LLEEDD LightingLightingSave Energy Save Your moneySave Energy Save Your money

Harendra Vishwakarma

LEDLED – LIGHT EMITTING DIODELIGHT EMITTING DIODE

LED, a semiconductor diode which when operated in forward biased

(switched on), electrons are able to recombine with holes within the device,

releasing energy in the form of photons. This effect is called

electroluminescence.

The wavelength of the light emitted, and therefore its color, depends on the

band gap energy (Eg) of the materials forming the p-n junction.LightLight “The radiant energy that is capable of excite human retina and

creating visual sensation.” Light by definition connotes Electromagnetic radiation that has a

emission in visible part of spectrum (wavelength in the range of 380 nm to about 780 nm)

Visible

Light 380

nm –

780 nm

Light Emitting Diode -HistoryLight Emitting Diode -History

MultiChip

Structure of LEDStructure of LED

P-N junction Electrical

Contacts

LED Manufacturing StagesLED Manufacturing Stages

The Wafer – The Substrate on which chip is grown.

The Die – P-N junction between p-type doped semiconductor and n-type doped semiconductor.

The Package – Enclosed structure of die in the epoxy or plastic case with appropriate phosphor for colour and lenses for view angle determination.

K

Binning: Variation of color in LED Batch

Color Temperature: A measurement of the color of light radiated by a black body while it is being heated. This measurement is expressed terms of absolute scale, or degrees Kelvin. Lower Kelvin temperatures such as 2400K are red; higher temperatures as 9300K are blue. Neutral temperature is white, at 6504K.

Forward Voltage

Colour

Color Rendering Index : To help indicate how colors will appear under different light sources,

Lumen Output

Lumen output is in mcd for smaller packages and lumen for power LEDs.

Selection of LEDsSelection of LEDs

Trade-off SummaryColor Temperature* Efficacy

CRI* Efficacy

Heat Efficiency / Output

Heat Life / Durability

3000 K 3500 K 6500 K

Availability of various shade of colours

Appearance of similar product in different CCT Light

Reliability Long Life over 11 yrs (12 hrs a

day operation)

Lower Life Cycle Cost (Less

wattages gives more lumen & Longer life)

Less Maintenance Cost

Shock & Vibration Proof

Greater Design

Flexibility Various Colors available

Instant On

Dimming, & Intelligent control.

No IR and UV.

Wide range of CCT and CRIEnvironmental

friendlyEfficient Technology High efficiency

Due to directional source. (Minimal backward losses)

Due to High Lm/W of LED. (Gradually increasing with technology)

Low Voltage

No Mercury

Less waste creation due to

long life.

Less carbon emission.

Power Consumption for White Light SourcePower Consumption for White Light Source

Incandescent Fluorescent MH LED

Visible Light 7.5 % 21 % 27 % 15-25 %

Infrared 73.3 % 37 % 17 % ~ 0 %

Ultraviolet 0 % 0 % 19 % 0 %

Total Radiant Energy 80.8 % 58 % 63 % 15-25 %

Heat (Conduction + Convection)

19.2 % 42 % 41 % 75-85 %

Total 100 % 100 % 100 % 100 %

Comparison Between Various Light sourcesComparison Between Various Light sources

Light Source Typical System Efficacy (lm/W)

Typical Rated Life

(Hrs)

Lumen Depreciation @

Rated Life

Incandescent 10-18 750- 2000 10-15 %

Halogen Incandescent

15-20 3,000-4,000 30%

CFL 35-60 8,000-10,000 30%

Linear Fluorescent (T5, T8)

50-100 20,000 – 30,000

5- 10 %

Metal Halide 50-90 7,500 – 20,000 20%

White LED 5000K 60-100 50,000-100,000

30 %

Warm White LED 3300K

45-80 50,000-100,000

30%

Comparison of Life of Various Light sourcesComparison of Life of Various Light sources

A luminaire is a lighting fixture complete with the light source or lamp, the

reflector for directing the light, an aperture (with or without a lens), the outer

shell or housing for lamp alignment and protection, an electrical ballast and/or

power supply (if required), and connection to a power source, and usually a light

socket to hold the lamp and allow for its replacement

LED Lamp & LuminairesLED Lamp & Luminaires

Simple Model of LED luminaire More Accurate model of LED

luminaire

Two common units used to measure illuminance are:footcandles (fc) = lm/ft2

lux (lx) = lm/m2

Illuminance

IESNA Definition: the areal density of the luminous flux incident at a point on asurface.Illuminance is calculated as the number of lumens (lm) per unit area.

Luminance

IESNA Definition: the quotient of the luminous flux at an element of the surface surrounding the point, and propagated in directions defined by an elementary cone containing the given direction, by the product of the solid angle of the cone and the area of the orthogonal projection of the element of the surface on a plane perpendicular to the given direction.

Luminance is the photometric quantity most closely associated with one's perception of brightness. It usually refers to the amount of light that reaches the eye of the observer measured in units of luminous intensity (candelas) per unit area (m2).

IESNA – ILLUMINATION ENGINEERING SOCIETY OF NORTH AMERICA

MacAdam ellipses and SDCM

Dimension of a MacAdam ellipse is given by the so called Standard Deviation of Color Matching (SDCM), SDCM characterises the quality of color differences

1 SDCM 2-3 SDCM 4 SDCMNo Color difference

visibleHardly any color

difference possible Color Difference Visible

Spectral Power Distribution

IESNA Definition: A pictorial representation of the radiant power emitted by a light source at each wavelength or band of wavelengths in the visible region of the electromagnetic spectrum (360 to 770 nanometers).

• Optical instruments:– Integrating Sphere – Lumen measurement of

luminaire, Chromaticity, Color Rendering Index,

Dominant Wavelength, FWHM,

– Lux meter – illuminance (Lux value , Ft-Cd)

measurement at specific distance.

– Luminance Meter –Luminance measurements at

surface (Cd/ m2)

– Spectroradiometer – Exact Color and spectrum

(W/ m2 –sr-nm)

– Goniophotometer/ Goniospectrometer -

Generating IES files for luminaire, polar curves,

• Thermal Measurements:– Thermocouples, (Contact mode method) –

Temperature profile of LED module and

Luminaire with respect to room temperature,

Thermocouple needs to be <+/-1.1C or +/-

0.4% accuracy for Case Temperature during

test

– Infra-red pyrometers, (Non-contact mode

method)– Junction temperature

measurement, heat sink temperature.

– Digital Temperature Meter - Temperature

profile of LED Luminaire

. ANSI/NEMA Standards to SSL products - •C78.377-2008 - Specifications for the Chromaticity of Solid State Lighting Products•NEMA SSL-1† Power Supply - Will specify operational characteristics and electrical safety of SSL power supplies and drivers. •C82.77-2002 - Harmonic Emission Limits – Related Power Quality Requirements for Lighting

IESNA Documents – •TM-16-05 - IESNA Technical Memorandum on Light Emitting Diode (LED) Sources and Systems.•RP-16-05 - Addendum a Nomenclature and Definitions for Illuminating Engineering.•LM-79-08 - IESNA Approved Method for the Electrical and Photometric Measurements of Solid-State Lighting Products,•LM-80-08 - IESNA Approved Method for Measuring Lumen Maintenance of LED Light Sources.•TM-21† -Lumen Depreciation Lifetime Estimation Method for LED Light.•LM-80. LM-XX† Method for the Measurements of High-Power LEDs

List of testing standard