Metodologia de projeto de conversores integrados aplicando técnicas de redução de capacitâncias em drivers de LED

Abstract

This work presents a methodology for the design and analysis of integrated converters, using buck, boost and buck-boost topologies operating in discontinuous conduction mode, as power factor correction and power control stages in LED drivers. The objective is to define a design and analysis method, with an emphasis on capacitance reduction, taking into account current standards and recommendations. To make this possible, first the generic design of converters is presented, making it possible to design any combination of topologies. Afterwards, the lowfrequency ripple analysis for LED drivers is presented, which helps to mitigate the effects of flicker on observers. This analysis allowed the selection of converters and operating point with a view to minimizing the required bus capacitance. To verify the results, a luminaire composed of 3014 LEDs is used, with a rated power of 26.9 W, in which the boost converter in the power control stage is replaced by the buck-boost converter. This case achieves a reduction of almost 50 % in capacitance, but with a loss of more than 1.5 % in converter efficiency. Finally, the analysis of capacitance balances is proposed to transfer the low frequency ripple filtering to the output capacitor in converters operating at universal input voltage, based on the dynamic modeling of the power control stage. With a 75 W load composed of 2 Lumileds 1208 LEDs in series, the bus capacitance was reduced and the output capacitance increased, resulting in a reduction in capacitance volume of approximately 45 % in the driver.