Electrical systems design and Estimation KTU 2019 Scheme Notes on LED PPT notes

1. ELECTRICAL SYSTEMS
DESIGN &
ESTIMATION
EET402 | 2.2
LED – LIGHT EMITTING DIODE

2. LED – LIGHT EMITTING DIODE
• Light emitting Diodes or LEDs are
semiconductor devices that convert electrical
energy to light energy when operated in a
forward biased direction.
• They emit a narrow bandwidth of either
 visible light at different coloured wavelengths
 Invisible infra-red light (remote control
applications)
 laser type light
• Specialized type of PN Junction diode, made from
a very thin layer of fairly heavily doped
semiconductor material.

5. • PN Junction Diode
• Very thin layer of fairly heavily doped
semiconductor material.
• PN junction is surrounded by a transparent, hard
plastic epoxy resin hemispherical shell that
protects it from both vibration and shock.
• Some LEDs have rectangular or cylindrical
shaped construction that has a flat surface on top
• Cathode terminal is identified by:
 Either a notch
 Or by one of the leads being shorter than the
other (the anode)
Constructional Details of LED

8. • The diode has a valence band and a conduction
band.
• There are electrons in the conduction band and
holes in the valence band.
• When the diode is forward biased, electrons from
the conduction band recombine with the holes in
the valence band.
• This release energy to produce photons.
• The photons emit a monochromatic (single
colour) of light.
• LED has a thin of layer of semiconductor
material. So, these photons can leave the
junction and radiate away. This produces a
Working

9. • A large exposed surface area on one layer of the
semiconductive material permits the photons to
be emitted as visible light. This process, called
Electroluminescence.

10. LEDs & Their Colour
• Gallium Arsenide (GaAs) – infra-red
• Gallium Arsenide Phosphide (GaAsP) – red to infra-red,
orange
• Aluminium Gallium Arsenide Phosphide (AlGaAsP) – high-
brightness red, orange-red. Orange and yellow
• Gallium Phosphide (GaP) – red, yellow and green
• Aluminium Gallium Phosphide (AlGaP) – green
• Gallium Nitride (GaN) – green, emerald green
• Gallium Indium Nitride (GaInN) – near ultraviolet. Bluish-
green and blue
• Silicon Carbide (SiC) – blue
• Zinc Selenide (ZnSe) – blue
• Aluminium Gallium Nitride (AlGaN) – ultraviolet

11. RGB LEDs

12. RGB LEDs

13. Benefits of LED lamps over
other luminaires
• Normal incandescent lamps generate large
amounts of heat when illuminated. LEDs produce a
“cold” form of generation of light
• High efficiency – Most of the generated energy
radiates away within the visible spectrum
• They can be extremely small (solid-state devices)
• Durable
• Provide much longer lamp life (up to 50,000 hours)
than normal light sources. 60% longer life than
average long-life sodium-vapour commercial
luminaire
• LEDs does not contain UV component, so it does
not attract insects. Major advantage in exterior

14. Benefits of LED lamps over
other luminaires
• Estimated 80-90% energy efficiency
ENERGY EFFICIENT
• Offer instant lighting
• Brighten up immediately when powered
• Frequent ON/OFF switching of conventional
other luminaires can reduce their operational
life expectancy. But LEDs can be switched ON
and OFF frequently without affecting their
lifetime or light emissions being affected.
INSTANT LIGHTING & FREQUENT SWITCHING

15. Benefits of LED lamps over
other luminaires
• Operational life of up to 50,000 hours
• Manageable
• Extremely low maintenance
LONG LIFE
• Resistant to shock, vibrations and external
impacts
• Extremely durable
• Versatile and suitable for most applications
DURABILITY

16. Benefits of LED lamps over
other luminaires
• Last longer than most conventional light bulbs
• There is much less waste in material and
labour
• Free of toxic chemicals such as Mercury
ECOLOGICALLY FRIENDLY
• Produce close to no UV emissions
• Suitable for UV sensitive areas such as art
galleries or museums
• Low radiated heat emissions make them
suitable for goods and materials that are
sensitive to heat.
ZERO UV EMISSIONS

17. Benefits of LED lamps over
other luminaires
• Only a low voltage power supply is required
thereby making it suitable for a variety of
indoor and outdoor applications
LOW VOLTAGE
• Light can be easily directed to a specific
location
• Concentrated beam of light
• Increased efficiency
OPERATIONAL IN EXTREME LOW
TEMPERATURES
LIGHT DISPERSEMENT
• E.g. Freezer rooms