Analysis and design of a boost-buck single stage topology for LED lighting applications

Light emitting diodes (LEDs) have great potential to replace existing light sources, like incandescent and fluorescent lamps due to their long life time and higher efficacy. Therefore, also the life time and efficiency of the LED-ballast are important factors in order to improve the overall system. In addition, size and costs are a relevant factor in the highly competitive LED market. With the benefits of low costs and size, single stage, single switch topologies are well suited in general lighting applications, providing at on the one hand a constant current for the LEDs while inherent shaping the input current for fulfilling EMI regulations on the other hand. This paper presents an analytical solution and the complete design of a boost-buck single stage, single switch topology for LED lamps. A prototype of a 12 W LED lamp verifies the analysis by experiment and shows a good performance at small size.