توپولوژی مجتمع مبدل DC-DC برای سیستم روشنایی خیابان LED بر اساس محرک مدولار Integrated Topology of DC-DC Converter for LED Street Lighting System Based on Modular Drivers

I. INTRODUCTION UE to the incentive to reduce the electric energy consumption in the various classes of consumers, all forms of improve the energy efficiency of the electric and electronic equipment are important. In street lighting, the lamps based on light-emitting diodes (LEDs) technology [1]- [6] have been shown to be more efficient compared to the tradition high-pressure sodium (HPS) lamps, despite the still dominant use of HPS worldwide [7]. The power LEDs have reached luminous efficacy and lifetime higher than 200 lm/W and 60000 hours, respectively [8]. Moreover, the LEDs technology has no mercury in its composition. Therefore, the use of LEDs for street lighting lamps has proved to be a good alternative to save electric energy and it has been the goal of many researches [9]-[12]. The LED lamps are supplied by a circuitry known as driver, which must be able to process the electric energy from the line and supply the LEDs with a continuous current. The driver lifespan must be compatible with the LEDs so that the lamp does not lose one of its main features, the high lifetime [7], [9]. The main responsible for the low reliability of the drivers is the electrolytic capacitor, widely used in power electronics topologies. Such capacitor technology is responsible for about 50% of failures in switching power supplies [13]-[15], as well as presents a lifetime lower than the LEDs. The useful life of electrolytic capacitors is reduced by half if the operating temperature is increased by 10°C. Thus, with the natural heating of the LEDs, the lifetime of the electrolytic capacitor becomes the critical factor that determines the lifetime of the driver [16]. In order to improve the driver reliability, several works in the literature suggest the replacement of the electrolytic capacitors by film or polyester ones [16]-[19]. A LED driver is usually composed by two stages: Power Factor Correction (PFC) and Power Control (PC). Both of the stages are implemented by DC-DC converters. The converter used for PFC is responsible for the high power factor and meeting the IEC 61000-3-2 Class C standard regarding the current harmonics inject into the public supply system. The PC stage is responsible for the LED current control in order to provide a continuous current with a small ripple. Both PFC and PC stages have independent controlled switches and its command circuits, which increases the driver components number. Thus, some works have presented an alternative that integrates the PFC and PC stages, sharing the same controlled switch and its command circuit [19]-[21]. Therefore, the number of active switches and their command circuits are reduced, as well as the control complexity, but the switch voltage and/or current stresses are increased. Besides a common node, the integrated converters must operate at the same switching frequency and duty cycle.