Saturday, October 12, 2013
The Crazy World of
LED’s and How to
Control Them
James R Benya, PE,
FIES, FIALD
Benya Burnett
Consultancy
Davis, CA
Continuing Education Credits
NECA has been accredited as an Authorized
Provider by the International Association for
Continuing Education and Training (IACET) and is
authorized to offer IACET CEUs for its programs that
qualify under the ANSI/IACET Standard.
This session is eligible for 0.2 IACET CEUs
To earn these credits you must:
• Have your badge scanned at the door
• Attend 90% of this presentation
• Fill out the online evaluation for this session
2
Learning Objectives
• Important understanding of how LED’s are made
and how they work
• Critical understanding of how LED color,
dimming, flicker and control issues
• Clear understanding of capabilities, issues and
options of LED’s used as directional lighting
• Clear understanding of capabilities, issues and
options of LED’s used as linear display lighting
The lighting industry used to be a plodding business, slow to change and with rare new
technologies. But no longer! Solid state lighting, principally light emitting diodes, have
totally revolutionized lighting. LED lighting fixtures, LED replacement lamps, and all
kinds of special new products are part of lighting today. And with them has come a
revolution in lighting controls, with wireless controls, network controls, and everything is
dimmable – if you can get it to work.
This workshop will explain how to plan, install and troubleshoot LED control devices
and systems. It will include dimmers, switches, sensors, small systems, large systems,
networked controls, wireless controls, and the world of drivers, dimmers, and other
components now part of everyday LED installations. It will include teaching how to
stay current, where to get more education, and how to get assistance from
manufacturers, agents and other resources, especially when things aren’t working the
way they were planned. The program will include troubleshooting and fixes for common
LED lighting system control issues. Breakout sessions will allow groups to identify and
discuss particular problems.
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Saturday, October 12, 2013
Please note
• This program is intended for a wide
audience
• Many of you will find portions to repeat
things you already know
• Don’t worry – there is some new stuff in
here for everyone
LED Anatomy
PART ONE
What is Solid State Lighting (SSL) and How is it
Fundamentally Different?
Conventional Lighting
Generates light by either
• Incandescence (heating)
• Low intensity mercury
discharge
• High intensity mercury
discharge
• Fluorescence (phosphor
conversion of discharge
spectrum) to create white
light or to improve color
LED
• Generates a specific
narrow band of colored
light by passing DC
current through a diode
• Fluorescence or
combinations of R, G, B
(and other colors) to
create white light
Brief History of SSL
Year
Event
1962
First visible light LED (red)
Through 1990
Evolution of red, orange and yellow LED mostly for indicator lights and similar low wattage
applications, based largely on gallium arsenic and gallium phosphorus
1992
Development of Indium Gallium Nitride technology, allowing for short wavelength LED
1995
High Brightness Blue LED and Green LED (Shuji Nakamura)
1996
White LED using RGB
1997
White LED using phosphor coating
2000
Commercially viable white LED, 10 lumens per watt
2010
Commercially viable white LED, >100 lumens per watt, wide choice of color temperatures and
CRI values
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Saturday, October 12, 2013
Evolution of LED
What is a DIODE?
200
• Electronic device
• Allows electricity to pass one direction, not
the other
• Used to rectify AC electricity to DC
>150 lm/W
First > 100 lm/W Red
Native Substrate
100
Shaped AlInGaP/GaP
Red-Orange-Yellow
Fluorescent Lamp
Green
Transparent Substrate AlInGaP/GaP
Red-Orange-Yellow
Unfiltered Incandescent Lamp
Yellow Filtered Incandescent
Lamp
Luminous Efficacy (lm/W)
10
AlGaAs/AlGaAs
Red
Red Filtered Incandescent
Lamp
GaAsP:N
Red-Orange-Yellow
Edison’s First Light
Bulb
1
Holonyak’s First
Commercial LED
White
AlInGaP/GaAs
Red-Orange-Yellow
Blue
AlGaAs/GaAs
Red
– Power supplies
– Radio circuits
InGaN
GaP:N Green
GaP:Zn,O
Red
• Specific types emit light when this
happens.
SiC
GaAsP
Red
Ga0.6As0.4P
Red
0.1
1960
1970
1980
1990
2000
2010
Dupuis and Krames, IEEE J. Lightwave Tech. 26, 1154 (2009).
Real Diode
Forward Voltage
Real Diode
• Some forward resistance
• Almost infinite backward resistance
• Won’t conduct forward current until a
minimum voltage is achieved
– LED 1.8 to 3.1 volts
+
+
Battery or
DC power
supply
-
V
Current flow
Current flow = ∞ if V > Vf
Current flow = 0 otherwise
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Saturday, October 12, 2013
Real Circuit
Forward Voltage
Parallel Diode Circuit
Forward Voltage
I = (V-Vf)/R
Pdiode = I x Vf
Presistor = I2 x R
I = (V-Vf)/(R/3)
Pdiode = (I/3) x Vf
Presistor = (I/3)2 x R
+
+
Battery or
DC power
supply
-
Resistor in
ohms
R
V
+
+
+
-
-
-
+
Battery or
DC power
supply
V
Current flow ~ (V-Vf)/R if V > Vf
Current flow = 0 otherwise
Parallel Circuit
Resistor in
ohms
Series Diode Circuit
Forward Voltage
• Divide the amps among the diodes
– Less amps per diode means less power per
diode
– Three diodes do the work of one
– Each runs cooler
– Heat can be spread out
• Very Low Voltage (like 2-3 volts) means
heavy gauge wires
R
Current flow ~ (V-Vf)/R if V > Vf
Current flow = 0 otherwise
I = (V-3Vf)/R
Pdiode = I x Vf
Presistor = I2 x R
+
+
Battery or
DC power
supply
-
V
Resistor in
ohms
Current flow ~ (V-3Vf)/R if V > 3Vf
Current flow = 0 otherwise
R
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Saturday, October 12, 2013
Series Circuit
•
•
•
•
•
•
Increase the voltage, drop the amps
Divide the power among the diodes
Each diode operates at less amps
Diodes operate cooler
Distribute heat more evenly
Higher voltage means smaller gauge wires
Series Parallel Diode Circuit
Forward Voltage I = 2(V-3V )/R
f
Pdiode = I/2 x Vf
Presistor = (I/2)2 x R
+
+
Battery or
DC power
supply
V
Resistor in
ohms
Current flow ~ (V-3Vf)/R if V > 3Vf
Current flow = 0 otherwise
R
Series Parallel Circuit
• Increase the voltage, drop the amps
• Increase total output by adding series
groups
• Best of both worlds
The Ideal LED for lighting is
often a point source.
Making a number of LED’s
appear as a point source is
a challenge.
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Saturday, October 12, 2013
Real Circuit
Forward Voltage
AC with LED
I = (V-Vf)/R
Pdiode = I x Vf
Presistor = I2 x R
+
Current and light
“pulse” – creating
flicker or
“shimmer”
-
Battery or
DC power
supply
+
+
Vf for most LED’s
is around 2.5 volts
-
V
-
Resistor in
ohms
Current flow ~ (V-Vf)/R if V > Vf
Current flow = 0 otherwise
R
Pulse Width Dimming
Voltage Dimming
BRIGHT
+
Jittery behavior as V
approaches Vf then
it stops abruptly
DIM
Very fast
switch
+
Battery or
DC power
supply
-
Efficiency drops as
voltage goes up
Color changes as
current goes up
Battery or
DC power
supply
+
+
-
Good behavior to
below ~1% light
Efficiency constant
Color constant
Flicker free
Flicker increases as
light dims
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Saturday, October 12, 2013
Constant Voltage Systems
Pros
• Simple
• Low cost
• Easy to wire
• Secondary side dimming
and/or color changing
with PWM
• Keep adding diodes in
parallel (or series parallel)
to capacity of circuit
Cons
• Challenging performance
at the low end of dimming
• Dimming flicker
• Less efficient
Integrated Power Supply/driver
Ballast-like product
• Plenty of room
• Cool enclosure
• Removed from lamp
heat source
Lamp Integrated
• Not much room
• Hot location
Constant Current Systems
Pros
• Better dimming
performance
• Reduced dimming flicker
• More efficient
Cons
• Hard to wire (series
circuit)
• To add diodes, add in
series –limited ability due
to voltage climb
• More expensive
Dimming Notes
• Non dimming LED systems are easy and
inexpensive
• Dimming LED systems are complicated
and not easily driven by phase cut
dimmers
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Saturday, October 12, 2013
Product Development Notes
• LED arrays today are usually series parallel
• There is a push to increase acceptable LED
system voltage
– More devices in series, lower current
– Larger lumen packages
• There is a push to make the building systems
responsible for providing DC power
Heat
Other light sources
• Radiant heat (IR)
• Conducted heat through
the socket
• Convected heat through
the ambient air
LED
• Conducted heat through
the socket or surrounding
structure
– Makes LED systems appear more energy
efficient
Parts of an LED
LED Fabrication
LUXEON Rebel
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Saturday, October 12, 2013
Die Shape and Light Extraction
(Al,Ga)InP + window layer
wb pad
(Al,Ga)InP
GaAs
DBR
GaAs
(a) Thin AS
(b) Thick AS
GaAs
(c) Thick AS + DBR
p-GaP
n-GaP
substrate
host
substrate
metal
n-GaP substrate
p-GaP
(d) Thick TS
(e) Shaped TS
(f) Thick RS
InGaN-GaN-Al2O3
Basic Commercial LED Package
100
Light
Extraction
(%)
Light
extractionEfficiency,
efficiency, C ext
ext (%)
(Al,Ga)InP-GaAs or GaP
90
TFFC
80
CC(PS/ITO)
low power
VTF
70
Shaped TS
60
CC (PS)
Thick RS
50
CC (PS/ITO)
high power
FC (Al)
40
Improved TS
30
CC
TS
20
10
FC (Ag)
Thick AS + DBR
Thick AS
Thin AS
into silicone or epoxy (n ~ 1.5)
0
p-spreader
p-wb pad
1990
1995
2000
2005
2010
p-type
Al 2O3
n-type
n-type
n-wb pad
Al 2O3
n contact
p-type
(a) Conventional Chip - CC
(b) Flip Chip - FC
reflective
p contact
Year
Year
after Krames et al., IEEE J. Display Technology 3, 160 (2007)
n-wb pad
light extraction
features
n-type
p-type
host
substrate
reflective
metal bond
n contact
n-type
p-type
reflective
p contact
(c) Vertical Thin Film - VTF
(d) Thin Film Flip Chip - TFFC
Commercial Multi-die Arrays
Phosphor-based White LEDs
Cree
Lumileds
• Blue LED + Y3Al5O12:Ce3+ (“YAG”)
– Efficient use of blue pump light
– Limited to ~ 4000-10000K
– CRI < 80 typically
– Currently, >> 100 lm/W @6500K
– “Valley of Cyan” 490-515 nm
– Limited red
From Soraa, after Krames et al., IEEE J. Display Technology 3, 160 (2007)
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Saturday, October 12, 2013
Where is the phosphor?
Hot Phosphor vs Cold Phosphor
a. Hot phosphor, in direct contact with LED
b. Cold phosphor, physical distance from
LED
Diffuser or
optical
lens
White LED or Mixture of
White and other colors
Phosphor
Coated
lens
UV, Violet, Blue or Green LED
Luger Research. eU
Making LED products
Most important in order
1. Thermal management
2. LED quality
–
–
Color rendering
CCT
3. Optics
4. Driver quality
–
–
–
–
Reliability
Flicker control
Dimming
Power quality
Parts of a “point source” LED Luminaire
•
•
•
•
•
•
Electrical connection
Driver
LED
Phosphor
Optic
Housing
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Saturday, October 12, 2013
Light Engines
Parts of a point-source LED replacement lamp
• A single apparent “lamp” by traditional
standards
• Inside:
– Driver
– LED
– Phosphor
– Optic
– Electrical connections
Standardize LED luminaires
• Standard thermal interface
• Standard electrical interface
• Flexible choice of LED and optic
• Flexible choice of driver
• Flexible design of heat sink and housing
Linear LED Luminaires
• Alternative to fluorescent fixtures
• Distributed heat allows small form factor in
low wattage systems
GE
Cooper Io
WAC
Color Kinetics
Fraqtir
11
Saturday, October 12, 2013
White LED
Color Rendering Index
• What color temperature of white?
2700K
3500K
Kruithof’s curve, 1941,
Philips
Partially reaffirmed 2009
by Vienot, Durand and
Mahler (Fr) with “low CCT
most preferred at 150,
300 or 600 lux”.
Matches the McCandless
Method (“fill warm, key
cool”)
Color Quality for White LED
• Lower efficacy
• Higher CRI and improved R9-R15
70 CRI
90 CRI
Cree
Color Quality
3000K
Ra = 80 (CRI)
R9= 19
3000K
Ra = 98 (CRI)
R9 = 98
Xicato XSM
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Saturday, October 12, 2013
Studying Product Data
Color Summary
• Choose correlated color temperature
– 2700K, 3000K, 3500K, 4000K, or 5000K
• Choose color quality
– CRI + R9
– Other metrics (CQS, etc.)
• Choose color consistency (MacAdam
steps)
• Try to get a color warranty
Linear source applications
•
•
•
•
•
•
•
•
Display cases
Freezer cases
Coves and Valences
Shelf lighting
Undercabinet lighting
Inside cabinet lighting
Wallwashing
Wall grazing
Linear luminaires
• Distributed LED’s all along a linear
channel or tube
• Modular lengths allow increments of size
• Qualities of LED’s and drivers vary
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Saturday, October 12, 2013
Refrigerated cabinets
Cove luminaires
• Mostly indirect
ambient lighting
• Plug together
• Line voltage
integral driver
• 2700K, 3000K,
3500K, 4000K
• 80-83 CRI
• 350-700 lumens
per ft
Philips
GE
Undercabinet and Valences
Philips
• From 100 lumens per foot up to 700 lumens per foot
• 2700K, 3000K, 3500K, 4000K, 5000K
• Low voltage remote transformer or line voltage enclosed
luminaires
• Mostly 70-80 CRI
• Designed for vertical
and horizontal
mounting
• 250-500 lumens per
foot
• 3000K, 4000K and
5000K
• 75-80 CRI
• Remote DC power
supply (size
constraints)
GE
Tape light
• From 70 to 250
lumens per foot
• 2700K, 3000K,
4000K, 5000K and
6500K
• 70-82 CRI
• Remote power
supply
• Optional enclosures
and lenses
Edge Lighting
Elemental LED
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Saturday, October 12, 2013
Display Case Lighting
Wall Washing and Valences
GE
•
•
•
•
•
2 to 6 w/ft
150-500 lumens per ft
3000K, 4000K, 5000K, 6500K
80 CRI typical
Remote power supply
Sylvania, GE,
Lighting Science
Group
Wall Grazing
• Not wallwashing –
purposeful gradient
and revelation of
texture
• 700 lumens per
ft/14 watts/ft
• Integral line voltage
driver
• 2800K/80CRI
• Modular linear wallwash
• Symmetric and Asymmetric beams
• 300-600 lumens per foot/5-10 watts
per foot
• Integral 120-277 driver
• 2700K, 3000K, 4000K, 80CRI min
Backlighting
• Various LED lighting
systems designed to
illuminate the inside
of a light box
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Saturday, October 12, 2013
Dedicated LED Recessed Adjustable
Light Engines
Light engines* include
• Power unit and thermal
connector
• LED module
• Remote phosphor or
mixing lens (if used)
• Optic
*Zhaga is a standard for light
engines
• Light engine
(proprietary or
OEM product)
• Adjustable engine
holder and optic
• Driver usually
remote
USAI
Lucifer
Dedicated LED Multiples
• Several LED
luminaires – one
housing
• Recessed or
pendant
• Usually derived from
track heads
Amerlux
Dedicated Track Luminaires
• Optimized for
LED package
• Often for high
wattage (up to
about 50 w)
• Driver in
separate
compartment
RSA
Lightolie
r
Contech
Amerlux
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Saturday, October 12, 2013
Dedicated Semi-Theatrical Luminaires
• High power and high
precision applications
• Current products to
4500 lumens, >50
watts, 2700K, 3000K,
4000K
• Wide range of optics
• Some allow accessory
lenses
• CRI 80 to 98
Low Voltage Monopoints
• Monopoint
• Arm mount
• Rail mount
WAC Lighting
Lighting Services
Inc.
MP Lighting
Edge Lighting
Times Square
Wallwashers
• Monopoint
• Recessed
• Semirecessed
• Track
Replacement LED lamp products
• Install in existing
luminaires
• Install in new
luminaires
designed for
older technology
• Potential for
considerable
reduced cost
Edge Lighting
Fraqtir
17
Saturday, October 12, 2013
Replacement MR16
Replacement PAR38
• 15-20 watt class
• 2700K and 3000K
common
• 3500K and 4000K not
common
• Under $40 and falling
• 10 watt class
• 50 watt halogen
replacement (?)
• 2700K and
3000K common
• 3500K and
above
uncommon
Replacement GU10
LED Control Basics
• Another option
• 120 volt GU-10 base
• Same optics as the
low voltage lamp
LED
Lighting
Devices
“Driver”
Control
device
*Not always
Power
control
circuits
Line AC to
low voltage
DC rectifier
and filter
Dimming
Circuits*
Communications or power signaling
conversion circuits*
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Saturday, October 12, 2013
Line Voltage Switching
Wallbox
Dimmers
Dimmers of Various Types
• Standard forward phase cut
• Magnetic forward phase cut
• Electronic reverse phase cut
• CL rated phase cut
• Simple circuit
• Inrush to driver is an issue
LED replacement
lamp
OR
LED fixture with
dimmable driver
inside
OR
Incandescent
dimming module
in dimming
system
Line Voltage
Dimming
Line Voltage Dimming LED’s
• With wallbox triac dimmers for
incandescent lamps
– Most dimmable integrated replacement lamps
– Luminaires with forward phase-cut dimmable
drivers
– Some luminaires with integral transformers
and dimmable LED replacement low voltage
lamps
– Special transformers for dimming LED strips
and tape lights
Line voltage
dimmable driver
Dedicated LED
luminaire
OR
Low voltage
transformer
LED MR16
replacement lamp
OR
Dimmable
“transformer”
for LED
strips
Line Voltage Dimming LED’s
• With wallbox reverse phase cut dimmers
– Most dimmable integrated replacement lamps
– Luminaires with reverse phase-cut dimmable
drivers
– Some luminaires with integral electronic
transformers and dimmable LED replacement
low voltage lamps
19
Saturday, October 12, 2013
Line Voltage Dimming LED’s
Ten volt
Wallbox
Dimmers
Line voltage
dimmable
driver
• With CL rated phase cut dimmers
– Most dimmable integrated replacement lamps
– Luminaires with forward phase-cut dimmable
drivers
– Some luminaires with integral electronic
transformers and dimmable LED replacement
low voltage lamps
– Special transformers for dimming LED strip or
tape lights
0-10 Volt DC Dimming LED’s
Low
voltage
transformer
Ten Volt
Module on
Dimming
System
Ten Volt Dimming
Digital Signal
from DALI,
Ecosystem, or
other system
• Dimmer includes an on-off switch and 0-10
volt output
OR
• Dimming module has an on-off relay and 010 volt output
Ten Volthas a 0-10 volt line voltage
• Lighting system
Module on
dimming driver
Dimming
System
OR
• Lighting system has a transformer and a
separate low voltage dimming module
Low voltage
dimmer
Line voltage
digital driver
Low
voltage
transformer
Low voltage
dimmer
Ten Volt
Module on
Dimming
System
Digital Dimming
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Saturday, October 12, 2013
Digital Dimming LED’s
• Driver on fixture is a digital system driver
OR
• System dimming module has an on-off
relay and 0-10 volt output
When Dimming Goes Wrong
• Symptoms
– Dimming range too limited
– Lamps don’t work or strobe and flicker at any
setting
– Lamps strobe or flicker when dimmed
– Weird jumps, starts, etc.
– Noise, smoke or flames
Dimming and Flicker
• Investigate LED and dimmer interactions
• Evaluate flicker issues on display
When Dimming Goes Wrong
• General Solutions
– Make sure dimmer is not overloaded
• 600 watt dimmer use only 150 watts of LED’s
• Make sure transformers and components are
properly rated primary and secondary
– Check fixture or lamp manufacturer’s
compatible dimmer list
– Check wiring diagrams and wiring carefully.
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Saturday, October 12, 2013
When Dimming Goes Wrong
• Low voltage solutions
– Be sure dimmer or dimming module is rated
to match power supply
• Magnetic transformer = magnetic phase cut
dimmer
• Electronic “transformer” = reverse phase cut
dimmer or “CL” rated dimmer
– Try swapping out low voltage dimming
modules
– Check 0-10 volt drive circuit voltage
Final Comment - Flicker
• PWM dimming causes flicker that can be
detected by the naked eye
• Most constant voltage and low voltage
circuits flicker at 120 Hz
• Flicker cannot be easily mitigated without
higher frequency PWM
• Flicker is least likely in constant current
driver circuits
When Dimming Goes Wrong
• Line voltage solutions
– Try a stabilizing load
• Connect a 40 watt incandescent lamp across the
dimmer output, check to see if it dims and if that
makes the LED’s work better
– Add an incandescent load permanently to
stabilize the circuit
– Add a resistor module to stabilize the circuit
Electronic transformer and dimmer
0%
75%
25%
100%
50%
No Dimmer
22
Saturday, October 12, 2013
Thank you for attending
FINAL QUESTIONS
Please remember to
complete
the course evaluations.
Thank you.
23