LED Technology – All You Need To Know

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Which technology really change our life style? You all have different opinions and different answers. But one thing is common for all of us and  that is LED. So in this article”LED Technology- All you need to know” you will have a thorough knowledge about it. 

LED technology really turns around our life style. Starting from Bulbs to phones, monitors and TVs. Because of it, today we are living in a era of smart bulbs which are consuming less power and energy efficient.

So in this article “LED Technology- All you need to know” we will see that How LED works, types of it, advantages of LED and Usage of it.

Simple Hole LED

PARTS OF SIMPLE

HOLE LED

LED Picture

LED TECHNOLOGY- All You Need To Know:

If we say Light Emitting Diode than a lay man could not understand what you are saying. But if you say LED than he will understand perfectly.

So, today in many electronic devices we use these LED technology. For example, today these are generally used in smart-phone displays over and above in the camera flashlights. Similarly, today the LED TVs are quite widespread.

And then if we talk about the lighting, then LEDs are used for the lighting in the houses, in the offices and in streets, roads, runways and stadiums. 

Every where we can see the use of LED bulbs and lighting system. Today from the street lights to the traffic signals, or even for the display boards, the LED technology is  commonly used.

Let’s understand the working of it than we will see different types of LEDs than we will see the advantages of the LED technology. 

How LED Works
WORKING OF LED

WORKING OF THE LED TECHNOLOGY

So, now let’s see the working of the LED. As its name suggests, similar to the PN junction diode, it is also one kind of diode.

But whenever the current flows through it in the forward direction, then it emits the light of the particular color.

So, let’s understand the physics behind it.

In PN junction diode, whenever it is forward biased, then the holes on the P side starts moving towards the N side. And similarly, the electrons on the N side start moving towards the P side.

In this way, both holes and electrons contribute in the flow of current.

And during the movement, these charge carriers used to recombine with each other.

In the PN junction diode, whenever these electrons and holes recombine with each other, then they release the energy in the form of heat.

But in case of the Light Emitting Diode, whenever they recombine with each other, then they release the energy in the form of light.

In the crystal structure, the free electrons have more energy than the electrons which are still in the valance orbit.

And we can say that the free electrons are in the conduction band and the holes or the empty space which is left by the free electrons is still in the valance band.

So, whenever the electrons and the hole recombines, then the electrons from the conduction band comes into the valance band. Or in other words, it comes from the higher energy level to the lower energy level.

And as you know, whenever the electron jumps from the higher to the lower energy level, then it releases the energy in some form. 

In the normal PN junction diode, this energy is released in the form of heat.

Because in the fabrication of this PN junction diode, the different semiconductor materials like silicon and Germanium are used.

And in these materials, during the recombination of the holes and the electrons, the energy is released in the form of heat.

On the other end for the Light Emitting Diodes, during these combination or the transition of the electron, the energy is released in the form of light or the photon.

Because in the fabrication of the Light Emitting Diode, different semiconductor compounds, like GaAs and GaP are used. And in this type of Semiconductor compounds, during the recombination, the energy is released in the form of photons.

WAVELENGTH AND BAND GAP

And the energy of the emitted photon is equal to the band gap. That means the energy difference between this conduction and the valance band. Usually, this band gap is represented in the electron Volt (eV).

So, if Eg =hf= hc/lambda ( h= planks constant and f= frequency of electromagnetic radiation) is the band gap, then the energy of the photon can be given as hc/lambda Where h is the Planck’s constant and the C is the speed of light.

And the lambda represents the wavelength of the emitted light. So, as you can see from the equation, the wavelength is inversely proportional to the band gap. Also it is directly proportional to the frequency of electromagnetic radiation.

By band gap engineering, we can change the color of the emitted light.

Direct semi conductor compounds like GaAs (Galium Arsenide), GaP (Gallium Phosphide), GaAsP (Gallium arsenide Phosphide), Sic (Silicon Carbide), GaInN(Gallium Indium Nitride) which are used to generate the different colors of light.

In below table you can find different LED materials for different colors:

Color

Semi conductor Name

Violate

Indium Gallium Nitride

Infrared

Gallium Arsenide

Blue

Zinc Salenide

Green

Gallium Indium Phosphide

Yellow

Aluminium Gallium Indium Phosphide

Orange

Gallium Arsenide Phosphide

Red

Aluminium Gallium Arsenide

 

 

 

LED DATASHEET
ENERGY BAND DIAGRAM

FORWARD VOLTAGE DROP

If we talk about the electrical characteristic of the Light Emitting Diode, then it is very similar to the PN junction diode.

And if you see the V-I characteristic of the diode, then it will be similar to the rectifier diode.

But for the Light Emitting Diode, the forward voltage drop is larger than the PN Junction Diode.

So, for the PN junction diode, we know that the forward voltage drop is in the range of 0.6 to 0.7V. But for the light emitting diode, depending on the emitted color, the forward voltage drop can vary from 1.8 V to 3.5 V.

As we move from IR towards the blue light, then the forward voltage drop of the diode will increase.

So, for any Light Emitting Diode, in the forward bias condition, when the applied input voltage is more than the forward voltage drop, then the Light Emitting Diode will emit the light of the particular color.

But without any kind of series resistor, the current which is flowing through the Light Emitting Diode will be very high.

And due to that, the Light Emitting Diode may get damaged. So, if you see the datasheet of any LED, then there is always mentioned the maximum forward current of the Light Emitting Diode.

And the current which is flowing through the Light Emitting Diode should always be less than this limit.

So, to restrict the current, the series resistor should always be connected with the Light Emitting Diode.

Out of the different specifications of the Light Emitting Diode which you will find in the datasheets. And we have already talked about the first three specifications.

That is LED current, the forward voltage drop of the LED and the wave length.

So, let’s talk about the last two specifications. Now, the brightness or the Luminous Intensity is usually defined for the LED at the specific current.

BRIGHTNESS OR LUMINOUS INTENSITY AND VIEWING ANGLE:

And this brightness is defined in the unit of millicandela.

So, while selecting the Light Emitting Diode for the specific application, one should also consider this specification.

 

Then the other specification which you often find in the datasheet is the viewing angle. So, basically, it defines the directivity of the Light Emitting Diode.

 

And if you see the datasheet of any LED, then you will find this type of polar radiation pattern for the LED.

So, basically, it defines the angle from the maximum intensity where the intensity drops to the 50 percent.

The intensity is maximum at the center and as we move away from the center then the intensity starts dropping in either direction.

And at this point, the intensity drops to 50 percent. So, for this LED, the viewing angle will be equal to roughly 15 degrees.

If we consider the full angle then it will be equal to 30 degrees.

But in the datasheet usually it, is specified as the half angle.

 

This is all about the different specifications of the LED. Now let’s briefly talk about the different types of LEDs. 

LED Viewing Angle
LED VIEWING ANGLE
Hole LED
HOLE LED
HIGH POWER LED
HIGH POWER LED
SMD & COB LED
SMD AND COB LED

DIFFERENT TYPES OF LED:

HOLE LED

So, the first type of LED is the through hole type of LED. And still, it is very popular among the electronic hobbyist.And still, it is used in the many applications.

SMD LED

Then the second type of LED is the SMD LED. It is also known as the Surface Mount LEDs. This type of LEDs is very tiny in the size and they are mounted or installed on the circuit board itself. And today they are quite commonly used in the LED bulbs and the other applications.

HIGH POWER LED

Then if we talk in terms of power, then there are high power LEDs. So, these LEDs can handle a much more current than the normal LEDs. And therefore they are much brighter than the normal LEDs.But because of the large power dissipation, they are always used with the heat sinks.

COB LED

Then the other type of LED is the COB LED. And it is known as the Chip On Board LED. So, it is very similar to the SMD LED. But here so many tiny LEDs are installed on the same chip. And hence it is much brighter than the other types of LEDs.

 

RGB LED

Then the other type of LED which is commonly used today is the RGB LED. So, if you look at the through hole type of RGB LED then it contains the four leads.

So, if it is a common cathode type of LED, then it has a common cathode and the three anodes for the different colors. That means three anodes for the RED, GREEN and the BLUE LED.

And by changing the current through each LED, we can get the different shades of color. This type of RGB LED is also available in the SMD packages. And these types of LEDs are quite commonly used for the decoration purpose.

 

ALPHANUMERIC LED

At the last let’s talk about the alpha numeric LEDs. So, these type of LEDs are used to display the numbers and the alphabet in the various industries.

 

So, these are the different types of LEDs which are quite commonly used in today’s world. 

THE ADVANTAGES OF THE LED

Now, whenever the LED bulbs are used for the lighting, then they are more energy
efficient than the conventional bulbs.

Also, the lifespan of these LED bulbs is more than conventional bulbs.

Then the third advantage of the LED is that it can be operated in the fast switching
application.

And the other advantages are the smaller size and the better controllability. Now, here controllability is in the sense that the brightness of the LED can be
easily controlled.

 

These are some of the advantages of it. 

USGAE OF LED TECHNOLOGY:

Different usage of LEDs in really:

Ø   Television technology

Ø    SmartphoneTechnology

Ø    LED displays

Ø    AutomotiveLighting

Ø    Flightsand spacecraft lighting

Ø    Road and street lighting

Ø    Decorationand design

Ø Equipment and component parts serviceability lighting

Ø    Computer and server lighting

Ø    Network management lighting

Ø    Different runway and airport lighting

Ø    Dimming light

Ø   Medical equipment lighting

Ø   Li-Fi Technology

 

These are some of the examples of LED usage in modern life style.

 

So this is the end of my article “LED Technology- All you need to know”. Now I think you will have a brief knowledge about it and how it works and where it is being used.

For more such articles keep follow me on facebook, twitter and insta. 

 

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