ESTUDO DAS TOPOLOGIAS DE DRIVERS LED: análise de fatores que influenciam o tempo de vida útil e eficiência

Abstract

The LED systems are featured in the market, and its implementation for many applications presents challenges for manufacturers and product development. This work considers the importance that the LED driver has to ensure the reliability of a lighting system as a whole, being directly responsible for its life span and efficiency. In addition, this study begins by showing the theoretical concepts as junction p-n semiconductor heating, a mathematical relations defined by the equation of Shockley between current in the LED voltage and load variations. Next, will be explained what are the circuit blocks that make up a LED driver, with emphasis on conversion stage DC-DC, whose circuit is critical in determining the driver efficiency, power factor and product life span (due to electrolytic capacitors filtering). Then its presents in details the types of LED drivers on the market, especially as the topologies of voltage control and current load; in order to show the advantages and disadvantages of each one of them. Then, from this comparison, can be concluded that it is necessary detaiLED technical knowLEDge to select the one most appropriate topology for each specific application. As a practical study case, the concepts presented are exemplified through a comparative technical analysis of two LED Drivers engineering samples, one with constant voltage topology in charge (ELECPOWER 100-277VCA - 48VDC) and another with constant current (OSRAM OPTRONIC OT 9/10 24-350). In this analysis will be tested an electrical performance, a, thermal map of the most important components and an electrical circuit schematic. After that, some direct comparison between the two LED drivers made through lab tests. The results confirm and measure how some factors such as operating temperature and current load variations directly influence in the LED drivers life span, luminescence and efficiency. Finally, after analyzing the characteristics between the two topologies, the author concludes that the choice of a constant current topology, which had more precise current output control to the load, are recommended to use with recent technology of organic LEDs when applied to outdoor lighting. Also suggests that in a near future topologies of converters that allow the replacement of the electrolytic capacitor by a film capacitor will be predominant in the market, because will enable a large increase in the LED systems life span and efficiency.