New-Tech Europe Magazine | July 2016 | Digital edition

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 1. Simplified Block Diagram of the LF77944 LED Driver.

Figure 2. 12-W LED Downlight Application with FL77944.

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