PREPARED BY: UNDER THE SUPERVISION OF:

DEPARTMENT OF ELECTRICAL ENGINEERING

ER. ABHINAB KUMAR (ASSISTANT PROFESSOR)

RAHUL KUMARBACHELOR OF TECHNOLOGY ELECTRICAL ENGINEERING (3RD YEAR) ROLL NO:1473420034

A PRESENTATION ON LED TECHNOLOGY

RAJKIYA ENGINEERING COLLEGE BANDA

CONTENT•ABOUT SSL•INTRODUCTION•CURRENT TECHNOLOGY•CONSTRUCTION•HEAT ISSUES•LED COLOUR•PHOSPHOR TECHNOLOGY•SPECTRAL DISTRIBUTION OF WHITE LIGHT•LED MANUFACTURING STAGES•LEAD USEFUL CHARACTERICTICS•LEAD SYSTEM DESIGN•APPLICATIONS•CONTROLLABILITY•THE FUTURE•DISADVANTAGES•CONCLUSION

What is Solid State Lighting•Heating up bits of wireConventional Methods of converting electrical energy to light•Passing Electricity through gas at near vacuum•Passing Electricity through gas above atmospheric pressure

How About LED’s

•Passing Electricity through small amounts of crystalline solids•Solid State device Works well with other semiconductors•Initially used for panel indicators•Discovered in 1962 by Nick Holonyak•In 1963 he predicted white LEDS with 10X efficiency of Incandescent

Early LED colour•Initially red mass produced from 1969•GaAsP Gallium Arsenide Technologyproduced red, amber and yellow early green produced by IR and phosphor•GaAIA Gallium Aluminum Arsenide High brightness red LEDs from 1984

•InGaN Indium Gallium Nitride Technology produced blue and green•Allowed development of White LED

Current Technology

•Based on InGaN and A AnGaP•Many colours possible•Colour varies with growth temperature of active layer•Efficiency drops in Green•Different compositions behave differently•Reds and ambers have shorter life and greater colour shiftsBlues more stable

Construction of LEDs•Standard 5mm LED•Epoxy body sometimes coloured•Leads identified for polarity•Reflector maximises light output•Die, semiconductor that emits light

Construction of LEDs

•High output LEDs•Large die with reflector•Mounted to Slug heat sink•Leads exit to side clear of light path•Moulded lens gathers and directs light•Various distribution patterns•Many different packages

LED Colour

•Each type of LED emits light in a narrow band width•Good for saturated colour•Limited for RGB mixed white

White LEDs

•Fluorescence; uses blue die with phosphor•Combination of Blue from die and Yellow from phosphor givesvisual whiteColour not even across LEDWarmer colours less efficient

Phosphor technology

•Best is Itrium Aluminium Garnate Cerium•Produces broad spectrum yellow•90% efficient converting blue to yellow•Deficient in Red•Strontium Sulphide Europium•Produces increased red•Much less efficient•Can create pink tinge in 2700K range•Importance of even thickness Consistent colour•Match binning of phosphor with LED•Recent development of phosphor wafers or better control of thickness

Spectral Distribution of White

White Light LEDs

•Research goal to create white light directly from die•ZnSe (Zinc Selenide) is a candidate technology not high output•Development as Zinc Oxide nanostructure semiconductor RGB

LED Manufacturing Stages

•Reasons for product variation•The Wafer•The Die•The Package

The Wafer•Disk of the crystalline material that forms semiconductor•Grown on mineral substrate: EpitaxySaphire, Silicone Carbide 2” or 6” diameterAim to use 12” Silicone for economy•Tightly controlled conditions to achieve uniform result•First layer grown at 1000°C•Second at 700°C•Final at 1000° C•Risk of changes to middle layer Substrates flex•Varies thickness of layers•Process takes 5 to 6 hours

The Die•Wafer literally “diced” like carrots!•Dies “binned”•For colour (chromaticy)•For forward voltage•For output

Packaging•Connections made to die•Die inserted in package•Many dies in same package•Device tested for:forward voltagecolour (chromacity)lumen outputLEDs then Binned

Binning•Much discussed aspect of LEDs•At end of production line measurements madefraction of a seconddevice at room temperature 25°Cfully automated processFirst stage of quality control•Possibly the most importantaspects tested:ColourLumen OutputForward Voltage

Heat Issues•Temperature in die determines LED survival determines operating life determines light output determines efficiency•Higher the temperaturelower light outputlower the efficiency•Critical temperature much lower than conventional lamps•LED internal temperatures 100°C to 150°C absolute maximum depends on chip

LEDs Useful Characteristics‐• Electrically Efficient• Long Lifetime• Low radiated heat• Emit pure colors without filters (more efficient)• Intensity can be varied over operational range with littlespectral shift• Rapid on/off capability• Small size allows unprecedented flexibility in application• Rugged– Solid state– Not damaged by repeated on/off cycles– No fragile glass envelope• No hazardous materials (e.g. mercury)

LEDs Useful Characteristics‐‐Can Match Spectrum to Application

LEDs Useful Characteristics‐•Highly flexible Advanced Lighting Control Systems

HELIAC adaptive lighting system

LED System Design

“Standard” 5mm

Standard surface mount (SMT)‐

High power emitter types‐

Pre packaged high power‐ ‐arrays

LED System DesignOptics– Commercially available– Custom / application specific

•Diffusers•Lens•Collimators

•Remote Phosphor

LED Mechanical Components & Configuration

Power and signaldistribution

Arrays of LEDs(actively or passivelycooled

Optics and protectionmechanisms

Control box(many configurationspossible)

APPLICATIONS•LED Plant Lighting in Space

•System Configuration; Overhead Bars

• Large Sole Source Lighting Arrays

• IN DOMESTIC USES

• IN AUTOMOBILES

• FOR INDICATION

LED Plant Lighting in Space

Astroculture 4‐1994First LED plantlighting in space

Veggie 01‐2014

System Configuration; Overhead Bars

Large Sole Source Lighting Arrays

Controllability

•LEDs easy to control - they arean electronic component!•Facades of light easy to doImagery allows architecture tochange day and night•Reactive and interactivesurfaces, walls and ceilings•LEDs deliver colour easily andefficiently compared withother light sources

The Future•Field of light products much more likely to be successful•optimizes use of LED and existing backlight technology•opens possibilities for fittings not to be rectangular or circular•no longer are fitting sizes restricted by set dimensions of lamps•First product recall, High efficiency LEDs recalled from fittings manufacturers•Production halted for 4 months•Line voltage LEDs•Seol semiconductor Acriche2W & 4W 120V and 230V warm and cool white30LmW to 40 LmW headline efficacy•No transformer losses•Simplified Wiring

The Future•Multi colour chips on same wafer - White by color mixingComplex circuits on chip - •Zinc Oxide Nanotechnology Semiconductor•LED materials can also produce energy from light•LED detectors / emitters•Development of Photovoltaics using InGaN junctions

Environmental Issues•Price per lumen of LED exceeds all other light sources•Revenues consumed by continuous development•Additional cost must be argued on basis of:-low maintenancelow energy in useSystem has finite lifeNot always determined before installation•Whole system will require replacement at end of life•- Issues with WEEE for disposal and re-cycling

DISADVANTAGES• LEDs are currently more expensive, price per lumen, on an initial capital cost basis, than more conventional lighting technologies.

• LED performance largely depends on the ambient temperature of the operatingenvironment. Over-driving the LED in high ambient temperatures may result inoverheating of the LED package, eventually leading to device failure. Adequateheat-sinking is required to maintain long life

• LEDs must be supplied with the correct current. This can involve series resistorsor current-regulated power supplies

Conclusion•LEDs increasingly common in lighting applications•They remain the most complex light-source to design andspecify•Manufacturers are guardians of knowledge•Big players potential to monopolize design to installation•Professional Lighting Design community must learn more•Personal research and demanding information from suppliers•Professionals must determine the suitable light-source for everyapplication•LEDs will never be the universal light-source for all applications

Thank you

AND YOU HAVE FUN WITH LIGHT!

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