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Solutions for Today’s Low-Power LED Lighting Trends
Brian Johnson, James Lee
Abstract: Why all the interest in LED lighting? The answers are
as individual as the LED lighting application. LED lighting is
discussed everywhere; at times, to the depth of the physics that
generates the photons or the science of creating an atmosphere
receptive for the users and the environment. LED lighting presents
an array of lighting choices through color, brightness, and ability to
mount in any shape or location. LED lighting pushes the bounds of
creativity by using lighting as the paint brush for expressing ideas.
LED lighting offers directional, controllable, changeable, and
architectural enhancement to the viewers’ quality of experience.
However, just as important as the quality of the experience; LED
lighting can save energy. The U.S. Department of Energy (DOE)
Solid-State Lighting (SSL) program leverages industry partners to
“spur SSL research, development, and communication. Solid-state
lighting (SSL) technology has the potential to cut U.S. lighting
energy usage by one-quarter and contribute significantly to our
nation's climate change solutions. The U.S. Department of Energy
acts as a catalyst to drive R&D breakthroughs in efficiency and
performance, and to equip buyers to successfully apply SSL
lighting.”[1] LED Lighting can create light comparable to
incandescent bulbs using up to 85% less energy and lasting up to 50
times longer.[2] Other added benefits from LED Lighting include
longer useful lifetimes, lower maintenance, no UV or IR radiation,
and no mercury content. SSL can potentially save 190
terawatt-hours of energy usage by 2030.[3]
This whitepaper examines LED lighting trends and Fairchild
solutions. LED lighting applications fall into three basic input
power levels: low-power is less than or up to 20 Watts; mid-power
is between 20 Watts and 50 Watts; and high-power is above 50
watts (see Fig. 1). In the real-world, applications do not always fit
nicely in these three buckets, but these power levels align when
considering LED driver solutions. LED applications are focused on
high-brightness LED designs.
This white paper explores low-power ≤20W applications,
especially bulb-type lamp replacements or retrofits, replacement of
existing lamps and fixtures, and new construction fixtures.
LOW-POWER LED LIGHTING TRENDS
The global sales of high-brightness LEDs was
estimated at $890 million in 2010 with a forecast
calculated annual growth rate of 39 % from 2010 to
2015.[4] The market potential is large and growing, but
challenges for the LED driver include efficacy
improvements (efficacy is the ratio of lumens per watt),
lowering the cost, and increasing operating lifetime.
The DOE SSL program predicts the potential of
high-brightness LEDs to exceed the conventional
technologies of today and the past. Fig. 2 and Fig. 3
show the trends of improving efficacy. Efficacy has
input power in the denominator of the metric, the input
power and the efficiency of delivering energy to the
LED string is related to the LED driver solution. One
single driver topology is not optimal across the full
range of LED power load possibilities, but there is a
minimal set of topology choices to consider that meet
the entire spectrum of LED driver development needs.
High Power (>50W)
Outdoor Lighting, Street light
Applications
HID Floodlight Replacement
HID Street Lighting Replacement
Middle Power (20 - 100W)
Indoor/Outdoor Lighting
Down Light, L-Light, Flat Light,
PAR Replacement, CFL Replacement, LFL Replacement
Low Power (1 - 20W)
Ornament/Interior Lighting
Light Strip, R-Lamp
Incandescent Replacement
Replacement of CFL Blub, MR Lamp and PAR
1
20
50
100
1000 (W)
Power Range
Fig. 1.
Three Basic Input Power Levels
© 2011 Fairchild Semiconductor
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Solutions for Today’s Low-Power LED Lighting Trends
Total cost of the lamp impacts what the end user sees
and becomes a frequent impediment to the adoption of
the LED light solutions, regardless of performance
improvements. A presentation at the DOE 2011
Solid-State Lighting Market Introduction Workshop
suggested the need for cost targets as shown in Fig. 5,
almost a 50 % reduction in cost every four years.[8] The
selection of the LED driver topology is important in
the end overall best cost solution.
Fig. 2.
Efficacy and Projections of Different Light Sources [5]
Fig. 3.
Recent LED Efficacy Performances [6]
Selecting the topology can be aided by selecting the
most efficient semiconductors, but the other common
design constraint is the cost of the driver. The DOE
SSL program approximates today’s costs as shown in
Fig. 4; the driver is 10% to 20% of the total
manufacturing cost.
Fig. 4.
Fig. 5.
Cost Reduction Targets[8]
Operating life is related to the reliability of the
power supply. Reliability is affected by component
count, types of components used, and temperature or
power dissipated in the LED driver design. Reliability
can be calculated using a part-count method with the
goal to reduce the number of components used in the
LED driver selection. Reliability is also affected by
operating temperature; so, while thermal design is
important, it is equally important to reduce the power
losses associated with LED driver components and
topology control method. The trend is to eliminate
components like electrolytic capacitors and
opto-isolators and integrate these features into the
control silicon.
Approximate Cost Proportions[7]
© 2011 Fairchild Semiconductor
2
Solutions for Today’s Low-Power LED Lighting Trends
I. STANDARDS & AGENCY REQUIREMENTS
There are many standards or agency programs for
regulation of LED drivers, including both voluntary
and mandatory programs. Table 1 is a sample of a few
agency programs for lighting.
TABLE 1. SAMPLE OF WORLDWIDE AGENCY PROGRAMS
Agency
Location
Voluntary vs.
Mandatory
Energy Star - US
United States
Voluntary
California Energy
Commission
United States California
Mandatory
European Commission
ErP Ecodesign
Directive
Europe
Mandatory
The list should include FCC requirement 47 CFR
part 15, Class A and Class B, Harmonic Emission
limits ANSI C82.77-2002 or IEC 61000-3-2, safety
standards UL 8750 or IEC 60650 Part 1, Line Transient
protection IEEE C62.41.1991, Class A. or Class A
audible noise. LM-80: specifies procedures for
determining lumen maintenance of the LEDs and LED
modules, not the luminaries. LM79 specifies
procedures for measuring luminous efficacy. TM-21
specifies the method to determine expected operating
life. Last, but not least, NEMA SSL 1 Electronic
Drivers for LED Devices Arrays or Systems.
While there is a lengthy list of applicable standards,
examining the Energy Star program requirements
highlights many of the LED driver design requirements
and is shown in Table 2. The items listed are focused
on the LED driver, not necessarily the lamp or fixture.
TABLE 2. LED DRIVER SPECIFIC STANDARD AND AGENCY REQUIREMENTS
Item
Power Factor
(PF)
Total Harmonic
Distortion (THD)
Dimming
Operating
Voltage
Reference
Energy Star Program Requirements for Solid-State Lighting Luminaires
Version 1.1 (Effective date: Feb 1, 2009)
≥ 0.7 (Residential)
≥ 0.9 (Commercial)
Energy Star Program Requirements Product Specifications for Luminaires
(Light Fixtures) Version 1.0, (Effective date: Oct 1, 2011)
Residential ≥ 0.7 for >5W
Commercial ≥ 0.9 for >5W
EN(IEC)61000-3-2 Class C (Lighting)
Class C (>25W) ≤ 30%THD
(3rd Harmonic)
Class D (≤25W)
KS C7651/2/3 (IEC61000-3-2)
Class C (>25W)
Class D (≤25W)
Energy Star Program Requirements Product Specifications for Luminaires
(Light Fixtures) Version 1.0, (Effective date: Oct 1, 2011)
Continuous dimming
from 35% to 100% of total
light output
NEMA SSL 1-2010
120, 127, 208, 220, 230,
240, 277, 347, 480 VAC at
50 or 60 Hz,
12 or 24VAC or VDC
Energy Star Program Requirements for Solid-State Lighting Luminaires
Version 1.1 (Effective date: Feb 1, 2009)
Off-state Power Zero
Exceptions for
“Controlled/Intelligent”
Luminaires <0.5W
Energy Star Program Requirements Product Specifications for Luminaires
(Light Fixtures) Version 1.0, (Effective date: Oct 1, 2011)
Off-State Power Zero
Exceptions for
“Controlled/Intelligent”
Luminaires <1.0W
Energy Star Program Requirements Product Specifications for Luminaires
(Light Fixtures) Version 1.0, (Effective date: Oct 1, 2011)
Within 1 second
Standby Power
Start Time
Criteria
© 2011 Fairchild Semiconductor
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Solutions for Today’s Low-Power LED Lighting Trends
Item
Reference
Standard Lamp
MR16, PAR16/20/30S/30L/38 dimension
Form
Operation
Frequency
Transient
Protection
Noise
Efficacy
ANSI C78.21-2003
Energy Star Program Requirements for Solid-State Lighting Luminaires,
Version 1.1, (Effective date: Feb 1, 2009)
≥ 120Hz
Energy Star Program Requirements Product Specifications for Luminaires
(Light Fixtures) Version 1.0, (Effective date: Oct 1, 2011)
≥ 120Hz (Dimming at All
Light Outputs)
Energy Star Program Requirements for Solid-State Lighting Luminaires,
Version 1.1 (Effective date: Feb 1, 2009)
IEEE C.62.41-1991 Class
A
Electromagnetic
Energy Star Program Requirements for Solid-State Lighting Luminaires,
and Radio
Version 1.1 (Effective date: Feb 1, 2009), LED Luminaries: Energy Star
Frequency
(Effective date: 01. Sep. 2011)
Interference
Operating Min.
Temperature
Criteria
FCC 47 CFR part 15
similar with CISPR15
Energy Star Program Requirements for Solid-State Lighting Luminaires,
Version 1.1 (Effective date: Feb 1, 2009)
Minimum of -20℃
NEMA SSL 1-2010
-40 to 60℃
Energy Star Program Requirements for Solid-State Lighting Luminaires,
Version 1.1 (Effective date: Feb 1, 2009)
Class A Sound Rating
Energy Star Program Requirements for Solid-State Lighting Luminaires,
Version 1.1 (Effective date: Feb 1, 2009)
From 24 to 45 lm/W
Category B: ≥70 lm/W
Effective Sep. 30, 2011
Energy Star Program Requirements Product Specifications for Luminaires
(Light Fixtures), Version 1.0 (Effective date: Oct 1, 2011)
≥65* lm/W Effective Sep. 1,
2013
Life Time
Residential Indoor: 25K
Energy Star Program Requirements for Solid-State Lighting Luminaires,
Hours
Version 1.1 (Effective date: Feb 1, 2009) & Energy Star Program
Residential Outdoor: 35K
Requirements Product Specifications for Luminaires (Light Fixtures) Version
Hours
1.0 (Effective date: Oct 1, 2011)
All Commercial: 35K hours
Warranty
Energy Star Program Requirements Product Specifications for Luminaires
(Light Fixtures), Version 1.0 (Effective date: Oct 1, 2011)
Safety
UL 8750, UL1598, UL153, UL1012 (Other than class2), UL1310 (class 2),
UL1574, UL2108, UL60950-1
© 2011 Fairchild Semiconductor
Non-Replaceable Drivers:
5 Years
Replaceable Drivers: 3
Years
4
Solutions for Today’s Low-Power LED Lighting Trends
II. LOW-POWER LED DRIVER DESIGN
CHALLENGES
Today’s LED driver designs face the following
challenges and these become the design constraints to
be balanced and prioritized:
 Development cycle-time

Cost

Design complexity

Finding a power topology that meets the input
and output voltage-current parameters,
thermal design, safety regulations, and
protection needs

Efficiency and efficacy

Meeting global regulations, i.e. reducing
power losses, power factor correction and
low THD in the LED driver

Reliability and lifetime of the driver

Constant current output tolerance

Dimming and dimming range (phase cut
dimmer requirement, dimming ratio, inrush
current limit, damping circuit, bleeder, etc.)

No flicker

Limited printed circuit board (PCB) space or
volume (height) constraints

Protections – OVP, OCP, OTP, short-circuit
LED, open-circuit LED

Operating temperature

Vendor selection and consolidation
MR11/16 Lamp LED System Configuration
The typical design of existing halogen designs is
shown in Figure 6.
Fig. 6.
Existed Conventional Halogen Infra structure
The input voltage can be DC 12V or 24V or plugged
directly into a 120V or 230V AC mains supply. The
12V or 24V can also be derived from a simple
transformer that takes the mains AC voltage and
outputs a 12 V / 24V AC input to the light socket. The
LED replacement needs to be controlled as a
constant-current source. A 4 W LED MR lamp is the
equivalent to a 20W halogen lamp design. Diming is a
feature found on some models, with the trend toward
dimming increasing in availability.
MR11/16 Lamp LED Driver Design Challenges
The top challenges for the MR11/16 design are the
lack of standards on the lamp fixture and the bulb
shape, the power factor, total harmonic distortion
requirement (Energy Star for LED luminaries ≥0.9,
integral lamp ≥0.7 for >5W), and low system power
efficiency. The small space for the LED driver can be
appreciated by considering the Fig. 7 lamp dimensions,
which must include the driver.
III. LOW-POWER LED APPLICATION
ANALYSIS
The following reviews low-power LED lighting; its
construction, function, design challenges, and trends
by application.
MR11/16 LED Lamp
The MR11/16 lamp is typically a halogen lamp and
common types are 20W, 35W, and 50W ratings.
© 2011 Fairchild Semiconductor
Fig. 7.
MR Lamp Dimensions
There are two types of printed circuit board form
factors. One shape, shown in Fig. 8, is round to adapt
with the LED module back side. The round diameter
should be smaller than 30 mm with taller components
located within 5 mm from the center connector.
5
Solutions for Today’s Low-Power LED Lighting Trends
Fig. 8.
MR Lamp Round Type PCB Design
The other, shown in Fig. 9, is vertical; it needs to be
smaller than 30 x 20 mm.
Fig. 9.
MR Lamp Vertical Type PCB Deign
MR11/16 Lamp Fairchild Solutions
If the input voltage is 12V or 24V DC, the LED
driver DC-DC topology choice is either a boost or buck
topology. If the LED total string forward voltage is
higher than the rectified input voltage, use a boost
topology; otherwise, use the buck topology. The
DC-DC power stage efficiency is high; it can generally
reach up to 90%. However, the ballast transformer
efficiency is poor. The ballast transformer is not a
switched-mode power supply (SMPS), just a
transformer converting 110V/220VAC to 12V/24VAC.
Although the DC-DC power stage efficiency is high,
the total system efficiency for the AC-DC transformer
+ DC-DC topology is low.
The poor system efficiency and PFC and THD
requirement need to be solved for the MR LED lamp
driver to fit within a limited small PCB space. The
current solution using an AC-DC transformer plus
© 2011 Fairchild Semiconductor
DC-DC topology is the current installed infrastructure:
a Halogen socket and ballast transformer. It results in
saving on installation investment cost, but electrical
efficiency is sacrificed. This infrastructure trend is to
be replaced by a more efficient configuration.
Manufacturers are starting to release an AC-DC MR
lamp into the market place.
The AC-DC MR lamp integrates the LED driver into
the lamp case without the need for the ballast
transformer. It is possible to achieve over 80% total
power efficiency in this configuration. In general, it is
not easy to build an AC-DC LED driver board into the
small bulb case while also meeting PF and THD
requirements in the application. It is also preferred not
to use an electrolytic capacitor whose life time is less
than the other semiconductor components or passive
electric components like the resistors, ceramic
capacitors, and inductors. The AC-DC MR-type LED
lamp design is a new design challenge.
Fairchild suggests a new LED driver device to solve
the AC-DC issues; the FL7701, shown in Fig. 10. It is a
“smart” non-isolated PFC buck LED driver solution.
With direct AC line input voltages, it is possible to
achieve a small PCB outline adaptable to the MR lamp
case. This LED driver device eliminates the need for
all electrolytic capacitors typically used for the input,
output, and IC VCC voltages. Eliminating the
electrolytic capacitors lengthens the product life and
reduces the PCB space, while resulting in a low BOM
cost. Using only a few external components, it meets
PF and THD requirements, while achieving efficiency
over 80%. The buck topology also has the advantage of
constant output current (reduced ripple current) versus
a boost design, since the inductor is placed in series
with the output, i.e. the buck topology looks like a
constant current source to the LED load. The boost
topology has discontinuous output current unless an
output capacitor is used to filter the ripple current. A
waveform comparison is shown in Fig. 11.
6
Solutions for Today’s Low-Power LED Lighting Trends
Vsup
D1
+ VLED -
ILINE
LED
Load
L
IL
FL7701
VCC
C
VSUP_SEN
DSG
ZCD_OUT
HV
HV
Device
DSG: Digital Sine-Wave Generator
HV Device : High-Voltage Device
DAC_OUT
Driver
S
Reference
OUT
Isw
Q
R
CS
GND
Fig. 10. Smart Non-Isolated PFC Buck LED Driver Solution
Fig. 11. Figure 11 Buck versus Boost Topology Comparison
IV. A19, E14/17, E26/27 BULB LAMP
Some bulb types are known as “Edison socket” and
“candle lights.” The majority are incandescent light
bulbs with CFL or LED replacements gaining the
majority of the application requirements.
A19, E14/17, E26/27 Socket Bulb Configuration
When input voltage is direct from the AC mains line,
the socket types are: E14/17 (candle), A19/E26/27
(screw type) with the power rating of 1~5W for candle
lights and 4~17W for the incandescent replacement.
The form factor is shown in Fig. 12 and Fig. 13.
Fig. 13. Example of Socket Bulb Type (L: 105mm, D55mm, B26mm)
A19, E14/17, E26/27 Socket Bulb LED Driver
Design Challenges
The LED driver design challenges for the candle
light is the small PCB space. It is smaller than the MR
lamp space and operates from AC input voltage lines.
The incandescent lamp replacement targeted for a LED
driver design has a larger PCB space than the candle
lamp or MR type lamp, but the power rating is larger,
so the LED driver is larger. The net effect is the PCB
space is limited, similar to the candle lamp. PF and
Fig. 12. Example of Candle Type (L: 99mm, D: 26mm, E: 17mm)
© 2011 Fairchild Semiconductor
7
Solutions for Today’s Low-Power LED Lighting Trends
THD are almost mandatory for the socket bulb designs
and there is the extra burden of dimmer operation.
The PCB form factor for the E26/27 bulb with
socket-side parabolic shape is socket side: 20 mm,
LED module side: 35 mm, width: 70mm (see Fig. 14).
A19, E14/17, E26/27 Socket Bulb Fairchild
Solutions
Isolation-type driver choices are preferred for safety.
In this power range, the preferred LED driver solution
is the flyback topology. With PF and THD becoming
mandatory for candle lights, although it is a low-power
application; many designers are using the single-stage
flyback solution. The single-stage PFC flyback
topology reduces PCB size because it can eliminate the
input electrolytic bulk capacitor. A further reduction in
component count is realized by using a single-stage
Primary-Side Regulation (PSR) flyback solution. With
its low BOM cost, isolated characteristic, PFC, and
wide input voltage range; the PFC PSR flyback is
poised to become the preferred LED driver topology.
TABLE 3. FAIRCHILD PSR CONTROLLERS
Solutions
Product
Number
Fig. 14. Example E26/E27 PCB Form Factor
Efficiency needs to be over 75%. Dimmer design
requirements include being compatible with various
holding currents, operating linearly over a wide range
of light amplitude, and preventing flicker.
PSR and PSR PFC
Flyback
Controller IC
FL103 (SOIC-8)
FL7730 (SOIC-8)
FL7732 (SOIC-8)
Controller IC with
integrated
MOSFET
FSEZ1317NY (DIP-7)
FSEZ1317MY
(SOIC-7)
In the PSR topology, no secondary-side feedback is
required; which eliminates the opto-isolator, the error
amplifier (such as TL431), and the compensating and
bias resistors and capacitors. Fig. 15 illustrates a
simplified PSR schematic.
Passive
Filter
VS
BD
FL103
FSEZ1317
Fig. 15. Primary Side Regulator Schematic
© 2011 Fairchild Semiconductor
8
Solutions for Today’s Low-Power LED Lighting Trends
The advantages of PSR flyback topology include:
 The single-stage solution limits the number of
components and ultimately fits into a smaller
design space.
 The FL103 50kHz operating switching
frequency helps the flyback magnetic
transformer fit within volume constraints.
 The integrated MOSFET option with the
FSEZ1317 reduces the component count,
saving additional PCB space.
 The reduction in components from a PSR
topology helps meet cost reduction pressure.
 No secondary-feedback circuits are needed,
which creates an immediate reduction in
components and an improvement in reliability
(without counting the opto-isolator or TL431).
 Fairchild’s PSR topology includes
TRUECURRENT™ technology, the industry
leading-edge constant-current performance of
<±3 %, which provides consistent high-quality
light radiation.
 The solution is isolated.
 The single-stage flyback topology can meet
PF and THD requirements.
The PSR flyback operates in two modes, Constant
Voltage (CV) and Constant Current (CC). LED drivers
should operate in the CC Mode to better control the
light output from the LED string. Fig. 16 shows the I-V
characteristics of the PSR regulated flyback.
Fig. 16. I-V Output Characteristics of a PSR Flyback LED Driver
Discontinuous Conduction Mode (DCM) is
preferred for PSR because it allows for better output
regulation. Typical waveforms are shown in Fig. 17.
© 2011 Fairchild Semiconductor
Fig. 17. Waveforms of DCM Flyback Converter
When operating in Constant Voltage regulation
mode, during the inductor current discharge time tDIS,
the sum of the output voltage and diode
forward-voltage drop is reflected to the auxiliary
winding side. Since the diode forward-voltage drop
decreases as current decreases, the auxiliary winding
voltage reflects the output voltage at the end of diode
conduction time tDIS. By sampling the auxiliary
winding voltage at the end of the diode conduction
time, the output voltage information is obtained.
When operating in Constant Current regulation
mode, the output current can be estimated using the
peak drain current IPEAK and the inductor current
discharge time tDIS because the output current is the
same as the average of the diode current in steady state.
With Fairchild’s TRUECURRENT™ technology,
constant current output can be precisely controlled.
For more LED driver design information using
primary-side regulated controllers, reference Fairchild
application notes AN-9735 — Design Guideline for
LED Lamp Control Using Primary-Side Regulated
Flyback Converter, FAN103 & FSEZ1317 and
AN-9741 — Design Guideline for LED Lamp Control
Using Primary-Side Regulated Flyback Converter,
FL103M. These are on the Fairchild website under
LED Lighting Low Power at the following address:
http://www.fairchildsemi.com/applications/diagrams/l
ighting_low_power.html
9
Solutions for Today’s Low-Power LED Lighting Trends
V. PAR16,20,30,38 LAMP
PAR16,20,30,38 Lamp System Configuration
These lamp types are AC voltage input, power rating
between 4W~20W, socket is screw type E26/27 or 2
pin type GU10, as shown in Fig. 18.
good solution is the single-stage flyback control PWM
IC with CRM PFC, space permitting. The advantage is
less design complexity with good efficiency.
Compared with a complex two-stage approach, it
provides high PF and low THD and does not require an
input electrolytic bulk capacitor. Fig. 20 shows a basic
single-stage PFC schematic.
No Input Bulk Capacitor
Passive
Filter
ZCD
Fig. 18. Example PAR Lamp Dimensions (L: 95mm, D: 92mm, B:
BD
26mm)
With the larger lamp size, there is more space to
contain the LED driver solution and PF and low THD
are mandatory.
PAR16,20,30,38 Lamp LED Driver Challenges
The higher wattage values of these LED lamps can
create a higher Vds,peak across the MOSFET, resulting in
the need for a higher BVDss-rated MOSFET. The
BVDss rating must derate for the high-voltage spike
due to a higher input current. Fig. 19 shows the voltage
spike as the sum of Vds,peak = VIN+nVO+VOS where nVO
is the reflected output voltage, also known as VRO.
CRM PFC PWM IC
PFC
FL6961
OR
FL7930B/C
CC&CV
isolated
feedback
Fig. 20. Representative Single-Stage PFC Schematic
Fairchild solutions are shown in Table 4 with a
comparison of single-stage flyback versus a two-stage
approach compared in Table 5.
TABLE 4. FAIRCHILD SINGLE-STAGE PFC
FLYBACK SOLUTIONS
Single Stage
PFC Flyback
Solutions
Product
Number
FL6961 (SOIC-8)
Controller IC FL7930B/FL7930C (SOIC-8)
TABLE 5. SINGLE-STAGE VS. TWO-STAGE LED DRIVER
Single Stage
Two Stage
VIN
Universal
Universal
Configuration
Flyback
Boost + Flyback
Switch
~800V
MOSFET~200V
Rectifier
~500V MOSFET
X 2ea
~ 100V Rectifier
Control IC
1ea PWM IC
2ea PWM IC
(or Combination
Controller)
Electrolytic
Capacitor
Output (~100V)
DC Link (450V)
Output (~100V)
Efficiency
Higher
Lower
Output Ripple
Current
Higher
Lower
BOM
Lower
Higher
Fig. 19. Vds,peak vs. MOSFET Derating
A snubber is used to limit the VOS peak voltage spike,
but the snubber dissipates energy, which decreases the
LED driver efficiency:
(1)
PAR16,20,30,38 Lamp Fairchild Solutions
The LED driver designer can chose among the PSR
PFC Flyback, a single-stage PFC flyback, or consider a
two-stage approach. The PSR PFC solution described
in the previous section is a good choice for this LED
driver topology. In certain designs, however, another
© 2011 Fairchild Semiconductor
10
Solutions for Today’s Low-Power LED Lighting Trends
In addition to the previously mentioned PSR LED
design driver application notes, reference AN-9737 —
Design Guideline for Single-Stage Flyback AC-DC
Converter Using FL6961 found on the Fairchild
website under LED Lighting Low Power at:
http://www.fairchildsemi.com/applications/diagrams/l
ighting_low_power.html
VI. CONCLUSION
Low-power LED driver applications were reviewed,
presenting trends and challenges. Although there are
differences in the various types of LED lamps, there
are only a few different requirements for the LED
driver by lamp type. In general, the basic requirements
are similar: a low BOM count and cost, small outline
for the PCB, high efficiency, high PF, and low THD.
Fairchild solutions include the AC-DC non-isolated
PFC buck topology or single-stage PFC primary-side
regulation offline topology, reducing the need for
multiple suppliers and technology inputs. Visit
Fairchild’s low-power LED website for information on
LED driver controllers, discrete semiconductors,
reference
designs,
and
application
notes:
http://www.fairchildsemi.com/applications/diagrams/l
ighting_low_power.html
In addition, Fairchild’s Global Power ResourceSM
Center is the industry standard for customer design
support. The site offers online tools, FAE contacts, and
information about regional centers staffed by power
engineers. Fairchild Semiconductor: Solutions for
Your Success™.
REFERENCES
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
U.S. Department of Energy: Solid State Lighting website,
http://www1.eere.energy.gov/buildings/ssl/index.html
Cree’s Lighting the LED Revolution, LED 101,
http://www.creeledrevolution.com/learn
U.S. Department of Energy , Solid-State Lighting: Brilliant Solutions
for America's Energy Future,
http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/ssl_broc
hure_june2011.pdf
Business Wire , 2010 Worldwide High-Brightness LED Market Grew
93 Percent According to Strategies Unlimited,
http://www.businesswire.com/news/home/20110223005343/en/2010Worldwide-High-Brightness-LED-Market-Grew-93
U.S. Department of Energy, SSL Research and Development
Multi-Year Program Plan Mar 2011 (Updated May 2011),
http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/ssl_myp
p2011_web.pdf
U.S. Department of Energy: Solid State Lighting website,
http://www1.eere.energy.gov/buildings/ssl/sslbasics_whyssl.html
U.S. Department of Energy, SSL Research and Development
Manufacturing Roadmap July 2011,
http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/ssl_man
uf-roadmap_july2011.pdf
Fred Welsh, Cost Trends for Solid State Lighting, DOE 2011
Solid-State Lighting Market Introduction Workshop,
http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/welsh_c
ost_sslmiw2011.pdf
Brian Johnson is the Lighting Specialist for
Fairchild’s LED lighting products segment in
Americas and Europe. He joined Fairchild after 20+
years of rotating in Development and Marketing
positions in the power electronics industry. He
graduated from Purdue University with a B.S.E.E.
and M.S.E.E.
James Lee is the Marketing Specialist for
VII.
CONTACT INFORMATION
To contact Fairchild Semiconductor, please go to:
http://www.fairchildsemi.com/cf/sales_contacts/.
For information on other products, design tools, and
sales contacts, visit: http://www.fairchildsemi.com
© 2011 Fairchild Semiconductor
Fairchild’s lighting products segment. He has
worked for over eight years as a power solution
semiconductor development marketer at Fairchild.
He graduated from Ajou University with a B.S.E.E.
and L.L.B Laws.
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