ANALYSIS OF LOW-FREQUENCY RIPPLE TRANSMISSION TO DCM OPERATING CONVERTERS FOR LED DRIVERS

This paper presents the analysis of the lowfrequency ripple transfer from the input voltage to the LEDs current of a DC-DC converter, in the buck, boost and buck-boost topologies operating in discontinuous conduction mode. This analysis fulfills the maximum limits recommended by IEEE Std. 1789-2015 to mitigate the effects of light flicker in humans. The objective is to find the maximum input voltage ripple percent values for a range of operation of each topology, in different LED loads. To do this, the mathematical models for each topology is applied in three LED loads, based on the dimensionless term low-frequency ripple transmission factor, that relates the percent ripple transmitted from Artigo submetido em 09/08/2019. Primeira revisão em 08/10/2019. Aceito para publicação em 24/03/2020 por recomendação do Editor Marcello Mezaroba. http://dx.doi.org/10.18618/REP.2020.1.0059 the input to the output of the stage. With these values, a study is performed to determine the minimum bus capacitance required for each case. The Luxeon 3014 LED is selected for simulations and implementations at three operating points of each topology, in prototypes with a rated power of 20W. The buck-boost topology stands out because it presents a low-frequency ripple transmission factor reduced and constant for the entire operating range.