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This paper presents a multifunctional bidirectional converter applied to street lighting and photovoltaic (PV) microgeneration systems. The proposed converter works as an electronic driver supplying a street lighting luminaire based on Light Emitting Diodes (LEDs) at night, from AC single-phase mains with high power factor and reduced harmonic distortion. During daylight hours, the converter injects the produced energy by a PV panel to the grid, working as a grid-tie inverter. The proposed topology is based on the integration of two Flyback converters, one for each half-cycle of the grid voltage, avoiding the usual diode bridge rectifier for LED lamps drives, thus providing a bidirectional power flow. A prototype of the proposed electronic stage has been designed, built and tested, in order to validate the system. Finally, experimental results are presented. In rectifier mode, an efficiency of 86% was achieved, while an efficiency of 89% was obtained in inverter mode.

The use of series-resonant converters (SRCs) in light-emitting diode (LED) drivers has increased due to its simplicity and high efficiency. Furthermore, the use of a SRC provides reduction of the low-frequency ripple in the LED current, originated by the bus voltage ripple. Thus, an analysis of the SRC aiming to define a design methodology to improve the current ripple reduction provided by the SRC is proposed. Moreover, a discussion about the main factors that have influenced ripple reduction and the limits for this attenuation is presented, which have not been explored in the literature hither to.Introduction: Light-emitting diode (LED) current low-frequency (LF) ripple is a limiting factor for LED lighting systems [1,2]. Pulsating current might influence the performance of LEDs, such as maximum current limitation, efficacy, reliability, lifetime and optical performance, as flicker and chromaticity shift [2]. The LF ripple may also have an influence on the electronic driver design, especially in avoiding the use of electrolytic capacitors [1-4]. Thus, the reduction of LED LF current ripple is a relevant research topic.The use of a series-resonant converter as a power control (PC) stage for LED drivers is a good alternative to reduce the current ripple, besides providing simplicity and high efficiency for the system [1]. However, no previous work in the literature has performed an analysis about the factors that have influenced SRC LF current ripple reduction. Moreover, no study presented the limit of this ripple attenuation, or proposed a methodology for SRC design aiming at current ripple reduction. Therefore, this Letter proposes a SRC design methodology that analyses the main factors that have influenced LF current ripple, and defines the maximum ripple reduction provided by a SRC, which are completely new to the literature.

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