Retificador de alto fator de potência e reduzido filtro de modo diferencial para alimentação de leds baseado na topologia SEPIC isolada com magnéticos integrados

Abstract

This work presents a proposition for feeding of LEDs by using an isolated and single-staged off-line driver, based on the SEPIC converter with coupled inductors working on discontinuous conduction mode (DCM). The chosen topology allows the reduction of the high frequency harmonic content of the input current adjusting the parameters of the coupled inductors (a technique known as ripple steering), which the benefits is the reduction of the inductance and volume of the differential mode EMI filter. Another benefit of the applied technique is the possibility of integrating the coupled inductors and the isolating transformer in a single magnetic, which contributes to a converter with smaller number of components, making it an alternative with number of components similar to a flyback converter, considered an industry design standard for single-stage and isolated drivers. Regarding the flyback, the chosen topology allowed a theoretical reduction of 7.61 times of the inductance of differential mode filter. A new magnetic structure was specially developed for this work in order to make the implementation of the converter prototype possible. Besides the analytical modelling of the converter and the new magnetic structure, some simulation techniques were also used, such as, the FEM (Finite Element Method) and the SPICE (Simulation Program with Integrated Circuit Emphasis). Finally, a prototype for open loop driving of a 50 W street light fixture from an effective 220 V grid is presented. The experimental results show that the prototype features high power factor (0.978), high efficiency (93%), low total harmonic distortion (4.7%), full compliance with minimum requirements of IEC 61000-3-2 class C and partial compliance with EN55015..