Síntese de conversores ressonantes com alto fator de potência e alta eficiência para o acionamento de diodos emissores de luz

Abstract

This work presents a study regarding the driving of light-emitting diodes (LEDs) fed from mains power. This study involves an analysis of the thermal, electrical and photometrical characteristics of the LEDs, aiming an adequate static and dynamical characterization of the load. Then, with the goal of proposing driving converters with a superior global efficiency, it is proposed the use of resonant conversion as the power control stage of the LED drivers. This stage is preceded by a power factor pre-regulator stage, so that a low total harmonic distortion on the input current can be achieved. A systematic study of the power factor correction topologies and resonant converters which might compose each of these two stages is done, therefore compiling the characteristics, advantages and disadvantages of each for the driving of LEDs. From this study, it was proposed an integrated converter structure of a resonant converter with a high power factor pre-regulator, which showed good compliance when driving an LED load composed of 72 series-associated LEDs, with nominal power of ca. 100 W. A prototype of the proposed converter has reached a global efficiency above 92%, with a power factor greater than 0.97 and total harmonic distortion of input current of ca. 20%, along with total compliance with the power quality parameters imposed by national and international standards. The design of this converter also permitted the elimination of the electrolytic capacitors from within the power circuitry of the prototype through capacitance reduction; only metalized film capacitors were employed, contributing to enhance the lifespan of the converter, making it compatible with the lifespan of the LEDs being driven.