An Interleaved Single-Stage Flyback AC-DC Converter with Wide Output Power Range for Outdoor LED Lighting System

Abstract

In outdoor light emitting diode (LED) lighting system, there are a lot of applications. Depending on the output power rating, the power stage to drive LED can be classified into single-stage and two-stage structures. The single-stage structure is for low power LED lighting applications and it is hard to apply over 60~70 W output power because of its low efficiency and huge size of transformer at high power. On the other hand, the two-stage structure is usually used for high power applications and it is undesirable to cover wide output power range because of poor power factor (PF) at light load condition. To solve these problems, this paper proposes an interleaved single-stage flyback AC-DC converter with turn-on time mapped frequency control method. The proposed converter provides high efficiency at heavy load with low AC line and at light load with high AC line conditions. Also the proposed converter shows high PF and low total harmonic distortion (THD) even if the output power is very low. As a result, a single LED AC-DC converter can cover wide power range of outdoor LED lighting applications. To verify the validity of the proposed converter, an 81 W prototype converter has been constructed and experimented.