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
...
3 • Steve West • Nov-12 Confidential Proprietary3
Isolated Considerations
• For bulbs, protection from electrical shock pr...
4 • Steve West • Nov-12 Confidential Proprietary4
Primary Side Control Block Diagram
CCCV
Control
Flyback
Controller
Advan...
5 • Steve West • Nov-12 Confidential Proprietary5
Challenges of Primary Side Control
• Control algorithm must deal with ma...
6 • Steve West • Nov-12 Confidential Proprietary6
Flyback Output Current
• t1 is the reset time of the
leakage inductor.
•...
7 • Steve West • Nov-12 Confidential Proprietary7
NCL30080 Block Diagram
• Quasi-Resonant
Control for High
Efficiency and ...
8 • Steve West • Nov-12 Confidential Proprietary8
NCL30080 Primary Side Controller
Line voltage
sensing
Line feed-forward ...
9 • Steve West • Nov-12 Confidential Proprietary9
NCL30080 is one of a Family
Name Pins Thermal
Foldback
Analog/Digital
Di...
10 • Steve West • Nov-12 Confidential Proprietary10
Review of NCL3008x Features
• Wide Vcc and low startup current simplif...
11 • Steve West • Nov-12 Confidential Proprietary11
Vcc-min (Max) = 9.4 V
OVP (Min) = 26 V
AuxWindingBiasing
setsalimitfor...
12 • Steve West • Nov-12 Confidential Proprietary12
Typical NCL3008x
Current Regulation Variation
• Iout = 480 mA (nom)
• ...
13 • Steve West • Nov-12 Confidential Proprietary13
NCL30082 Efficiency from 4.6 – 10 W Pout
• Iout = 480 mA (nom)
• 3 LED...
14 • Steve West • Nov-12 Confidential Proprietary14
Flyback Controllers Support Buck-Boost
LED String
NCL30000
Controller
...
15 • Steve West • Nov-12 Confidential Proprietary15
NCL3008x Control Supports Buck-Boost
LED String
NCL30000
Controller
EM...
16 • Steve West • Nov-12 Confidential Proprietary16
Reference Design Boards
• NCL30081LEDGEVB (Small Board)
• NCL30080/1 I...
17 • Steve West • Nov-12 Confidential Proprietary17
NCL30082/3 EVB - Typical Results
190
191
192
193
194
195
196
197
198
1...
18 • Steve West • Nov-12 Confidential Proprietary18
Trends in LEDs
• General trend is to move from high current (350-500 m...
19 • Steve West • Nov-12 Confidential Proprietary19
Non-Isolated Buck
• LEDs string does not need to be matched to line
vo...
20 • Steve West • Nov-12 Confidential Proprietary20
Power Factor and Ripple
• Linear & buck can achieve high power with so...
21 • Steve West • Nov-12 Confidential Proprietary21
Constant Current Regulators (CCR) Protect
LEDs from Being Overdriven
•...
22 • Steve West • Nov-12 Confidential Proprietary22
Example: Bridge & 120V CCR
• LED string Vf length
• Efficiency
• Lumen...
23 • Steve West • Nov-12 Confidential Proprietary23
CCR + Bridge on Low Mains
• 0.91 PF @ 127 VRMS
• 43.5 % THD
• 82% Effi...
24 • Steve West • Nov-12 Confidential Proprietary24
Capacitive Drop Addresses Ripple Issue
• The voltage across the
capaci...
25 • Steve West • Nov-12 Confidential Proprietary25
Universal Input Voltage Buck Chopper
MRA4003
NSI45020AT1G
22 LEDs
~81 ...
26 • Steve West • Nov-12 Confidential Proprietary26
NCL30002 Buck Controller
• Hybrid Constant On Time/Peak Current CrM Co...
27 • Steve West • Nov-12 Confidential Proprietary27
Low Ripple
Peak Current/Zero
Inductor Current
Restart
Typical PF ~ 0.6...
28 • Steve West • Nov-12 Confidential Proprietary28
NCL30002 Low Ripple Buck
• Charge pump used to provide IC bias after s...
29 • Steve West • Nov-12 Confidential Proprietary29
Current Regulation (150 V LED)
30 • Steve West • Nov-12 Confidential Proprietary30
Efficiency at Vf=150 V, 25 mA (nom)
31 • Steve West • Nov-12 Confidential Proprietary31
90-135 Vac (120 mA/up to 60 V Vf )
SOT23/SC59
BSS131 FET
7.7 Ω Rdson/2...
32 • Steve West • Nov-12 Confidential Proprietary32
Performance Highlights
125 ms Startup Time
33 • Steve West • Nov-12 Confidential Proprietary33
HiPF Buck Application Schematic
34 • Steve West • Nov-12 Confidential Proprietary34
Design Guide Worksheet Tool
35 • Steve West • Nov-12 Confidential Proprietary35
Example of NCL30002 Driver Design
NCL30002 Demo Board
36 • Steve West • Nov-12 Confidential Proprietary36
Non-Dimmable <10 W HiPF Boost
NCP1075 Switcher and +/- 2% accurate NCP...
37 • Steve West • Nov-12 Confidential Proprietary37
NCP1075 Boost Efficiency/Regulation
Vout = 213 V (nom)
38 • Steve West • Nov-12 Confidential Proprietary38
NCP1075 Power Factor/Harmonic Content
Vout = 213 V (nom)
39 • Steve West • Nov-12 Confidential Proprietary39
The NCP4328 consists of two OTA amplifiers providing constant current ...
40 • Steve West • Nov-12 Confidential Proprietary40
Summary
• ON Semiconductor has solutions for all low power offline
dri...
41 • Steve West • Nov-12 Confidential Proprietary41
Appendix
42 • Steve West • Nov-12 Confidential Proprietary42
Measuring the Leakage Inductor Reset Time
• t1 is measured by monitori...
43 • Steve West • Nov-12 Confidential Proprietary43
Transformer Design
• Balance between performance and cost of the solut...
44 • Steve West • Nov-12 Confidential Proprietary44
Primary Peak Current and Inductance
• Select the switching frequency F...
45 • Steve West • Nov-12 Confidential Proprietary45
Excel® Based Design Tool
NCL3008X Design Guide
Version 4.0
12/5/2012
I...
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Non-Dimmable Lower Power LED Solutions

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Summary
1. ON Semiconductor has solutions for all low power offline driver topologies: Flyback, Buck-Boost, Buck-Boost, Linear

2. Primary Side Control approach optimized for tight accuracy and wide Vf support for high production yield and reduced development time

3. General shift in market to address non-isolated topologies

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  • Typical CCCV circuit, may also need a discrete reference which consist of a Bipolar transistor/zener and cap
  • Non-Dimmable Lower Power LED Solutions

    1. 1. 1 Non-Dimmable Lower Power LED Solutions
    2. 2. 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
    3. 3. 3 • Steve West • Nov-12 Confidential Proprietary3 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
    4. 4. 4 • Steve West • Nov-12 Confidential Proprietary4 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
    5. 5. 5 • Steve West • Nov-12 Confidential Proprietary5 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
    6. 6. 6 • Steve West • Nov-12 Confidential Proprietary6 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
    7. 7. 7 • Steve West • Nov-12 Confidential Proprietary7 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
    8. 8. 8 • Steve West • Nov-12 Confidential Proprietary8 NCL30080 Primary Side Controller Line voltage sensing Line feed-forward adjustment Inductor current sensing Leakage inductance reset time sensing
    9. 9. 9 • Steve West • Nov-12 Confidential Proprietary9 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
    10. 10. 10 • Steve West • Nov-12 Confidential Proprietary10 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
    11. 11. 11 • Steve West • Nov-12 Confidential Proprietary11 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
    12. 12. 12 • Steve West • Nov-12 Confidential Proprietary12 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)
    13. 13. 13 • Steve West • Nov-12 Confidential Proprietary13 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
    14. 14. 14 • Steve West • Nov-12 Confidential Proprietary14 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
    15. 15. 15 • Steve West • Nov-12 Confidential Proprietary15 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
    16. 16. 16 • Steve West • Nov-12 Confidential Proprietary16 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
    17. 17. 17 • Steve West • Nov-12 Confidential Proprietary17 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
    18. 18. 18 • Steve West • Nov-12 Confidential Proprietary18 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
    19. 19. 19 • Steve West • Nov-12 Confidential Proprietary19 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
    20. 20. 20 • Steve West • Nov-12 Confidential Proprietary20 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
    21. 21. 21 • Steve West • Nov-12 Confidential Proprietary21 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 NSIC2030B 120 V, 30 mA Constant Current Regulator & LED Driver NSIC2050B 120 V, 50 mA Constant Current Regulator & LED Driver
    22. 22. 22 • Steve West • Nov-12 Confidential Proprietary22 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%
    23. 23. 23 • Steve West • Nov-12 Confidential Proprietary23 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
    24. 24. 24 • Steve West • Nov-12 Confidential Proprietary24 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
    25. 25. 25 • Steve West • Nov-12 Confidential Proprietary25 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
    26. 26. 26 • Steve West • Nov-12 Confidential Proprietary26 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
    27. 27. 27 • Steve West • Nov-12 Confidential Proprietary27 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
    28. 28. 28 • Steve West • Nov-12 Confidential Proprietary28 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
    29. 29. 29 • Steve West • Nov-12 Confidential Proprietary29 Current Regulation (150 V LED)
    30. 30. 30 • Steve West • Nov-12 Confidential Proprietary30 Efficiency at Vf=150 V, 25 mA (nom)
    31. 31. 31 • Steve West • Nov-12 Confidential Proprietary31 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
    32. 32. 32 • Steve West • Nov-12 Confidential Proprietary32 Performance Highlights 125 ms Startup Time
    33. 33. 33 • Steve West • Nov-12 Confidential Proprietary33 HiPF Buck Application Schematic
    34. 34. 34 • Steve West • Nov-12 Confidential Proprietary34 Design Guide Worksheet Tool
    35. 35. 35 • Steve West • Nov-12 Confidential Proprietary35 Example of NCL30002 Driver Design NCL30002 Demo Board
    36. 36. 36 • Steve West • Nov-12 Confidential Proprietary36 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
    37. 37. 37 • Steve West • Nov-12 Confidential Proprietary37 NCP1075 Boost Efficiency/Regulation Vout = 213 V (nom)
    38. 38. 38 • Steve West • Nov-12 Confidential Proprietary38 NCP1075 Power Factor/Harmonic Content Vout = 213 V (nom)
    39. 39. 39 • Steve West • Nov-12 Confidential Proprietary39 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
    40. 40. 40 • Steve West • Nov-12 Confidential Proprietary40 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
    41. 41. 41 • Steve West • Nov-12 Confidential Proprietary41 Appendix
    42. 42. 42 • Steve West • Nov-12 Confidential Proprietary42 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.
    43. 43. 43 • Steve West • Nov-12 Confidential Proprietary43 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
    44. 44. 44 • Steve West • Nov-12 Confidential Proprietary44 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
    45. 45. 45 • Steve West • Nov-12 Confidential Proprietary45 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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