Among light sources, Light Emitting Diodes (LEDs) have better luminous efficacy. These sources, convert more than 20% of electrical energy to light energy which is much better than other light sources. LED lamp requires a driver circuit to provide a constant DC current. Thus, it is necessary to develop proper DC/DC and AC/DC converters in order to decrease the costs and electrical losses of driver. In order to increase the efficiency, the switched mode converters are used for these applications. In low power applications, in order to reduce complexity and cost, self-oscillating converters are applied. Control circuit of these converters is simple and usually is not separate from power circuit and uses power circuit voltages to provide proper control signal for power switch. In this thesis, first, all conventional methods to design a self-oscillating LED driver and their applications are discussed. Then, two new self-oscillating converters as LED driver are introduced. The first converter provides constant output current and thus, it is an appropriate solution for driving LED strings. This converter provides self-oscillation condition with low number of additional elements resulting in robustness, low cost and high efficiency. In second proposed structure, a new self-oscillating single soft-switched converter with resonant gate driver for driving multiple LED strings is presented. This converter is applied to drive high-power multiple LED string lights, and experimental results verify that in these conditions, the efficiency is about 92%. This converter provides the self-oscillation condition without any additional transistors or diodes. Also, the simulation and experimental results of prototype drivers are presented to justify the theoretical analyses. Keywords elf-oscillating, LED driver, dc–dc converter, soft switching.
