Comparison of single stage SEPIC and integrated SEPIC-Buck converter as off-line LED drivers

This paper presents comparison of single-stage Single Ended Primary Inductance Converter (SEPIC) and integrated SEPIC-Buck converter to drive Light Emitting Diodes (LED) in general lighting from a storage capacitance reduction point of view. Considering the low lifetime of electrolytic capacitors compared to that of LEDs, this study aims to compare which topology allows for using the smaller bus capacitance replacing it by a longer lifetime capacitor technology, increasing the overall system reliability. The analysis considers the same input/output parameters for both converters. The single-stage topology is a SEPIC operating in discontinuous conduction mode (DCM), which performs both power factor correction (PFC) and power control (PC) functions. In the integrated topology the PC stage is implemented by a Buck converter taking advantage of its output current source behavior, suitable for LED application. The design and implementation allows for a quantitative analysis between both topologies. The single-stage topology requires a 2.119 mF storage capacitance and achieves 85.12% efficiency, while the integrated topology requires a 187.5 μF storage capacitance and attains 83% efficiency for the same input/output parameters.