High Brightness LED Driver Solutions
for General Lighting
Created by Bernie Weir
World of Lighting
• ~ 20-22% of electrical energy is used for lighting of
which 40% is for incandescent lighting, this represents
2000 TWh/year
Residential
28%
Industrial 16%
Streetlighting
8%
Restaurants,
Retail and
Services 48%
>70% of the Energy Usage is
Outside of the Residential Market
Source: OSRAM
2
LED Technology Forecast and Impact
US DOE January 2009
3
LED Optical Characteristics
• Chromaticity
• Some defined “box” in the white area
on or near the Black Body Locus
• Bin sizes (x, y coordinates) varies by
supplier
• Brightness (luminus flux)
– All the “light” output into a
sphere
– Factors in human sensitivity to
light of different wavelengths
4
Challenges of Driving LEDs
All are
White LEDs
Nichia Rigel
NJSW036AT
– Forward voltage varies by color, current & temperature
– “Color point” shifts with current and temperature, more pronounced with Red and Amber
5
Operating Relationship
Electrical, Optical & Thermal
1
2
Luxeon Rebel
White
3) Higher
1) Increasing drive
power raises Tj,
current, increases flux
reduces flux (light out)
2) Higher
current,
increases Vf & power
6
OSRAM Platinum
Dragon
3
Seoul
Semiconductor
Z1
Thermal Path is Critical to LED Lifetime
5mm LED
Lighting-class LED
No Thermal
path
Thermal path
•
•
•
7
5mm lamps have almost no
thermal path
Rth >350 ºC/W typical
Chip (TJ) and phosphor can
essentially cook themselves
•
•
•
Lighting-class LEDs are designed for
high temp operation
Rth <10 ºC/W typical
Lamp can stay within data sheet
parameters with good thermal design
LED Lifetime
110%
Lumen Output (%)
100%
90%
100 W Incandescent
5mm LED
42W CFL
50 W Tungsten Halide
400 W Metal Halide
25 W T8 Fluorescent
Lighting-class LED
80%
70%
60%
50%
40%
0
10
20
30
40
50
60
Operating Time (k hrs)
•
70
80
90
100
Courtesy LRC, Rensselaer Polytechnic Institute
All conventional light sources dim over time, even LEDs
• Standard light sources fail (open filament etc)
• Properly designed LEDs dim gracefully
End of life is based on Lumen Maintenance (L70) which is a function of
operating temperature
•
8
Application Drives LED Selection
• What is the area/pattern to be lit?
– Linear strip or path
– Spot
– Area
• Optics considerations (narrow or wide beam)
– Diffuser
– Reflector
– Lens
Reflector
• Thermal density and heat removal
• Size and lit appearance
9
Lens
LED Packaging Trends
•
•
•
•
•
•
10
Smaller size
Multi-high power chips
Multi-small chips
Phosphor coatings methods
Higher wattage packages
Deposited silicone primary lens systems
Arrangement of LEDs
•
Driving single strings of LEDs is highly preferred as it
provides ideal current matching independent of forward
voltage variation, Vout “floats”
•
Users do configure LEDs in Parallel/Series combinations
– Requires “matched” LED forward voltages
– If an LED fails open, the other LEDs may be overdriven
– Cross connecting and multiple parallel techniques try to
mitigate the risk of a fault
Series
If a LED fails open,
only 1 LED will be
have 2x the drive
current
Parallel
Series-Parallel
11
Cross connect
Example of a Low Current Driver
Features
•Constant current as AC voltage increases
•No delay in turn on after LED threshold
voltage is reached
•Bright LEDs at low voltages
•LEDs protected from voltage surge
NSI45025
New family of simple 2 terminal
Constant Current Regulators (CCR)
• 20, 25, and 35 mA current
• SOT123 and SOT223 packages
• 45 V maximum operation
110 V RMS, TP1 - 156 V P-P
115 Vac
25 mA 100 Ω
30 LEDs
TP2 - LEDs 108 V, 52% On
Current probe 25 mA
12
LED Driver Basics
AC
Mains
Non-Isolated or
Isolated Power
Conversion
Driver
LED(s)
•
The main function of a driver is to limit the current regardless of input and output
conditions across a range of operating conditions
•
Ac-Dc power conversion and driver regulation can be merged together into a single driver
or separated into two stages
•
The arrangement of LEDs and the luminaire specifications dictate the fundamental driver
requirements
•
Isolated solutions means there is no physical electrical connection between the AC line
voltage and the LEDs
13
Driver Operation
Constant Voltage
Constant Voltage and Constant Current
Regions
•
Range of current and/or voltage regulation
is driver/design specific
•
Driver “constant” current behavior may not
have a textbook relationship
•
Some drivers are designed for constant
power so LED forward voltage determines
current
Constant Current
•
Output is voltage
Regulated or clamped
across a range of
current
14
•Output can be
designed to have tight
current limited
•The output voltage
depends on the LED
forward voltage
Basic Configurations
•
In a integral configuration, the power
conversion and constant current driver
are all within the light fixture
•
In a distributed configuration, the ac-dc
power conversion is separate from driver (s)
–
–
–
–
15
Tight coupling of LED light source to the
driver
Optimum efficiency
Simplifies installation
–
–
Modular applications like track and cove
lighting
Simplifies safety considerations
Increases flexibility
Offline LED Applications by Power Level
Based on Today’s LED Performance
•
Low Power
– 1-12 W
•
Medium Power
– 8-40 W
•
•
•
•
•
•
Under-cabinet lighting
Desk Lamps
Accent
Appliances
A lamp Bulb Replacement
•
•
•
•
•
•
•
Down Lighting
Spot Light (PAR38) Equivalent
Decorative Light Fixtures
Bollards
Ceiling Fans
Freezer and Refrigerator Lights
High Efficiency LED Supplies (ballasts) (24 V/ 48 V)
•
Area Lighting
–
–
–
High Power
– >40 W
•
16
Street Lights
Fluorescent Lights
HID Replacement
High Efficiency LED Supplies (ballasts) (24 V/ 48 V)
Factors to Consider
•
Output Power
– Range of LED forward voltage
– Current – target, maximum
– LED arrangement
•
•
–
–
–
–
–
Efficiency
Power Factor
Size
Cost
Fault handling (short circuit, open
circuit, overload, over temperature
– Standards – Safety (UL,CSA,VDE)
– Energy Star
– Reliability
Power Source
– 115 Vac, Universal (US/EU),
Industrial – 208/277 Vac or other
– Low Voltage Lighting (landscape,
track etc)
– Solar / Battery
•
Functional Requirements
– Dimming – PWM, 0 - 10 V, Triac,
Wireless, DALI, Proprietary, Other
– Analog, Digital, or multi-level
dimming
– Lighting Control – occupancy,
motion, timer
17
Additional Requirements
•
Other Considerations
–
–
–
–
–
Mechanical connections
Installation
Repair / Replacement
Lifecycle
Logistics
Isolated Topology by Power Range
re
c
In
g
n
i
as
p
e
w
o
r&
P
e
w
o
e
D
r
ity
s
n
LLC HB resonant topology
Flyback is the best choice for
Low power and LLC is best
choice for highest efficiency
flyback
18
Offline LED Specific Standards
•
ENERGYSTAR™ SSL Specification (Version 1.1 -2/2009)
– Luminaire based limits, product specific requirements including power factor
– No “off state” power requirement rules out standard wall plug adapters, exception are
devices with smart controls, standby < 0.5 W in those cases Electromagnetic & RFI
per FCC 47 CFR Part 15/18
•
IEC 61347-2-13 (5/2006) - Requirements for DC or AC supplied
electronic control gear for LED Modules include:
– Maximum SELV operating output voltage <= 25V rms (35.3 Vdc)
– “Proper” /Safe operation under various fault conditions:
• No LEDs testing and 2x the rated LEDs or modules
• Output short circuited
– No smoke emission or flammability under malfunction
•
ANSI C82.xxx LED Driver specification in development
•
Safety – UL, CSA etc - UL1310 (Class 2) / UL 60950 / UL1012
– See appendix for more information
19
Basic Offline Topology
Discrete or
Analog (NCP4300A)
implementation
Flyback Controller
or converter
depending on
power
20
20 W+ Universal NCP1351 Controllers
Simple
Secondary
Control
Discrete
Regulator
Variable
Frequency
PWM Controller
External
HV FET
•Example based on NCP1351 20 W Universal input (DN06040)
•Can support 350 mA to 1 A, design set for 700 mA, 33 Vdc
21
NCP1351 LED Demo Board Performance
Efficiency across Vf and Line (Iout = 700 mA nom)
90%
80%
70%
Efficiency (%)
60%
50%
40%
30%
115 Vac
230 Vac
20%
125 x 37 x 35 mm
10%
0%
0
5
10
15
LED Voltage (Vdc)
22
20
25
30
Range of Low Power LED Driver Demo Boards
Pout based on 90-265 Vac input range
25
Integrated
HV FET
Pout (W)
20
15
10
5
0
23
NCP1013LED
NCP1014LEDGT
NCP1028LED
NCP1351LED
Non-isolated Offline Buck Configuration
• Peak current controlled topology
operating in deep continuous conduction
• Why:
– Option to eliminate need for large electrolytic
output capacitor
– Simple control scheme with “good” current
regulation
– Can take advantage of the ON Semiconductor
DSS capability to power driver directly from
the line
• Circuit should be optimized for the
number of LEDs
24
Inverted Peak Current Control Buck
25
Regulate Peak – Control Valley
•
Continuous Conduction Mode
– Current is always flowing through the inductor
26
•
L = (VIN,MAX – VOUT) * (VOUT / VIN,MAX) * (1/fs) *(1/ (%Ripple * Iout))
•
Must respect minimum on-time (LEB + Tpd + MOSFET turn-off time)
Example: NCP1216 PCC Buck Circuit
115 Vac
Iout = 500 mA (nom)
• NCP1216 is directly powered from the ac mains simplifying startup and operation
• Efficiency is a function of output power (current, # LEDs), external component
selection (FET, inductor, rectifier) and switching frequency
• Dimmable through opto-coupler for safety isolation
• DN06050 Design Note available demonstrates performance including EMI filtering
27
Considerations for 230 Vac Applications
•
•
•
Driving small strings of LEDs at high voltages results in extremely narrow duty cycles
Switching controllers have leading edge blank circuit of 200-400 ns before current is sensed
Switching frequency must be reduced for proper operation and input voltage is kept to a
minimum with a half wave rectified input circuit
D1
AC1
Q1
STD1NK60
MRA4003T3G
C1
100nF
230Vac
C2
1uF
400Vdc
D2
MMSD4148T1
10k
1/2W
AC2
1R
1W
1
0.4
2.2uF
400Vdc
2
6
4
5
LED
0.35
LED Current (A)
1mH
C5
8
3
NCP1200
C3
0.3
1uF
16Vdc
R2
U1
C4
NCP1200 - 40kHz
205
215
225
235
Input Voltage (Vac)
245
255
265
10uF
25Vdc
18k
1/4W
R3
0.25
28
2R2
1/4W
L1
R4
R1
0.2
195
R5
2k
1/4W
D3
MURA160T3
Tapped Inductor Approach
Extends Duty Ratio, Increase Iout
29
Power Factor Requirements for
Offline LED Drivers
•
IEC (EU) requirements dictate THD performance for Lighting (over 25 W),
other international standards apply depending on the region
•
US DOE ENERGY STAR™ includes mandatory PFC for Solid State
Lighting regardless of the power level. This is a voluntary standard and
applies to a specific set of products such as down lights, under cabinet
lights and desk lamps for example
– >0.7 for residential applications
– >0.9 for commercial applications
•
While not absolutely mandated in the for lighting in all countries, it may be
required based on the application:
– Utilities drive major commercial uses to have high PF at the facility level
– Moreover when utilities owns/service the streetlight it is in their interest to have
good power factor, typically > 0.95+
30
Class C Limits
This class applies to lighting equipment exceeding 25 W
Harmonic Order n
2
3
5
7
9
11 < n <= 39
λ is the circuit power factor
Maximum Value expressed
as a percentage of the fundamental input current
2
30*λ
10
7
5
3
The standard equates to a THD<35% (PF around 0.94).
In practice, lighting equipment suppliers may target THD<20%.
31
Improving Power Factor for Flyback Circuits
•
Traditional Flyback converters have a PF of ~0.5-0.55
•
Improving this to > 0.7 for low power applications does not require new
topologies, just circuit optimization
1u
– Passive technique (Valley-Fill)
– ONSEMI “haversine” flyback optimization
– Critical Conduction Mode Flyback
VF := 0
D6
VF := 0
D4
D1
VF := 0
VF := 0
1
D7
C2
D5
VF := 0
D2
VF := 0
VF := 0
1k
R2
1u
C1
•
For high power applications like street lights, a dedicated PFC boost
stage is normally used
32
D3
NCP1014GTG Demo Board
J1-1
1
R1
4R7
Line
D1
C1
D3
D2
L1 2.7mH
MRA4007
+ TESTPOINT
D4
C3
R2
1.5nF
47K
E1
1
100nF
MRA4007
J1-2
MRA4007
MRA4007
C2
220nF
1
D7
MURS320T3
R6
1R8
R7
1R8
J2-1
1
Neutral
1
D5
J2-2
+
T1A
FL1
C9
1000uF
R8
10R
R9
10R
1
4
Reduce bulk
cap to improve
power factor
LED Anode
1
MURA160
Fly Leads
D6
T1B
3
FL2
C8
R10
C10
10K
10nF
J2-5
+
1
1000uF
MMBD914LT1
LED Cathode
T1C
2
J2-6
1
1
E2
Output
capacitance
Increased
Q1
BC857
100
D8
24V
1
VCC
DRAIN
FB
3.3K
GND
3
2
4
NCP1014
R4
R13
10K
200
R5
Q2
BC846
C6
47uF
U2
R14
R15
2
2.2uF
3
C5
1
4
2.2K
100nF
1K
U1
R3
C4
R12
Off board
Reduce cap to
increase dynamic
self supply
frequency for
improved EMI
- TESTPOINT
- TESTPOINT
R11
820
1K
D9
5.1V
C7 2.2nF
Optional dimming components
Slow loop response
to improve power factor
33
8mm Primary-Secondary
Boundary
Performance of “Haversine” Flyback
•DN06051 design note illustrates how to modifying the NCP1014 for higher PF >
0.8 using the “haversine” flyback optimization which easily meets US Residential
Energystar Requirements
34
Demo: NCP1014GTG Portable Desk Lamp
Desk Lamp
NCP1014 LED Driver
with PF Correction
35
35 W Halogen
4 LED Cree MC-E
Multichip Array
Magnetic Transformer
Light
Source
Pin (W)
@ 120 Vac
Illuminance
(Lux)*
Power
Factor
Halogen
(35 W bulb)
41.7 W
744
0.961
Quad LED
10.9 W
795
0.857
Summary of Results
* Illuminance measures at 0.5 m
Achieving High Power Factor and
Low Distortion
High voltage dc node
NCP1652
PFC
Controller
Secondary side control
is not draw for simplicity
36
Area Lighting Considerations
Dimming
Control
NCP1652
PWM
Power Supply
AC
PFC
Isolated
DC-DC
DC
Output
LED
Module
w/ CCR
PWM
LED
Lamp
w/CCR
PWM
Two Stage Modular Approach
AC-DC + Constant Current Stages
LED
Lamp
w/CCR
•
Light output varies significantly
–
–
37
Poll Height and Spacing
Type of Traffic Flow (residential, city center)
•
Significant range of power and light levels required for
area lighting
•
One basic design can be scaled up or down in light
output by adding LED light bars
•
With a modular approach light bars are field
upgradeable
NCP1652 48 V Fixed Output Schematic
Ideal for Fixed Voltage Area Lighting
F1
2.5A
C1
C2
0.47
"X"
0.47
"X"
MRA4007T
C3
0.1uF
400V
R7
R6
365K
365K
D5
R9
R10
R11
30.1K
332K
365K
R2
560K
0.5W
R3
36K
3W
D10
C4
22uF
400V
D11
R4
27K
100 MMSD
MURS120T
4148T C6
6
470uF
D7
1
35V
MURS
R5
160T
+
C11
4.7uF
25V
C12
470pF
2.2K
R16
C13
33nF
100K
1nF
6
0 ohm
7
8
10
1. Crossed schematic lines are not connected.
2. Heavy lines indicate power traces/planes.
3. Z2/D9 is for optional OVP (not used).
4. L1 is Coilcraft BU10-1012R2B or equivalent.
5. L2 is Coilcraft P3221-AL or equivalent.
6. L3 is Coilcraft RFB0807-3R3L or equivalent.
7. Q1 and Q2 will require small heatsinks.
38
C23 0.1
D8
11
100,
63V
MUR860
3.3K
1/4W
Z4 (24V)
MMSZ5252B
SFH615A-4
U2
R22
10K
9
MMSD
4148T
4
1
3
2
R27
1K
R28
R29
102K
C26
R21
R18
C15 C16 C17 C18
Z3
MMSZ
5248B
Notes:
100, 1/2W 1nF
R26
2.7K
3.3 ohm
11
R17
39K
C24
R23
R25
C14
10nF
+
R24 C19 C20 C21 C22
Q1 SPP11N80C3
12
MMSZ
5245B
L3
3.3uH
R31
0.1
13
D9
8
C8
16
15
14 NC
Z2
8.6K
C10
R14
R13
7.32K
680pF
C9
R15
680uF,
63V x 3
100
49.9K
R12
(6:1)
100nF 2
400V
C5
100uF
35v
NCP1652
U1
T1
C7
5
R8
2K
1/2W
1
2
3
4
5
D6
0.1 0.1
1nF
R19
76.8K
Z1
0.1uF
1M
0.5W
MRA4007T
R1
1.5KE440A
AC
In
D1 - D4
1N5406 x 4
L2
L1
24K
10
R20
0.10
ohm
0.5W
1uF
U3
TL431A
C25
0.1
C27
2.2nF "Y"
NCP1652 90 Watt LED Supply
48V, 2A Out, 90-265VAC Input
R30
5.6K
48V
2A
_
NCP1652 Efficiency Results
Configuration: 48 V / 2 A
94
92
Efficiency (%)
90
88
86
115 V ac
230 V ac
84
82
80
10%
20%
30%
40%
50%
60%
% of Full Load
39
70%
80%
90%
100%
Modifying Secondary Side for
CC/CV Operation
Efficiency
Vf = 45 Vdc
40
NCL30000 CRM Isolated Flyback
•
Low Power (5-20 W) also need high power factor
– LED Drivers/Ballasts
– Downlights / Spot Lights / Outdoor Lighting
•
Key Objectives
–
–
–
–
–
•
41
Directly drive LEDs with tight constant current output regulation
High Power Factor >0.9, IEC Class C Harmonic Content
Greater than 80% efficiency at low power levels 5-15 W Pout, 83% typical
Scale-able to handle a range of power LEDs and current levels
Can support existing dimming solutions (TRIAC and Trailing Edge)
Design approach to achieve high power factor in a single stage uses a
critical conduction mode (CrM) fixed on-time flyback topology
NCL30000 Basic Application Diagram
AC
Line
Input
Dout
EMI
FILTER
Cin
RSU
Ra
D1
Cv
Rb
Rx
8
VCC
RL
OUT2
R1
RZCD
7
+
IN2+ 5
IN2- 6
-
Rt
NCL30000
1
MFP
NCS1002
Vcc
8
Q1
OUT1
-
IN1- 2
C1
R2
2
COMP
DRV
7
3
CT
GND
6
1
+
IN1+ 3
Ccomp
GND
Cc
4
CS
ZCD
Ry
4
5
Ctim
COUT
Rc
RCS
42
RLED
Theory of Operation
•
Fixed on-time control
results in sinusoidal
input current in phase
•
Key Requirements
– Input capacitance
must be very low
– Control bandwidth
must be low (<20 Hz)
to maintain constant
on-time over a line
cycle
•
43
Secondary feedback
controls on-time based
on line and load
NCL30000 Demo Requirements
•
Intended to supply 350 mA and drive a wide range of LEDs (4-15) LED
driver applications. Component selections to support 700 mA or higher
output current
•
Reference design is targeting <20 W with this transformer, board can
also support larger transformer for higher power
•
Scalable solution for different power levels
– 115 Vac Version - 90-130 Vac
– 230 Vac Version 180-265 Vac
– 90 – 305 Vac – Extended universal included 277 Vac - no Triac control
•
For Triac Dimming, on time has to be adjusted for a specific number of
LEDs to achieve best dimming performance. Default is 12 LEDs
•
Robust Protection
– Open LED, Shorted Output, Overload
44
NCL30000 Demo Board
Dual transformer footprints for 15 W / 30 W Designs
45
Efficiency and Current Regulation versus Load
NCL30000 115 Vac Demo Board
370
86%
84%
Efficiency ->
350
82%
340
80%
330
78%
320
76%
310
74%
300
72%
0
10
20
30
LED Forward Voltage (Vdc)
46
40
50
60
Efficiency (%)
LED Current (mA)
360
Power Factor and Harmonic Distortion
Input Current THD (%)
13
0.99
12
0.98
11
0.97
10
0.96
9
0.95
8
0.94
7
0.93
THD
Power Factor
6
5
0.92
0.91
4
90
95
100
105
110
115
Input Voltage (Vac)
47
1
120
125
130
0.9
135
Power Factor (PF)
NCL30000 115 Vac Demo Board
14
Line Dimmable LED Drivers
•
Triac dimmers (leading edge, phase cut) are
intended for resistive loads and tend to behave
badly when connected to an electronic
transformer
•
Some manufacturers have “specialized”
dimmers –for electronic transformers such as
low voltage track lighting
•
Moreover for commercial applications there are
also transistor based dimmers that have falling
edge control (three wire connection)
•
Triac dimming is common in residential a nd
retail application
48
Matching LED Driver to Dimmer
•A typical switch mode power supply feedback system will attempt to
maintain constant output over a wide range of input voltage by increasing
duty cycle or in this case on time
•For line dimming, LED current should reduce proportionately to reduction
of the RMS input voltage
•The maximum on time is set to limit the power at the nominal LED string
power
•During dimming, the controller will not be able to increase on time, so
natural dimming of the LED occurs in a predictable manner
49
Efficiency and Current Regulation versus Load
NCL30000 115 Vac Demo Board
60
Constant
Power
Region
50
LED Voltage (Vdc)
40
LED Power
Dimming Point
Constant
Current
Region
30
20
10
Short Protection
Region
0
0
100
200
300
400
LED Current (mA)
50
500
600
700
800
NCL30000 350 mA Isolated Flyback
400
90%
350
80%
300
70%
250
60%
200
50%
150
40%
100
30%
50
20%
0
20
30
40
50
60
70
80
Input Voltage (Vac)
51
90
100
110
120
130
10%
140
Efficiency
LED Current (mA)
115 Vac / 12 LED / Triac Dimming Version
NCL30000 350 mA Isolated Flyback
115 Vac Line Dimming Control - 12 LEDs in Series
400
350
LED Current (mA)
300
250
200
Leviton Sureslide
Leviton Electronic
150
Cooper Aspire
Lutron Skylark
Leviton Illumittech
100
Lutron Digital Fade
Leviton Rotary
GE DI 61
50
Lutron Toggler
0
0
20
40
60
80
100
Conduction Angles (degrees)
52
120
140
160
180
Comments on Triac and Transistor Dimming
• As illustrated, dimming range is highly dependent on the
characteristics of the wall dimmer
• Triac dimmers were originally designed for incandescent
lamps and presented a much higher load (4-5x higher) than
a LED replacement down-light
• Unfortunately each manufacturer has different dimmer
characteristics
• As LED lighting enters the mainstream we would expect
dimmer manufacturers to start optimizing their products to
LEDs
53
Power Factor and Harmonic Distortion
1.00
13
0.99
12
0.98
11
0.97
10
0.96
9
0.95
0.94
8
THD
Power Factor
7
0.93
6
90
115
140
165
190
215
Input Voltage (Vac)
54
240
265
290
0.92
315
Power Factor
Input Current THD
NCL30000 90-305 Vac Demo Board
14
Efficiency and Current Regulation versus Load
NCL30000 90-305 Vac Demo Board (Vout = 12 LEDs, 37 Vdc)
400
86%
84%
Efficiency ->
375
82%
350
78%
76%
74%
325
72%
300
90
110
130
150
170
190
210
Input Line Voltage (V ac)
55
230
250
270
290
70%
310
Efficiency (%)
Iout (mA)
80%
EMI Performance
NCL30000 Demo Board (90-305 Vac Version)
56
Isolated High PF Efficiency/Solutions
CRM + Resonant Half Bridge
Efficiency
90%
CCM single stage
NCP1652/NCL30001* (PWM dimmable)
85%
NCL30000
CRM
Flyback
Output Current
0.3-3 A
Universal Input
80%
25
57
50
75
Output Power
100
* Available Dec 2009
100-200 W CRM/LLC High Power
Streetlight Supply
NCP1397
58
50k hours of LED life is great but ….
Occasionally there can be failures
Caused by. . .
Some Application Are. . .
9LED infant mortality
9 Mission Critical
9Assembly Partial Defects
9 Safety Dependent
9Transients
9 Difficult Access
59
NUD4700 LED Shunt Protection
Current
Source
•Protects operation in the event of an open LED fault
•Supports up to 1 A with proper heat sinking
NUD4700 in
PowerMite Package
60
LED Lighting Must be Approached as a System
61
Conclusion
• Offline LED power solutions continue to evolve in a rapid
manner as new LEDs are introduced
• Variety of offline solutions depending on power level,
features, and performance
• ON Semiconductor has a complete portfolio of PFC and
PWM controllers and converters to address range of LED
power applications
• Visit the ON Semiconductor website to see what new
reference designs are being introduced optimized for
specific AC line powered LED applications
62
For More Information
•
View the extensive portfolio of power management products from ON
Semiconductor at www.onsemi.com
•
View reference designs, design notes, and other material supporting
the design of highly efficient power supplies at
www.onsemi.com/powersupplies
63