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What is LED Lamp? – Construction, Working, Advantages & Applications
LED Lamp
An optoelectronic device which emits light based on the principle of electroluminescence is known as LED (Light Emitting Diode) lamp.
Electroluminescence is the emission of light due to the interaction of an electric field with a suitable solid. It was noticed in 1962 that a forward biased gallium-arsenide junction was found to be an efficient emitter of radiation.
In case of electroluminescent p-n junctions, when biased in the forward direction, some of the energy dissipated is converted into light and hence, these are also called as semi-conductor lamps.
Construction of LED Lamp
For the construction of LED lamps, following semiconductor materials are used −
Gallium Phosphide (Green / Red)
Gallium Arsenide Phosphide (Yellow / Red)
Gallium Nitride (White)
In order to construct an LED lamp, a layer of P-type semiconductor material is placed above the N-type semiconductor layer. A metal film is used on the P-type layer to provide anode connection to the device. Similarly, a gold-film is formed on the N-type layer to provide cathode connection. The gold-film also provides reflection of light from the bottom surface of the device. This increases the efficiency of the LED lamp. The above figure shows the basic construction of an LED lamp.
Working of LED Lamp
When a DC power supply is applied to an LED lamp in forward bias, the majority charge carriers start drifting, i.e., electrons towards the positive terminal and holes towards the negative terminal of the source. At the PN junction, the recombination of electrons and holes takes place, due to the recombination of these charge carriers, the energy is released either in the form of heat or light.
The semiconductor materials such as gallium phosphide (GaP), gallium Arsenide Phosphide (GaAsP), gallium nitride (GaN), etc. emit light on the recombination of electrons and holes at the PN junction. The electrons in these semiconductor materials lose their energy by the emission of light photons. If the semiconductor material is translucent, the emitted light at the PN junction will be transferred outside. In this way, an LED lamp emits light.
Advantages of LED Lamps
The advantages of using LED lamps are as follows −
The operating cost is very less.
They are compact in size.
LED lamps provide easy control of light.
Remote switching and control can be implemented in the LED lamps.
LED lamps have longer life, up to 100000 hours.
LED lamps are energy efficient and low current consuming.
These lamps are mechanically robust.
LED lamps provide excellent color rendering.
These lamps are environment friendly, as not having any toxic content.
Disadvantages of LED Lamps
Listed below are some of the disadvantages of using LED lamps −
The initial cost of the LED lamps is very high.
As LED lamps are semiconductor devices. Thus, they are temperature sensitive and temperature dependent.
LED lamps require DC supply, therefore, rectification unit is required in the lamp circuit.
The high intensity light produced by an LED lamp has impact on the insects.
Applications of LED Lamps
LED lamps are used in the following applications −
For domestic and commercial lightings.
Used as indicating lamps.
Used as bi-color indicators.
LED lamps are also used as fault indicators in control panels.
In display boards.
Used for decorative lighting.
In mobile phone and wrist watches screens.
Used as head lamps in automobiles.
LED lamps are also used in various instruments in different industries.
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