Integrated SEPIC Buck-Boost Converter as an Off-line LED Driver without Electrolytic Capacitors

In this work, a new topology of integrated converter is proposed to be used as an off-line LED driver. The two stages of the converter are made up by a front-end SEPIC power factor corrector and a buck-boost converter for current regulation, both stages sharing the same power switch. It is demonstrated that when both stages work in DCM, less low-frequency ripple is transmitted from the bus capacitor to the output, allowing decreasing the amount of filtering needed and eliminating electrolytic capacitors from the power circuitry. Photometric data is used to size the maximum current ripple permissible at the LEDs, further optimizing filtering requirements and reducing capacitances to the maximum.