Analysis and Design of High Power Factor LED Drivers without Electrolytic Capacitor

Abstract

With superior longevity, approximately 5 times that of compact fluorescents (CFLs), and high efficacy, around 1.5 times that of CFLs, LEDs are now attracting vast attention from both academic and industrial sectors. Unfortunately, current power supply drivers for LEDs have the following drawbacks: (1) for a two-stage configuration, the power factor correction (PFC) circuit can help LEDs achieve good operating performance but contain too many components and are large in size, have low efficiency and relatively high cost; (2) a single-stage configuration can perform well in PFC and efficiency, however reliability issues occur due to the use of the electrolytic capacitor. In this thesis, the theoretical analysis and implementation of two high power factor, soft-switched, electrolytic-capacitor-less LED drivers are presented. The two drivers solve the aforementioned issues while minimizing its size and cost. The detailed theoretical analysis illustrates the advantages of the presented circuits and provides insight into their design and operation. The simulated and experimental implementations verified the performance of both circuits, which achieve a high power factor, indicating that the drivers have good operating performance. Elimination of the electrolytic capacitors improves the LED drivers’ reliability. In addition, with the help of soft-switching capability, high efficiency is achieved. Simulation and experimental results are presented to support all merits of the two circuits.