1. A NEW CONTROL METHOD OF INTERLEAVED SINGLE-STAGE FLY
BACK AC–DC CONVERTER FOR OUTDOOR LED LIGHTING SYSTEMS
ABSTRACT:
In outdoor light-emitting diode (LED) lighting systems, there are a lot of applications. Depending on
the output power rating, the power stage to drive an LED can be classified into single-stage and two-stage
structures. The single-stage structure is for low-power LED lighting applications. However, it is difficult to
apply at over 60-70 W of output power because of its low efficiency and huge transformer at high power. On
the other hand, the two-stage structure is usually used for high power applications. However, it is
undesirable to cover wide output power range because of its poor power factor (PF) under the light load
condition. To solve these problems, this paper proposes a new pulse duty cycle control method with pulse
frequency modulation for an interleaved single-stage flyback ac-dc converter. The proposed converter
provides high efficiency under heavy loads with low ac line condition and under light loads with high ac line
condition. In addition, the proposed converter shows high PF and low total harmonic distortion even when
the output power is very low. As a result, a single LED ac-dc converter can cover wide power range for
outdoor LED lighting applications. To verify the validity of the proposed converter, an 81-W prototype
converter has been implemented and experimented on.