Feature Story
Minimizing Flicker in LED Lighting
Applications
Learn How Richtek LED Lighting Solutions Minimize LED Light Flicker
All light sources that ultimately derive their power from the AC mains are likely to flicker. LEDs are particularly worse compared to incandescent lamps because LEDs react quickly to current variation. Most flicker manifest itself as periodic light fluctuation at double the AC line frequency, but incompatibility between lamps and peripheral lighting components can cause random lower frequency flicker as well.
Although 100/120Hz flicker is not perceived
by most humans, it can still lead to
irritation and eye fatigue. Therefore
flicker is one of the key parameters
that need to be considered when it comes
to replacing traditional lights with
efficient, long lasting LED lighting.
Luminaire manufacturers are
eager to solve this problem to win more
customers switching to LED lamps. This
article explains LED flicker phenomena
in relation to driver topology and LED
characteristics and introduces several
Richtek solutions to minimize LED light
flicker.
Flicker Definition
Most often, flicker is calculated by
using the IES RP 16-10 standard method.
For periodic signals
the percent flicker is defined as:
A comparison between different light
sources reveals various flicker percentages.
But how much flicker is allowed?
At this moment, there are no standards
that define the maximum allowed flicker
for LED lamps. But many Luminaire manufacturers
define the percent of flicker to be
less than 30% in the 100Hz/120Hz range.
LED light luminance is directly related
to the current through the LED. To minimize
light flicker, the current variation
through the LED needs to be minimized
as well. It is important to realize
that LED driver topology together with
LED string characteristics play
an important role in the design of low
flicker LED lamps.
Richtek LED Lighting Solutions to Minimize Flicker
If high power
factor is required, a way to minimize
flicker is to increase the converter
output filter capacitance. However,
size and cost need to be considered.
One could also choose LEDs with
higher dynamic resistance, or operate
the LED “closer to the knee” which increases
dynamic resistance as well.
Verification Tool
This
tool is quite simple to build
from readily available components,
and is very useful for checking
the light variation of different
LED lighting applications.
Related Products:
PFC flyback topology:
RT7302,
PFC Buck topology:
RT8487,
Linear
topology:
RT7321 and PFC
MR-16 LED driver:
RT8479
New Products
RT7302
in SOP-8 w/ HV start-up
RT7304
in SOT-23-6 package
Quasi Resonant switching PSR flyback
controllers with
0.99
Power Factor, ideal for
T8,GU10,and
E27
(read more)
RT8487
in TSOT-23-6 package
*
RT8497
built-in 620V/1.8A MOSFET
*
BCM switching LED driver with PFC and
transformer free design
*Coming soon!