Analysis and design considerations of two-stage AC-DC LED driver without electrolytic capacitor

LED is widely used for lighting because of its high luminous efficiency and long lifetime. However, the lifetime of LED driver is much more limited due to the electrolytic capacitor, which is a key component in AC-DC LED drivers. Thus, as the storage capacitor, film capacitor will be more appropriate than electrolytic capacitor for a long lifetime LED driver. A cascaded two-stage converter with power decoupling is proposed in this paper to eliminate the electrolytic capacitor. The bus voltage ripple is intentionally enlarged to decrease the required capacitance so that a film capacitor can be used. The detailed design procedure will be given in this paper. A 0.7A/20W prototype has been built to verify the design.