Analysis and design of LLC ballast in Gm mode for photovoltaic energy backup LED streetlight

A way to describe the LLC ballast in tranconductance G_m mode for current conversion to drive LED streetlight is proposed. On G_m description, the load response can be clearly observed in Region 2 since the transfer curves can be expanded outward as per the increase of the quality factor, and no curves huddled; in contrast, it is difficult to obviously view the load behavior in that region by using voltage gain G description. Moreover, a photovoltaic (PV) energy backup formed by lead-acid battery set is equipped using pulse charge through a boost converter with an incremental-conductance (INC) maximum power point tracking (MPPT). Analysis and modeling of LLC ballast to drive LEDs in G_m mode are explored. The sinusoidal-like full-wave ripple current for LED drives can be easily regulated to almost smooth by a small film capacitor instead of electrolytic capacitor. Microchip processor is employed to digitize whole control of the proposed LLC ballast. A prototype of scale-down 50-W LLC ballast to drive a dimmable LED streetlight is realized and verified by elaborate experiment.