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Figure 1. Simplified Block Diagram of the LF77944 LED Driver.
Flicker Specs and
Solutions
The basic solution to the often
disturbing flicker effect is to keep LEDs
excited during the AC line voltage
drops. This seems like an easy enough
remedy. But the practical solutions
can be problematic. Thus, up to now,
DACD suppliers have used traditional
approaches of energy storage to
keep the LEDs excited. While this
basically solves the flicker effect, it
also causes distortion to the input line
current waveform. This impacts the
power factor (PF) and total harmonic
distortion (THD) performance of those
LED lighting systems.
This is a particular problem in those
industrial and commercial light-
ing products that have to meet the
accepted guidelines for PF and THD
performance. Typical specifications
require a PF of 0.9 or great-er. THD
Figure 2.
12-W LED
Downlight
Application
with FL77944.
New-Tech Magazine Europe l 31