustrate the operating principles of this power converter, a detailed study, including simulations and experimental tests, is carried out. The validity of this power converter is guaranteed by the obtained results.

Proposal of a Soft-Switching Single-Phase Three-Level Rectifier

This paper is concerned with the study of a single-phase boost-type three-level rectifier. The converter is supposed to present high input power factor, low current harmonics, low total harmonic distortion, and simple control scheme. In order to minimize switching losses, a passive nondissipative snubber is associated with the aforementioned converter. The theoretical analysis, design procedure, and analytical results regarding a 1.2-kW prototype are presented to validate the proposal.