IEEE Power Electronics Magazine - September 2014 - 18
Designing to Mitigate
the Effects of Flicker
in LED Lighting
Reducing risks to health and safety
by Brad Lehman and Arnold J. Wilkins
H
ow often has this scenario happened? You are
driving at night behind a car that has bright lightemitting diode (LED) taillights. When looking
directly at the taillights, the light is not blurry,
but when glancing at other objects, a trail of
lights appears, known as a phantom array. The reason for
this trail of lights might not be what you expected: it is not
due to glare, degradation of eyesight, or astigmatism. The culprit may be the flickering of the LED lights caused by pulse-
Digital Object Identifier 10.1109/MPEL.2014.2330442
Date of publication: 5 September 2014
width modulating (PWM) drive circuitry. Actually, many LED
taillights flicker on and off at frequencies between 200 and
500 Hz, which is too fast to notice when the eye is not in rapid
motion. However, during a rapid eye movement (saccade),
the images of the LED lights appear in different positions on
the retina, causing a trail of images to be perceived (Figure 1).
This disturbance of vision may not occur with all LED taillights because some taillights keep a constant current
through the LEDs. However, when there is a PWM current
through the LEDs, the biological effect of the light flicker may
become noticeable during the eye saccade.
BACKGROUND IMAGE LICENSED BY INGRAM PUBLISHING.
LIGHTBULBS ARE COURTESY OF BRAD LEHMAN
18
IEEE POWER ELECTRONICS MAGAZINE
September 2014
2329-9207/14©2014IEEE
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