Non-Dimmable Lower Power LED Solutions

1
Non-Dimmable
Lower Power LED Solutions

2 • Steve West • Nov-12 Confidential Proprietary2
Low Power LED Driver Space
Decorative
and Globe
General Service
A19/A21
E26/7 Base
Small Constant
Current Drivers
Typically < 15 W
Directional/Spot
Lamps
GU10/PAR/BAR
Wide variety of power levels, form factors, many need isolation
Small Fixtures
Desk Lamps
Under-cabinet
Accent
E14
B22

Isolated Considerations
• For bulbs, protection from electrical shock protection can be
done by electrical or mechanical means
• Electrical isolation simplifies the mechanical design and
eases safety agency approval and allows the use of off the
shelf heat sinks and housings
• Transformer provides isolation
• Safe Extra Low Voltage Level is < 60 Vdc (UL1993, EN 60598-1 etc)
• < 18 LEDs in series (Vf ~ 3.3V) is the practical upper limit
• Opto-coupler feedback or primary side control (PSC)
compensates for any variation to line or load

Primary Side Control Block Diagram
CCCV
Control
Flyback
Controller
Advantages
• Reduces Parts Count
• Simplifies PCB Layout
• Saves Space
• Increases Efficiency
• Simplifies Safety Analysis
CCCV Loop Components
• Dual Op Amp
• TL431 or Zener Reference
• Bias for Opto-coupler
• Bias Regulator for Op Amp
• Current Sense Resistor
• Voltage Sense for OVP

Challenges of Primary Side Control
• Control algorithm must deal with many variables
• LED string voltage and input line voltage variation
• Component variation (transformers, FET, IC, resistors)
• Target is to precisely regulate current over Wide Vf support
• LED forward voltage changes with temperature and lot-to-lot
• No need to bin LEDs to get tight Vf
• One driver design can be used for a range of products (optics/LED etc)
simplifying design and reducing engineering cost
• Future proof designs so as LEDs improve, same driver can be used
• NCL3008x PSC family was designed to achieve best-in-class
performance using Quasi-Resonant Approach

Flyback Output Current
• t1 is the reset time of the
leakage inductor.
• tdemag is the primary inductor
reset time.
• IL,pk is the controlled magnitude
in a current mode circuit:
IL,pk = VCS / Rsense
• The controller measures t1, tdemag and control IL,pk to maintain Iout constant:
time
t1 t2
tdemag
ton
IL,pk
NspID,pk
Ipri(t)
Isec(t)
1
2sw
ref
out sec demag sw L , pkT
sp sense
V
I I ( t ) f t ,t ,T ,I
N R

NCL30080 Block Diagram
• Quasi-Resonant
Control for High
Efficiency and low
EMI
• PSR control
• Robust Protection
• Short Circuit
• Overvoltage
• Shorted Winding
• Vcc UVLO
• Shorted CS pin

NCL30080 Primary Side Controller
Line voltage
sensing
Line feed-forward adjustment
Inductor current
sensing
Leakage
inductance
reset time
sensing

NCL30080 is one of a Family
Name Pins Thermal
Foldback
Analog/Digital
Dimming
Adjustable
OVP
Application 5 Step LOG
Dimming
NCL30080A/B 6 No No No Retrofit/Ballast No
NCL30081A/B 6 No No No Dimmable Bulb Yes
NCL30082A/B 8 Yes Yes Yes Bulb/Ballast/
Smart Lighting/
Higher Power
No
NCL30083A/B 8 Yes Soft-start Yes Dimmable/ Higher
Power
Yes
• A: Latched faults (Output SCP, OTP, Winding/output diode SCP)
• B: All faults auto-recoverable
• Packages:
SOIC8 Available
In Q3

Review of NCL3008x Features
• Wide Vcc and low startup current simplify
biasing and achieving fast startup
• Wide Vcc range allows one design to
support range of LEDs without the need of
a regulator on Aux winding
• Strong drive capability with gate drive clamp
• Wide temperature range along with built in
auto-recoverable thermal shutdown
• Hysteretic OVP plus programmable over
voltage protection on 8 pin version
• Robust protection and dimming options
Typical Parmeters Value Units
Vcc(on) 18 Vdc
Vcc(off) 8.8 Vdc
Startup Current 13 µA
Vcc-OVP 28 Vdc
Maximum Vcc 35 Vdc
Gate Drive Clamp Voltage 12 Vdc
Sink Current 500 mA
Source Current 300 mA
Minimum Operating Temperature -40 °C
Maximum Operating Temperature 125 °C
IC Thermal Shutdown (TSD) 150 °C
TSD Hysteresis 50 °C

Vcc-min (Max) = 9.4 V
OVP (Min) = 26 V
AuxWindingBiasing
setsalimitforICoperation
LED Current (mA)
LEDForwardVoltage
480 700
22 V
9.5 V
7.6 V
14 V
Single transformer
can cover wide LED current
& Vf range with minor
BOM change (current setting
resistor)
Wide Vf Flexibility Means Designer Can use
One Transformer Design for Many Models

Typical NCL3008x
Current Regulation Variation
• Iout = 480 mA (nom)
• 3 LED = 9.5 V
• 7 LED = 21.9 V
• Same Transformer
and MOSFET
• Min-max Iout variation
was 12 mA
• Min:
– Vin =240 Vac
– Vf = 21.9 Vdc
– Iout = 476 mA
• Max:
– Vin =120 Vac
– Vf = 9.52 Vdc
– Iout = 488 mALine Voltage (Vac)

NCL30082 Efficiency from 4.6 – 10 W Pout
• Iout = 480 mA (nom)
• 3 LED = 9.5 V
• 7 LED = 21.9 V
• Same Transformer
and MOSFET
• Min-max Iout variation
was 12 mA
• Min:
– Vin =240 Vac
– Vf = 21.9 Vdc
– Iout = 476 mA
• Max:
– Vin =120 Vac
– Vf = 9.52 Vdc
– Iout = 488 mA

Flyback Controllers Support Buck-Boost
LED String
NCL30000
Controller
EMI
Filter
Mains
Input
+
Input Sense
LED Sense
Terminator
Current
Sensor
Scaling
Classic Flyback
Controller
With a classic Flyback controller, still need level shifter to sense LED current

NCL3008x Control Supports Buck-Boost
LED String
NCL30000
Controller
EMI
Filter
Mains
Input
+
Input Sense
LED Sense
Terminator
Current
Sensor
Scaling
NCL3008x
Series
Non-isolated buck boost with PSC also eliminates components like snubber
and improves efficiency

Reference Design Boards
• NCL30081LEDGEVB (Small Board)
• NCL30080/1 Isolated Flyback
• Intended for GU10 form factor
• 3-4 LEDs at 500 mA
• 100-265 Vac, 83% typ efficiency
• NCL30083FLYGEVB – 10W
• NCL30082/3 Isolated Flyback
• Intended for A19/PAR/Drivers
• 3-7 LEDs at 500 mA (9.5-22V)
• Resistor change for 700 mA (7-14V)
• 100-265 Vac, >87% typ efficiency
• NCL30083BB1GEVB – 12 W
• NCL30082/3 Non-isolated Buck-boost
• Intended for A19/PAR/Drivers
• 10-20 LEDs at 200 mA (30-60V)
• 100-265 Vac, >90% typ efficiency
34.1 X 17.3 X 16mm
Fits in a 22 x 60 mm cylinder
Schematic Change, Different Magnetics
6 fewer components

NCL30082/3 EVB - Typical Results
190
191
192
193
194
195
196
197
198
199
200
100 120 140 160 180 200 220 240 260
OutputCurrentinmA
Line Voltage
29Vout
60Vout
690
691
692
693
694
695
696
697
698
699
700
100 120 140 160 180 200 220 240 260
OutputCurrentinmA
Line Voltage
7.6Vout
14Vout
Flyback Schematic, 700 mA setting
Buck-Boost Schematic
78.0%
80.0%
82.0%
84.0%
86.0%
88.0%
90.0%
92.0%
94.0%
100 120 140 160 180 200 220 240 260
Efficiency
Line Voltage
Buck Boost
Flyback
Efficiency
Current Regulation
0.75
0.76
0.77
0.78
0.79
0.8
0.81
0.82
0.83
0.84
0.85
100 120 140 160 180 200 220 240 260
PowerFactor
Line Voltage
Buck Boost
Flyback
Power Factor

Trends in LEDs
• General trend is to move from high current (350-500 mA) to low to
medium current (60-150 mA) LEDs for omni-directional light sources
• Many LED manufacturers are developing High Voltage LEDs
• Everlight HV 95-111 V @ 20 mA)
• Philips Luxeon H (52 V@40 mA/98 V@40 mA/196 V@20 mA)
• CREE XT-E HVW (up to 48 V@ 22 mA) and XM-L HV
• Samsung LH934 Series
• Seoul Acriche MJT4040 (64 V@ 20 mA) and A5 Series
 Since high LED string voltages > 60 V (SELV) level, non-isolated
topologies are best suited

Non-Isolated Buck
• LEDs string does not need to be matched to line
voltage
• Efficiency can be >85% even at low power (< 4W)
• Does require some design work to optimize
• Low LED current ripple
• Higher parts count and EMI generated so filtering
is necessary
Driving Long Strings of LEDs
Linear
• Very simple to design, no EMI generated
• LED string voltage must be matched to input line
voltage
• Efficiency and current varies with line & LED Vf
• More LEDs are needed for same light output
since LEDs are off for 50% of period
• Large 100/120 Hz Ripple
AC Input
240 Vac

Power Factor and Ripple
• Linear & buck can achieve high power with some limitations
• 100/120 Hz current output
• Inefficient LED capacity utilization, (LEDs are off part of each cycle)
• Simplest linear solutions (bridge + resistor) only limits current
• If string voltage is higher than max Vin, boost topology can
be used which can achieve high PF and high LED utilization

Constant Current Regulators (CCR) Protect
LEDs from Being Overdriven
• CCRs are optimized linear drivers
• 2 terminal fixed current
• 10,25,30,40,50,70,350 mA
• 3 terminal adjustable current
• 60-100,90-160 mA
• Wide packages range from
SOD123 to DPAK
• 45 &120V maximum CCR
voltages
• 3 120V versions
Product Description
NSIC2020B 120 V, 20 mA Constant Current Regulator & LED Driver

Example: Bridge & 120V CCR
• LED string Vf length
• Efficiency
• Lumen Output
• Conduction time is the time the
LEDs are ON
~VIN
+
-
VAK
ICCR
+
-
IF(Total)
VF(Total)
VVV
VVV
PTotalF
MaxAKPTotalF
3)(
)()(
LED Range Conduction Time
P
TotalF
V
V
Ton
)(1
sin2
1%
VRMS +/- % VP+ VP- VF(Total)+ VF(Total)- %Ton (Min) % Ton (Max)
120 5 178.2 161.2 158.2 58.2 7.77% 78.82%
113.5 12 179.8 141.2 138.2 59.8 8.30% 78.42%
220 15 357.8 264.4 261.4 237.8 6.07% 53.72%
240 15 390.4 288.5 285.5 270.3 5.81% 51.30%
230 +6 / -10 344.8 292.7 289.7 224.8 5.77% 54.79%

CCR + Bridge on Low Mains
• 0.91 PF @ 127 VRMS
• 43.5 % THD
• 82% Efficiency @ 127 V
Both designs meet IEC61000-3-2-Class C EN 55022-Class B
Conducted < 2% EMI
~VIN
NSI45030AT1G
135V @
30mA
4 x MRA4003T3
• 0.97 PF @ 100 - 127 VRMS
• 21.1 % THD
• 44 % Efficiency @ 127 V
~VIN
NSIC2050
~ 60V @
50mA
4 x MRA4003T3

Capacitive Drop Addresses Ripple Issue
• The voltage across the
capacitor begins to rise
as the current flows
through the CCR +
LEDs
• Simply size the R1 and
C value
• Limits the voltage over
the CCR to 2 or 3 V.
• VERY small form factor
• Very high efficiency
4 x MRA4003T3P
Pg
VfR
VRI
C
1
1Re
2
*
R1 = 470kΩ
R2 = 120Ω
Vz = VLED + 4V
More examples and explanation
available on www.onsemi.com
application note: AND8492-D

Universal Input Voltage Buck Chopper
MRA4003
NSI45020AT1G
22 LEDs
~81 V
22 uF
NDD03N50Z
MMSZ15T1G
MPS4444
32 kΩ
330 kΩ
390 kΩ
MMSZ5260BT1G
2
211
)7.0(
R
RRVV
V z
o
R1
R2
VZ1
100 – 264 V

NCL30002 Buck Controller
• Hybrid Constant On Time/Peak Current CrM Control
• Accurate 485 mV Peak current limit (+/- 3.1% across – 40 to 125 ºC)
• ZCD detection to restart switching at zero inductor current
• Low 24 µA typical startup current allows fast startup time
• Integrated error amplifier architecture allows simple line feed-forward
implementation to control on-time for power factor correction

Low Ripple
Peak Current/Zero
Inductor Current
Restart
Typical PF ~ 0.6
Efficiency > 85% @ 4W
Off-the-shelf inductor
High Power Factor
Constant On Time/
Peak Current Limit
Typical PF > 0.9 and
Efficiency > 90% @ 15W
Based on LED Vf
Two Options for Buck Topology
Input Line Current

NCL30002 Low Ripple Buck
• Charge pump used to provide IC bias after startup
• Off the shelf, low cost standard inductors
• Low 24 piece bill-of-material count
Input Voltage 200-260 Vac 50/60 Hz
LED Forward
Voltage
150 Vdc
Output Current 25 mA dc
Harmonics EN61000-3-2 Class C
Efficiency >85% @ nominal line
Example Design

Current Regulation (150 V LED)

Efficiency at Vf=150 V, 25 mA (nom)

90-135 Vac (120 mA/up to 60 V Vf )
SOT23/SC59
BSS131 FET
7.7 Ω Rdson/240V Vgs
Design Highlights
• ~90% Efficient
•23 Component bill-of-
materials
• Off-the-shelf magnetics
•Example shows Optimization for Japan Market Bulbs

Performance Highlights
125 ms Startup Time

HiPF Buck Application Schematic

Design Guide Worksheet Tool

Example of NCL30002 Driver Design
NCL30002 Demo Board

Non-Dimmable <10 W HiPF Boost
NCP1075 Switcher and +/- 2% accurate NCP4328A CCCV Controller
• Off-the-shelf inductor, >91% efficient driving Vf string of 220V @ 30 mA (6.6 W)
• Typical PF > 0.96 and THD of <20% at 120 Vac
• < 20 msec typical startup time
• Perfect for High Voltage LEDs like CREE 48Vx5 XT-E or Philips Luxeon 200 V
Open LED
Protection
Current
Sense
PF
Optimizer
Actual Size:
24.1 x 34.7 mm

NCP1075 Boost Efficiency/Regulation
Vout = 213 V (nom)

NCP1075 Power Factor/Harmonic Content
Vout = 213 V (nom)

The NCP4328 consists of two OTA amplifiers providing constant current and constant voltage (CCCV) regulation for
switch mode power supplies. It features high accuracy voltage and current references and very low Icc consumption.
• <100 µA supply current
• ±0.5% Reference Voltage
Accuracy @ 25 ºC
• 62.5 mV +/- 2% Current
sense reference @ 25 ºC
• Improved efficiency
• Tight output voltage and
current regulation
• Up to 36 V operating range
• Wide temperature range – 40 to 125 ºC
• Available with integrated PWM modulated driver for
indication LED for adapters(B version)
• LED Lighting
• Notebook Adapters
• Battery Chargers
• Open Frame Power Supplies
NCP4328 Secondary Side CCCV Controller
• NCP4328A (LED Driver) TSOP-5
• NCP4328B (Adapter) TSOP-6
Others Features
Market & Applications
Ordering & Package Information
Overview
Key Features Block Diagram

Summary
• ON Semiconductor has solutions for all low power offline
driver topologies
• Flyback
• Buck-Boost
• Buck
• Boost
• Linear
• Primary Side Control approach optimized for tight accuracy
and wide Vf support for high production yield and reduced
development time
• General shift in market to address non-isolated topologies

Appendix

Measuring the Leakage Inductor Reset Time
• t1 is measured by monitoring the current in the clamping network.
.
.
Vbulk
Cclamp
Rclamp
Rsense
RCS
CCS
CS
Vout
, ,L pk sp leak p L pk
Lleak sp clamp O
I N k L I
t
S N V V
1 O out f
V V V
,
, , , , ,L pk clamp O p sp leak
t f I V V L N k1
kleak: leakage inductor
coefficient expressed as a part
of Lp.

Transformer Design
• Balance between performance and cost of the solution.
• Better regulation of the output current if duty-cycle > 50%
• The duty-cycle varies with the output voltage (number of LEDs and input
voltage (narrow mains design / universal mains design), thus as a
starting point, we can calculate the turn-ratio at the maximum LEDs
voltage Vout,max and Vin,min:
.
out f
sp in out f
V V
N V V V
0 5
,
,
,
.
out max f
out max f
sp
in min
V V
V V
N
V
0 5

Primary Peak Current and Inductance
• Select the switching frequency Fsw,min at minimum input voltage
(including the bulk capacitor ripple) and maximum output load Pout,max.
• Calculate IL,pk and Lp with:
, ,,
,
( )
21
2
2
sp out max lump sw minout max
L pk
out OVP fin,min ripple
N P C FP
I
V VV V
,
2
, ,
2 out max
p
L pk sw min
P
L
I F
, ( )out max out OVP out
P V I

Excel® Based Design Tool
NCL3008X Design Guide
Version 4.0
12/5/2012
Input Parameters Calculated Parameters Designer Input Calculated Results
This Design Guide is intended to aid the designer and is not intended as a guarantee of performance.
Line Input Calculated Parameters
Maximum Line Voltage 265 V ac Primary Inductance 709 µH
Minimum Line Voltage 100 V ac Peak Primary Current 0.747 A
Line Frequency 50 Hz Secondary Current 0.846 A RMS
Primary Current 0.326 A RMS
Load
LED Vf Min 9 V dc
LED Vf Max 22 V dc Minimum Frequency 55 kHz
LED Current 480 mA dc Maximum Duty Cycle 57%
LED Dynamic Resistance 4 Ω Minimum Duty Cycle 7% See Notes
Ripple Current 50 mA P-P
Peak FET Voltage1 441 Volts
Architecture FET Current 0.326 A RMS
Topology Flyback
Turns Ratio 3 Pri:Sec Peak Output Rectifier Voltage1 147 Volts
Front End Valley Fill
Maximum SwitchingFrequency 120 See Notes Vcc Rectifer Voltage1 180 Volts
Min Vcc Voltage 11 See Notes
Max Vcc Voltage 26.88888889 See Notes Output Capacitance 21.77 µF
RMS Capacitor Current 0.646 A RMS
Rsense 0.78 Ω
µF
Valley Fill Storage Capacitors 21.12 µF

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