The term LED is a general term that is mainly used in the field of light
sources and electronic devices. In general, most people know it as
energy-efficient lighting technology. Although most people are using LED
regularly and are quite familiar with the term, they do not know its full
form. So, what is the full form of LED?
In this article, we have briefly covered the most important topics about LED,
such as the LED full form, what is LED, its construction, types,
characteristics, advantages, disadvantages, and more.
What You Will Learn
What is the full form of LED?
The meaning or full form of LED is ‘Light Emitting Diode’. The use of LED is seen mostly in electronic gadgets. Due to the great
quality of light-emitting technology, LEDs are in widespread use nowadays.
Some of the most common applications of LED can be seen in LED displays, TV
backlighting, smartphone backlighting, LED-based wallpaper or screens, home
lighting, automatic lighting, and more.
The full form of LED can be explained as:
| L | Light |
| E | Emitting |
| D | Diode |
Let's talk about what exactly LED is:
What is LED?
An LED refers to a two-lead semiconductor device that is designed to produce
light when an electric current flows in its course. In particular, it is a
PN-junction diode that typically converts the electric current into a light
source by changing the state of the electrons. This process is called
Electroluminescence.
When there is a voltage supplied to an LED, it produces a non-coherent,
narrow-spectrum light. However, the voltage should only be applied in a
forward bias mode.
Note: The first visible-light was developed in 1962 by Nick Holonyack
(also known as the father of light-emitting diodes). This light was only of
low intensity and restricted to red color, and was developed using gallium
arsenide phosphide. Modern LEDs are available in many colors and produce
extremely high light output.
Types of LED
The following is a list of different types of LEDs that have been developed so
far using semiconductors:
• Miniature LED
• Flash LED
• High-Power LED
• Lighting LED
• Alphanumeric LED
• Red Green Blue LED
Construction of LED
• Like an incandescent light bulb, the LED is also made up of a glass
lens around it that helps distribute light in a limited angular range. Also,
it is sometimes packed in a clear or diffused plastic in place of glass.
• LEDs have semiconductor chips doped with impurities used to form a
PN-junction.
• The semiconductor chips are usually mounted in a reflective tray,
which particularly helps in increasing the intensity of light output.
• The contact is made through the conductive adhesive on the side of
the cathode and by gold wire on the anode side to lead the frame.
• The plastic case is used to surround the chip area of the lead frame.
Circuit Diagram
The circuit symbol of the LED is almost identical to the symbol for the
PN-junction diode. The slight difference between these two symbols is the
arrow symbol in the circuit symbol of the LED. The arrows specifically
indicate that the diode is emitting light. The circuit diagram of the LED
looks like this:
How does a LED work?
Light-emitting diodes are defined as semiconductor light producers. They are
made up of a Type P semiconductor and a Type N semiconductor. In this
composition, P-type semiconductors have high concentrations of holes (positive
charges in general) while N-type semiconductors have high concentrations of
electrons (negative charges).
When the voltage is applied to the PN-junction in the forward biased, the
holes and electrons recombine and consequently generate energy in the form of
photons (or light). The light color of the LED is determined by the energy
bandgap of the semiconductor.
Characteristics of LED
Some essential characteristics of LED are listed below:
• The operating temperature of the LED usually ranges from -31° C to
+60° C.
• Voltage generally varies from 1.5 to 3.5 volts.
• Average power consumption in LEDs is typically 5 watts to 9 watts.
However, it has also been measured around 200 lm / W in lab testing.
• LEDs typically have a starting time of about 100 ms.
• LED only works in forward-biased mode.
• The light produced by the LED is directional.
Advantages of LED
The following are the advantages of LED:
• The power consumption of LEDs is very low, making them
energy-efficient. They can operate at very low voltages.
• The light generated by LEDs is very high intensity and extremely
bright compared to other types of lighting technologies.
• Unlike an incandescent bulb, LEDs do not generate as much heat.
• LEDs have a better life span than other lights. The average lifespan
is approximately five years.
• LEDs have smaller sizes so they can easily fit into smaller areas.
They are flexible and user friendly.
• The light generated by LEDs does not contain an excessive amount of
ultraviolet rays and therefore does not cause harmful effects to our eyes.
• LEDs can reveal true colors of light compared to other lighting
technologies. Therefore, LEDs have a great color rendering index (CRI).
Disadvantages of LED
The following are the disadvantages of LED:
• LED performance mainly depends on the limited temperature of the
operating environment. If they are being operated in a high-temperature
environment, this can lead to the failure of LEDs due to overheating issues.
• The voltage applied across the LEDs must be set above the threshold
and the current must be set below the rating, or it may cause LED loss.
Therefore, there is a need to follow the appropriate voltage sensitivity for
LEDs.
• LEDs require appropriate electrical polarity to light-up and
therefore may require a rectifier to maintain polarity.
• The efficiency of LED lights generally decreases when the supplied
electric current increases.
• LEDs are somewhat more expensive than traditional bulbs, such as
incandescent light bulbs.
• Since LEDs do not produce illumination in a spherical distribution,
they are not suggested to be used in open areas.
• LEDs generate more light pollution than other lighting technologies
to some extent. The reason for this is that cool white LEDs typically emit
proportionately higher amounts of blue light than traditional outdoor light
sources.
Summary
LED (stands for Light Emitting Diode) is a PN-junction diode that produces
light when it passes through an electric current in a forward-biased mode.
Nowadays, LEDs are in widespread use because they are more energy-efficient,
durable, and brighter. They are believed to save about 80% of energy compared
to other light sources.
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