1. LED
Lighting
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Harendra Vishwakarma

2. LED – LIGHT 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.
Light
“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

3. Light Emitting Diode -History

4. MultiChip

5. Structure of LED
LED Manufacturing Stages
The Wafer – The Substrate on which chip P-N
is grown. junction Electrical
Contacts
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.

6. K

7. Selection of LEDs
 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.
Trade-off Summary
Color Temperature* Efficacy
CRI* Efficacy
Heat Efficiency / Output
Heat Life / Durability

8. Availability of various shade of colours
3000 K 3500 K 6500 K
Appearance of similar product in different CCT Light

9. Reliability Greater Design Flexibility
 Long Life over 11 yrs (12 hrs a day  Various Colors available
operation)
 Instant On
 Lower Life Cycle Cost (Less wattages
gives more lumen & Longer life)  Dimming, & Intelligent control.
 Less Maintenance Cost  No IR and UV.
 Shock & Vibration Proof  Wide range of CCT and CRI
Efficient Technology Environmental friendly
 High efficiency  No Mercury
 Due to directional source. (Minimal  Less waste creation due to long
backward losses)
life.
 Due to High Lm/W of LED.
(Gradually increasing with technology)  Less carbon emission.
 Low Voltage

10. Comparison Between Various Light sources
Power 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 %

11. Comparison of Life of Various Light sources
Light Source Typical Typical Rated Lumen
System Life Depreciation @
Efficacy (Hrs) Rated Life
(lm/W)
Incandescent 10-18 750- 2000 10-15 %
Halogen 15-20 3,000-4,000 30%
Incandescent
CFL 35-60 8,000-10,000 30%
Linear Fluorescent 50-100 20,000 – 30,000 5- 10 %
(T5, T8)
Metal Halide 50-90 7,500 – 20,000 20%
White LED 5000K 60-100 50,000-100,000 30 %
Warm White LED 45-80 50,000-100,000 30%
3300K

12. LED Lamp & Luminaires
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
Simple Model of LED luminaire More Accurate model of LED luminaire

14. Illuminance
IESNA Definition: the areal density of the luminous flux incident at a point on a
surface.
Illuminance is calculated as the number of lumens (lm) per unit area.
Two common units used to measure illuminance are:
footcandles (fc) = lm/ft2
lux (lx) = lm/m2
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

15. 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 SDCM
No Color difference Hardly any color
visible 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).

17. • 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,

18. • 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

19. List of testing standard
. 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