Analysis of series-resonant LED driver applied to reduce the low-frequency current ripple transmission

Abstract

The use of series-resonant converters (SRC) in light emitting diodes (LEDs) drivers has increased due to its simplicity and high efficiency. Furthermore, the use of SRC provides a reduction of the low frequency (LF) ripple in the LEDs' current, originated by the voltage ripple in the output of the power factor correction (PFC) stage (bus voltage ripple). Thus, the attenuation of the ripple transmission from the bus voltage to the LEDs' current achieve some desired features: (1) reduction of the bulk capacitance used at the output of the PFC stage, enabling the employment of long-life film capacitors, and (2) increasing the efficiency of the LED driver due to the low switching losses of the series-resonant converter. This work proposes an analysis of the SRC aiming to define a design methodology to improve the LEDs current ripple reduction provided by the SRC. Moreover, the work presents a discussion about the main factors that have influence in the ripple reduction and the limits for this attenuation, which has not been explored in the literature yet. Experimental results employing the SRC to supply a 10 Watts LED lamp are presented, validating the feasibility of the employed methodology and the proposed analysis.