Basics of Backlights VS 12th June 2007 Holger Dziadek 1 VS CCFL (Cold Cathode Fluorescence Lamp) Edge-Light Direct Backlight LED (Lighting Emiting Diode) Edge-Light Direct Backlight White or RGB EL (Electro Luminance) Direct Backlight 12th June 2007 Holger Dziadek 2 Objectives of the Course VS White LED Technology – Types of white LEDs Design Advantages of the Technology – Life – Efficiency Design Considerations – Color matching – Heat dissipation – Cost Range of Products Available Today 12th June 2007 Holger Dziadek 3 White Through History VS Progress in lighting 12th June 2007 Holger Dziadek 4 Progression of White Lighting 12th June 2007 Holger Dziadek VS 5 Specifying LEDs (in general) VS Type (3mm, 5mm, High Flux, etc.) R-G-B with different LED’s White LED’s 12th June 2007 Holger Dziadek 6 VS Definitions—Flux Radiometric Flux to Luminous Flux Photopic Eye Response 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 400 450 500 550 600 650 700 Wavelength (nm) 12th June 2007 Holger Dziadek 7 VS Definitions - Color White LED Range 12th June 2007 Holger Dziadek 8 VS Definition – White Correlated Color Temperature (CCT) 12th June 2007 Holger Dziadek 9 Definitions – Forward Voltage VS Forward Voltage Vf is roughly equal to the bandgap energy of the LED semiconductor divided by the elementary charge Vf = Eg / q where q =1.6 x 10-19 coulombs Output Intensity of typical high brightness LEDs is dependent on the Forward Current If 12th June 2007 Holger Dziadek 10 VS Construction Difference (5mm versus High Flux LEDs) Typical construction for a 5mm LED Typical construction for a High Flux LED Typical Flux = 3 lm Typical Flux > 30 lm Number of LEDs to equal the output of a 60W incandescent light bulb = 200 12th June 2007 Number of LEDs to equal the output of a 60W incandescent light bulb < 20 Holger Dziadek 11 VS AlInGaP Red, Red-Orange Yellow AlInGaN Green, Blue, White Group XIII Group XIV Group XV 5 6 7 B C N Boron 10.811 Carbon 12.0107 Nitrogen 14.006 13 14 15 Al Si P Aluminum 126.981 Silicon 28.0955 Phosphorus 30.973 31 32 33 Ga Ge As Gallium 69.723 Germanium 72.61 Arsenic 74.921 49 50 51 In Sn Sb Indium 114.818 Tin 118.710 Antimony 121.760 Substrates Silicon Carbide (SiC) Sapphire (Al2O3) Base Elements P-Type Dopants N-Type Dopants 12th June 2007 Holger Dziadek 12 How do you make LEDs? VS Lens Materials 3 mm and 5 mm Epoxy lens Bad expansion coefficient (stresses bond wire) – Yellows – Degradation blue/UV – HIGH FLUX COC, other hard plastic lens with silicone gel – Plastic with silicone gel – Not reflow solderable Silicone polymer lens with silicone gel – Robust for reflow, lead free temperature 260C – Better moisture handling – Susceptible to dirt and scratches Glass lens with silicone gel – More robust – Higher cost 12th June 2007 Holger Dziadek 13 How do you make LEDs? VS Substrate Materials Sapphire (Al2O3) – Lower cost (estimated at $3/cm2) – More transparent (more light output) – Low thermal conductivity (40 W/m/K) Silicon Carbide (SiC) – Higher cost (estimated at $12/cm2) – Better ESD protection – High thermal conductivity (350-490 W/m/K) 12th June 2007 Holger Dziadek 14 How do you make a White LED? VS RGB Method Mixing light from red, green and blue LEDs (either discrete or combined in one package) can produce white light 12th June 2007 Holger Dziadek 15 VS How do you make a White LED? Visible LED Pump + Phosphor Method Blue LED + YAG Cool White Blue LED + YAG + Other phosphor (red, green, etc.) Warm White UV LED Pump + Phosphor Method UV LED + Red phosphor + Green phosphor + Blue phosphor Luxeon K2 12th June 2007 Holger Dziadek 16 How do you make a White LED? VS (Blue + Phosphor) VS (Red + Green + Blue) Warm White (3500K) Blue + Phosphor 100 lumens 34 lumens/watt 2.92 watts Blue 2.3 13.4 0.17 Green 66.7 38.9 1.71 Red 30.7 29.9 1.03 Total 100 lumens n/a lumens/watt 2.91 watts 8E+12 7E+12 50 6E+12 Radiometric Power (a.u.) Radiometric Power (a.u.) 60 40 5E+12 4E+12 30 3E+12 20 2E+12 10 0 400 1E+12 0 450 500 550 600 650 700 Wavelength (nm) 12th June 2007 Holger Dziadek 17 VS How do you make a White LED? Phosphor Deposition Examples Lumileds Lumileds Seoul Semiconductor Osram Cree 12th June 2007 Nichia Holger Dziadek 18 How do you make a White LED? VS Which method is better for making white? Disadvantages Advantages RGB • Color can be changed dynamically • As a luminance source, millions of colors can be produced • Highest theoretical luminous efficiency of all three methods • No UV output • Color can shift due to aging and temperature • Requires more sophisticated electronics • Poor color rendition • Fixture efficiency drop caused by color mixing 12th June 2007 Blue + Phosphor UV + Phosphor • High theoretical luminous • Good color uniformity efficiency • Simple driver electronics • Can provide color • Potential for limited tint temperatures between 3200 K variation (warm white) and 10,000 K • Eliminates the pump color (cool white) variation; only phosphor • No UV output variation • Potential to create variations in tint • Must be controlled using optics and binning Holger Dziadek • Lowest luminous efficiency • Shorter life • Clouding of the epoxy (UV packaging problems) • New phosphors necessary 19 How long do light sources last? VS Time to change the lightbulb! The sun Candle Oil Lamp Incandescent (Bulb) Fluorescent (CCFL) Mercury Vapor Sodium Vapor Metal Halide 5mm LEDs High Flux LEDs 12th June 2007 >4.5 billion years (so far) <12 hours <24 hours 1k-1.5k hours 25k-60k hours What is End of Life for some 10k-20k hours illumination 24k hours sources? 20k-30k hours <10k hours >20k hours Holger Dziadek 20 How long do light sources last? VS LED Lifetime How long do they last? 12th June 2007 Holger Dziadek 21 How long do light sources last? VS What do we mean by Lifetime? Traditionally Lifetime was the time it took for 50% of the population of incandescent bulbs to fail Many light sources don’t fail catastrophically—Define EOL by reduction in light output from initial values for example 70% or 50% of initial value Under what conditions do we measure lifetime? High Flux LED 5mm LED Incandescent 12th June 2007 Holger Dziadek 22 VS How long to light sources last? Lab60Data on 5mm LED Lifetimes 30 mA, LED PCB temp of 100 C 50 20 mA, LED PCB temp of 80 C 10 mA, LED PCB temp of 40 C Intensity (candelas) 40 30 20 10 0 0 5000 10000 15000 20000 25000 30000 35000 Time (Hours) 12th June 2007 Holger Dziadek 23 Lifetime (half-life) shortens with increasing Temperature and Drive Current VS Data extracted from page 11 of LW Z3SG data sheet. Examples OSRAM 12th June 2007 Holger Dziadek 24 Generic white LED lifetime vs. Temperature VS Temperature Solderpoint Power TOPLED® (LW_E6SG) @ fixed If = 30 mA 3 103* (*: Ta = 85°C) 2 65 45 1 0 20 40 60 80 100 Lifetime [k h] 12th June 2007 Holger Dziadek 25 Thermal Management Issues 12th June 2007 Holger Dziadek VS 26 Thermal Management Issues VS Which heat sink do I need? 40 °C/W 12th June 2007 or Holger Dziadek 0.4 ° C/W 27 Manufacturers Examined VS Cree – XLamp Series LumiLeds – Luxeon Series – K2 Series Nichia – Jupiter Series Osram – Golden Dragon Series Seoul Semiconductor – Z-Power Series 12th June 2007 Holger Dziadek 28 VS Temperature LED Light Guide Lost Distance Cable PCB Cooling Fin CCFL Light Guide Hot Connector 12th June 2007 +25 C +40 C Reflector Holger Dziadek 29 VS Thermal Management Issues Calculating Safe Junction Temperatures LED LED LED Thermal Epoxy Thermal Epoxy Thermal Epoxy Metal Core PC Board Heat Sink TJunction = TA + ( PLED ) ⋅ ( RΘ LED ) + ( PLEDs ) ⋅ ( RΘ Heat sin k ) 12th June 2007 Holger Dziadek 30 VS Thermal Management Issues Increasing from 1W to 3W LEDs Operating temperature of +25°C 15 °C/W 15 °C/W 15 °C/W 6 °C/W 6 °C/W 6 °C/W 0.1 °C/W 10 ° C/W TJunction = 25°C + (1W ) ⋅ (21°C / W ) + (3W ) ⋅ (10.1°C / W ) TJunction = 76.3°C TJunction = 25°C + (3W ) ⋅ (19°C / W ) + (9W ) ⋅ (10.1°C / W ) TJunction = 172.9°C!!! 12th June 2007 Holger Dziadek 31 VS Thermal Management Issues Increasing from 1W to 3W LEDs Operating temperature of +60°C 15 °C/W 15 °C/W 15 °C/W 6 °C/W 6 °C/W 6 °C/W 0.1 °C/W 10 ° C/W TJunction = 60°C + (1W ) ⋅ (21°C / W ) + (3W ) ⋅ (10.1°C / W ) TJunction = 111,3°C TJunction = 60°C + (3W ) ⋅ (19°C / W ) + (9W ) ⋅ (10.1°C / W ) TJunction = 207,9°C!!! 12th June 2007 Holger Dziadek 32 Datasheet Lumens vs Actual Lumens VS 1-Watt LEDs, 25 °C ambient temperature Datasheet: 45 Lumens at a 25 °C die temperature Dynamic resistance: 1 Ω Temperature coefficient of Vf: -2.0 mV/ °C 15 °C/W thermal resistance for the LED 6 °C/W thermal resistance for the thermal epoxy and PCB dielectric 10 °C/W for the heatsink, board interface, etc. Relative Luminous Flux 120 100 80 60 40 20 0 0 20 40 60 80 100 120 Die Junction Temperature (°C) 12th June 2007 Holger Dziadek 33 Cool White LED Comparison Osram LW W5SG Cool Osram ZW W5SG Cool Osram LW W5SN Cool Osram LW W5SM Cool Osram LEW E3A Cool Osram LEW E3B Cool Osram LEW E2A Cool Osram LEW E2B Cool Lumileds LXHL-PW01 Cool Lumileds LXHL-DW01 Cool Lumileds LXHL-BW02 Cool Lumileds LXHL-PW09 Cool Lumileds LXHL-DW09 Cool Lumileds LXHL-PW03 Cool Lumileds LXK2-PW etc Cool Nichia NCCW002, etc Cool Nichia NS6W083 Cool Cree XL7090 Cool Cree 3XL7090 Cool Cree XL7090XR Cool Seoul Semi W10190 Cool Seoul Semi W10290 Cool Seoul Semi W10490 Cool Cotco LD-700AWN1-70 Cool 12th June 2007 Thermal Viewing Typical Typical Typical RestistTypical Lumens Dice Angle 350 500 700 1000 1400 1500 Current Voltage Power ance °C/W mA Vf W # Degees mA mA mA mA mA mA 1 120 21-39 41 350 3.8 1.3 9 1 120 33-71 60 350 3.2 1.1 15 1 120 52-97 700 3.8 2.7 8 1 120 64 350 3.2 1.1 15 6 120 300 700 22.5 15.8 3.6 6 120 420 700 22.5 15.8 3.6 4 120 200 700 15 10.5 5 4 120 280 700 15 10.5 5 1 120 45 350 3.42 1.2 15 1 Side-emit 40.5 350 3.42 1.2 15 1 Batwing 45 350 3.42 1.2 15 1 120 65 80 700 3.7 2.6 13 1 Side-emit 58 70 700 3.7 2.6 13 4 150 87.4 700 6.84 4.8 8 1 150 52.5 87.5 110 135 1000 3.72 3.7 9 1 35,70,120 42 ? 350 3.7 1.3 17 4 120 60 ? 350 3.6 1.3 10 1 100 52 ? 350 3.5 1.2 17 1 100 76 700 4 2.8 17 1 100 53.5 ? 350 3.5 1.2 8 1 70,110 52 350 3.5 1.2 8 2 70,110 103 700 3.5 2.5 6 4 70,110 178 1400 3.5 4.9 4 1 70 27 350 3.6 1.3 15 Holger Dziadek VS Rise LED Max Only Junction °C °C 12 125 17 125 21 135 17 125 57 150 57 125 53 150 53 125 18 135 18 135 18 135 34 135 34 135 38 135 33 150 22 105 13 120 21 125 48 145 10 145 10 125 15 125 20 125 19 125 CRI 80 80 80 80 80 80 80 80 70 70 70 70 70 70 70 80 80 75 75 75 70 70 70 34 White is White is White VS Binning Issues Osram White Binning 12th June 2007 Holger Dziadek 35 White is White is White VS Binning Issues Seoul White Binning 12th June 2007 Holger Dziadek 36 VS Chromaticity Binning Comparison 0.5 Osram Cool Osram Warm Lumileds Cool 0.45 Lumileds Warm Nichia Cool 0.4 Nichia Warm y Cree XL Cree XR 0.35 2500 Kelvin 15000 Kelvin Seoul Cool Seoul Warm 0.3 Cotco Cool Blackbody 0.25 0.2 0.2 12th June 2007 0.25 0.3 0.35 0.4 x Holger Dziadek 0.45 0.5 0.55 0.6 37 VS Spectral and Chromaticity Measurements 0.5 2.00E-03 0.45 1.80E-03 0.4 Y 0.35 1.60E-03 Luminous Flux (a.u.) 0.3 1.40E-03 0.25 0.2 1.20E-03 0.2 0.3 0.4 X 0.5 0.6 CreeXL7090WHT 1.8E+13 CreeXL7090WW SeoulW32180 SeoulN32180 1.6E+13 LumiledsPW12 K2 LumiledsLXHL-BL03 1.4E+13 NichiaNCCW022 NichiaNCCL023 1.2E+13 OsramLW W5SG 3500k Blackbody 1E+13 1.00E-03 8E+12 8.00E-04 6E+12 6.00E-04 4E+12 4.00E-04 2E+12 2.00E-04 0.00E+00 400 12th June 2007 0 450 500 550 600 Wavelength (nm) Holger Dziadek 650 700 750 38 VS CCT Change with Time 12000 Conditions: 350 mA 25C Ambient Correlated Color Temp (CCT K) 11000 10000 Supplier 1 Supplier 1 Supplier 1 Supplier 2 Supplier 3 Supplier 4 Supplier 5 Supplier 6 Supplier 6 9000 8000 7000 6000 5000 4000 3000 2000 0 12th June 2007 500 1000 1500 Time (hours) Holger Dziadek 2000 39 VS CCT Change with Time 12000 Conditions: 500 mA 25C Ambient Correlated Color Temp (CCT K) 11000 10000 Supplier 1 Supplier 1 Supplier 1 Supplier 2 Supplier 3 Supplier 4 Supplier 4 Supplier 4 Supplier 5 Supplier 6 9000 8000 7000 6000 5000 4000 3000 2000 0 12th June 2007 500 1000 Time (hours) Holger Dziadek 1500 2000 40 VS CCT Change with Time 12000 Conditions: 350 mA 75C Ambient Correlated Color Temp (CCT K) 11000 10000 Supplier 1 Supplier 1 Supplier 1 Supplier 2 Supplier 3 Supplier 4 Supplier 5 Supplier 6 Supplier 6 9000 8000 7000 6000 5000 4000 3000 2000 0 12th June 2007 500 1000 Time (hours) Holger Dziadek 1500 2000 41 CCT Change with Time VS 0.0006 480 hours 960 hours 1176 hours 1464 hours 1632 hours 1824 hours Luminous Flux (a.u.) 0.0005 0.0004 0.0003 0.0002 0.0001 0 400 12th June 2007 450 500 550 600 Wavelength (nm) Holger Dziadek 650 700 750 42 VS Luminous Flux Change with Time 120% Conditions: 350 mA 25C Ambient Relative Luminous Flux (%) 100% Supplier 1 Supplier 1 Supplier 1 Supplier 2 Supplier 3 Supplier 4 Supplier 5 Supplier 6 Supplier 6 80% 60% 40% 20% 0% 0 12th June 2007 500 1000 Time (hours) Holger Dziadek 1500 2000 43 VS Luminous Flux Change with Time 120% Conditions: 500 mA 25C Ambient Relative Luminous Flux (%) 100% Supplier 1 Supplier 1 Supplier 1 Supplier 2 Supplier 3 Supplier 4 Supplier 4 Supplier 4 Supplier 5 Supplier 6 80% 60% Outliers are likely from measurement error 40% 20% 0% 0 12th June 2007 500 1000 Time (hours) Holger Dziadek 1500 2000 44 VS Luminous Flux Change with Time 120% Conditions: 350 mA 75C Ambient Relative Luminous Flux (%) 100% Supplier 1 Supplier 1 Supplier 1 Supplier 2 Supplier 3 Supplier 4 Supplier 5 Supplier 6 Supplier 6 80% 60% 40% 20% 0% 0 12th June 2007 500 1000 1500 Time (hours) Holger Dziadek 2000 45 The Cost of Light Lamp Type Incandescent Flourescent High Pressure Mercury High Pressure Sodium Metal Halide W hite LED (Luxeon K2) W atts Life 60 32 250 250 400 5 1.000 24.000 24.000 24.000 20.000 50.000 Cost of Light = Where 12th June 2007 VS Initial Lumens 850 3.000 11.000 28.000 36.000 100 Maintained Lumens 850 2.900 8.500 27.000 24.000 75 [ p + h ] / L + [W x R] F Price $0,90 $1,50 $21,00 $27,00 $70,00 $3,50 Luminous Efficiency 14 91 34 108 60 15 klm/$ $/Mlmh 0,94 2,00 0,52 1,04 0,51 0,03 $12,82 $1,18 $3,06 $0,97 $1,82 $8,67 (in $ / Mlm-hr) p is the lamp price (in cents) h is the labor cost to replace lamp (in cents) assumed to be 400¢ L is the lamp life (in hours) F is the lamp flux output (in lumens) W is the lamp input power (in watts) R is the energy cost (in cents/kW-hr) assumed to be 10¢ Holger Dziadek 46 Luminous Efficiency Improvement Trends 12th June 2007 Holger Dziadek VS 47 VS CCFL – Light Intensity Light Guide Light Hot Reflector Connector Relative Intensity (%) 100 80 60 40 20 0 0 20 40 60 80 100 Length of CCFL (mm) 12th June 2007 Holger Dziadek 48 LED – On The Side VS overexposed Area 12th June 2007 Holger Dziadek 49 VS LED – Light Intensity Light Guide Lost Distance Cable PCB Cooling Fin underexposed Area 12th June 2007 overexposed Area Holger Dziadek 50 VS LED – Backside LCD DBEF-Film BEF-Film Bulk Diffuser PMMA Plate Cable PCB Cooling Fin overexposed Area underexposed Area 12th June 2007 Holger Dziadek 51 VS White LED Trends 60 50 20 40 15 30 10 20 5 0 2002 12th June 2007 10 2003 2004 2005 Year Holger Dziadek 2006 Luminous Efficiency (lumens/watt) White Light Cost (Cents/Lumen) 25 0 2007 52 VS Advantage vs Disadvantage Issue CCFL LED ++ -- Homogeneous of Luminance + - Dimmable - ++ Lifetime@-30°C -- ++ Lifetime@0°C + ++ Lifetime@+25°C ++ + Lifetime@+60°C ++ -- Lifetime@+85°C ++ --- Environmental -- + Color Stabilization ++ + + + ++ - - + -- + Useable for Ex-Protected Area - ++ Medicine Application + ++ ++ - Size Brightness Stabilization Lost Temperature EMI Driving Voltage Price of System 12th June 2007 Holger Dziadek Note very good for automotive very bad for automotive CCFL mercury is very low For the same brightness approx. +20% 53 LED-Converter vs Resistor VS Examples for three HBLEDs with resistor R-limit = (Vin - (3 * Vfwd)) / Ifwd = (12V - (3 * 3.0V)) / 0.5A = 6 ohms P-limit = Ifwd2 * R-limit = 0.52 * 6 = 1.5 Watts P LEDs = 3 * Vfwd * Ifwd = 3 * 3.0V * 0.5A = 4.5 Watts Efficiency = PLEDs / (PLEDs + Plimit = 4.5W/ (4.5W + 1.5W) = 75% Not too impressive! Ifwd = (Vin - (3 * Vfwd)) / Rseries = (11.4V - (3 * 3.0V) / 6 ohms = 0.4 Amps Delta Vin = +/-5% variation of the +12V power supply will yield a +/- 20% variation in LED current — and therefore in LED brightness and life time. Of course, this variation could be reduced by increasing the voltage across the dropping resistor, but this would make the electrical efficiency only worse. 12th June 2007 Holger Dziadek 54 LED-Converter vs Resistor VS Examples for three HBLEDs with Converter R-limit = (Vin - (3 * Vfwd)) / Ifwd = (12V - (3 * 3.0V)) / 0.5A = 6 ohms P-limit = Ifwd2 * R-limit = 0.52 * 6 = 1.5 Watts P LEDs = 3 * Vfwd * Ifwd = 3 * 3.0V * 0.5A = 4.5 Watts Efficiency = Converter = >89% impressive! Ifwd = (Vin - (3 * Vfwd)) / Rseries = (11.4V - (3 * 3.0V) / 6 ohms = 0.4 Amps Delta Vin = +/-5% variation of the +12V power supply will yield a +/- 0% variation in LED current !! 12th June 2007 Holger Dziadek 55 VS LED-Converter Power Systems Converter Data sheet PS-LD0609-01 12th June 2007 Holger Dziadek 56 VS LED-Converter Power Systems Converter Data sheet PS-LD0101-01 12th June 2007 Holger Dziadek 57 Advantage vs Disadvantage VS LED and CCFL will life in harmony together. Both technologies have advantages and disadvantages. Our all customer need to decide what they need and want. Our job is to explain them the technologies. Good success. 12th June 2007 Holger Dziadek 58