Today, lighting applications consume enormous portion of the electrical energy. According to the statistics provided by International Energy Agency (IEA), about 20% of the electrical energy utilization in the world is associated with lighting. Thus, any saving action in lighting section results in considerable lower energy consumption and consequently, lower cost. Obviously, using optimal light sources enhances the achievement of this goal. Technology improvements has introduced different light sources into the market. However, Light Emitting Diodes (LEDs) are the most recent ones. Due to the advantages of these lamps including high luminous efficacy, long lifetime, being toxic free, low ultraviolet emission, high color diversity and small sizes, LEDs are recently utilized vastly in lighting devices. However, in order to utilize these lamps, a driver is needed to provide their power from the AC mains. Also, because of increasing employment of LEDs, it is essential for the drivers to have an appropriate power factor. LED drivers should have some desired properties including output current regulation, high power factor, long lifetime, low cost and high efficiency. Therefore, many converter topologies as power factor correction (PFC) LED driver are presented. Also, major research is pursued to increase their efficiency and lifetime. But, surveying the existing drivers shows that this subject requires further investigation in order to increase the efficiency and decrease the complexity of the LED drivers in low power applications. The goal of this thesis is first the review of existing LED drivers with single stage PFC structure and then proposing new topologies with long lifetime and low losses. Therefore, in this thesis two new single stage single switch PFC LED drivers without electrolytic capacitors are proposed which enjoy from high efficiencies by using soft switching techniques. In the proposed drivers, the bulk capacitors have low capacitances and high voltage ripples to keep the balance between variable input power and constant output power. Therefore, the film capacitors can be used as the bulk capacitors which extends the drivers lifetime. The proposed drivers are analyzed theoretically and their performances are investigated. Also, the simulation and experimental results of prototype drivers for supplying a 21 W LED module justify the theoretical analyses. Keywords LED Driver, Single Stage Power Factor Correction, Without Electrolytic Capacitors, Soft Switching Techniques
