Acuity Brands
Provider Number J618
LED Light Quality: Achieving
Natural Dimming Performance
without Flicker
Course number AB516
Mark Phillips
1/19/15
Credit(s) earned on completion of
this course will be reported to AIA
CES for AIA members. Certificates
of Completion for both AIA members
and non-AIA members are available
upon request.
This course is registered with AIA
CES for continuing professional
education. As such, it does not
include content that may be deemed
or construed to be an approval or
endorsement by the AIA of any
material of construction or any
method or manner of
handling, using, distributing, or
dealing in any material or product.
______________________________________
Questions related to specific materials, methods,
and services will be addressed at the conclusion of
this presentation.
Copyright Materials
This presentation is protected by US and International
Copyright laws. Reproduction, distribution, display and
use of the presentation without written permission of the
speaker is prohibited.
© Acuity Brands 2015
Course
Description
LEDs have expanded the
possibilities in how we illuminate
building interiors and exteriors.
LEDs have brought a lexicon of new
terminology to the forefront. This
course will define LED Light Quality
and help you to recognize and
achieve high quality LED lighting
results on your next project.
Learning
Objectives
At the end of the this course, participants will be able to:
1.
Review the functions of components that make up an LED system
2.
Discover what characteristics of LED systems are required to achieve
natural dimming performance
3.
Learn about what technologies are used to dim LEDs
4.
Define flicker, its causes and effects, learn how to mitigate the effects
5.
Understand how to reduce LED anomalies and assure desired
performance.
What the heck
is that?





Flicker vs Continuous
Shimmer vs Smoothness
“Steppy” vs High Resolution
Color Shift vs Maintaining Color
Expected Light Level vs Full Range
(0-100%)
LED Systems
Dimmer
input
0-10V
DMX/RDM
DALI
Wireless
Forward Phase
Reverse Phase
OR
LED Driver
response
Current Reduction (CCR)
Pulse Width Mod. (PWM)
Hybrid Method
The driver delivers the desired
performance in the luminaire
LED
Light source
Constant Voltage
Constant Current
e
e
Sending a signal to the driver
Not directly dimming the
LED


Not all dimmers are
created equal: some
have linear responses,
some have logarithmic
responses, and others
exist
The pairing of
complementary (linear
and log) curves
provides the most
natural experience of
dimming.
AC Input
+
Control
0-10V, DMX,
DALI...
Pulse Width
Modulation
(PWM)
Constant
Current
Reduction
(CCR)
Hybrid
The driver is similar to a fluorescent ballast but
will control an LED instead of a fluorescent tube

Constant LED
current, varying
LED on/off times
Good dimming
regulation at deep
dimming (same
current) levels
 Little color shift
X Potentially
undesirable
flicker, depending
on frequency

Varying LED current,
LED always on

No flicker
 Higher LED
efficacy at lower
dimming levels
X Poor dimming
regulation at deep
dimming (low
current) levels

•



Varying LED current,
duty cycle and
frequency
Best dimming regulation
at deep dimming levels
High frequency
operation)
 No flicker
 Dimming to dark
No color shift when
dimming
Se
Light level was not a concern of
incandescent dimming because it
dimmed to off
Square law dimming:
10% measured = 32% Perceived
5% measured = 22% Perceived
1% measured = 10% Perceived
0% measured = 0% Perceived
Shouldn’t this great technology we
have in LEDs meet, if not exceed, the
performance of older light sources?
Digital drivers will change currents and with that brightness
levels in digital steps
The human eye is extremely sensitive for brightness
changes at low light levels
An LED has a very ‘unforgiving’ diode characteristic: it
reacts immediately to any change in drive currents - no
‘damping’



To ensure a continuous perceived
change of brightness, the change
in intensity from setpoint 1 to
setpoint 2 should be less than 3%
dimming level
0.103%
0.1%
1 2 3
dimming setpoint


Digital drivers will change currents and with that
brightness levels in digital steps
An LED has a very ‘unforgiving’ diode characteristic: it
reacts immediately to any change in drive currents - no
‘damping’
To ensure a continuous perceived change of brightness
between minimum dimming level and 100%, a minimum of
65,536 steps (16 bit resolution) is needed.
Flicker, Why all the Buzz
Flicker is increasingly becoming a concern in the
lighting industry.

Potential flicker-induced problems :



Headaches, fatigue, blurred vision, eyestrain
Neurological problems, including epileptic
seizure and other biological effects
‘Unstable light output’ in video applications

Incandescent

HID

Fluorescent

And NOW LED

The U.S. Department of Energy (DOE)
defines flicker as a “variation of light
output over time”

Repetitive change in magnitude over time,
or modulation, of the luminous flux of a
light source

Every light source operating on an AC
source will have a modulated signal


Visible Flicker: Flicker that
is consciously perceivable
by a human viewer.
Invisible or Imperceptible
Flicker: Flicker that is not
consciously perceivable by
a human viewer

Stroboscopic: indirectly
perceivable
IESNA has defined
two metrics for
flicker:
 Percent flicker
 Flicker index
IES Metric
Average
Peak-to Peak
Amplitude
Shape
Duty Cycle
Frequency
Percent Flicker Yes
Yes
No
No
No
Flicker Index
Yes
Yes
Yes
No
Yes
IEEE PAR1789 states minimum frequency of 1.25 kHz with 100% flicker



3-70 Hz – Epileptic
Typical for dimmed LED today
Seizure risk
70-165 Hz – Migraine
Inducement risk
165-800 Hz - Visual
Impairment,
stroboscopic effects
Light Level
Percent Flicker
Min.
Modulation
Frequency
100%10%
10%-5%
<25%
<100%
>10 kHz
>10kHz
0.1%
Source: Assist Recommends…
100%
100%
>1000Hz
>1000Hz
Red=80% unacceptable
Yellow = 80% acceptable
White = imperceptible
1%

Requirements
1.
Raise your hand
2.
Shake your hand

Demand Flicker % and Flicker
Index





Review Samples with your flicker
checker
Get Active




Max Flicker Percentage – 40%
Max Flicker Index - .15
Frequency above 1.25 kHz
CALiPER
IESNA and CIE are considering developing
standards
IEEE creating recommended practices for
evaluating flicker risks
Minimize Flicker – Ambient and
Task

Hospitals, Schools, Clinics, Offices, Classroom
and Daycare

California Energy Commission (CEC)



Zhaga


Voluntary California Quality LightEmitting Diode (LED) Lamp Specification,
December 2012
Title 20
Book 1
EPA EnergyStar

Lamps and Luminaire specificaitons


A forward-looking standard developed to
reduce anomalies with LEDs and phase cut
dimmers
It contain design specs for LEDs, drivers,
engines, controls and test guidelines for
help determining compatibility


Ex. An SLL-7A compliant lamp and dimmer must
be used together, which will yield a compatible
solution
Released in mid-2013 and created for new
products, not existing equipment

Understand the application requirements and set an expectation
for the customer, natural dimming is possible if correct technology
is implemented

Know what components will make up your system (control, driver,
LED)

Consider the driver and its capabilities, know which type the fixture
manufacturer is using

Ask about its flicker percentage or index, know what perceived
light level it can dim down to and what the dimming resolution is

Ask the luminaire manufacturer for a driver that meets your
requirements
This concludes The American Institute of Architects
Continuing Education Systems Course
Provider number J618
ContinuingEducation@AcuityBrands.com
Thank you for your
attention!!!
Questions?