A long lifetime passive LED driver with power factor correction

Abstract

In this paper, a novel single stage passive ac to dc converter is first proposed for LED drivers. No controlled active switch, electrolytic capacitors and auxiliary power supply are required in the proposed LED driver. The advantages of the proposed driver include long lifetime, high efficiency and recyclability. In addition, application of the proposed quasi-resonant circuit enables one to use much smaller capacitance and inductance for the capacitors and inductor to achieve high power factor and compact size. Theoretical analysis of the proposed LED driver is made, and some design guidelines are provided. Finally, a prototype system of 50-W rating is constructed. Experimental results confirm the validity of the proposed LED driver. It can be seen that the proposed driver is robust to variations of input voltage, frequency and output load. The features of low cost, long lifetime, robustness and without EMI problem render the proposed driver a very attractive alternative for outdoor applications.During this mode, diode D 2 is turned on and i L1 and i Ls continue to supply energy to the output load and discharge C 1 . The corresponding equivalent circuit is shown in Figure 5d. This mode will continue until v C1 reaches 0 and diode D 2 is turned off. Figure 5. Equivalent circuits of four operating modes in the positive half period of input ac voltage. (a) Mode 1 (b) Mode 2 (c) Mode 3 (d) Mode 4.