Key Features and Benefits of Various LED Types
LEDs are also known as light emitting diodes, it's a semiconductor light emitting source that emits light when current is flown through it. Semiconductor electrons recombine with the electron holes releasing energy in the form of photons. Corresponding to the energy of photons the colour of light is determined, and also by the energy required by photons to cross the semiconductors band gap. By using multiple semiconductors, white light is obtained or by a layer of light emitting phosphor on the semiconductor device.
The particle electronics components appeared in 1962. The earliest LED emitted low intensity infrared light in remote controlled circuits such as those used with a wide variety of consumer electronics.
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History of LED
A phenomenon known as electroluminescence was discovered in 1907, by the british experementor named H.J Round of marconi labs by using a crystal of silicon carbide and cat's-whisker detector.
Oleg Losev, a Russian inventor, reported creation of the first LED in 1927. His research was distributed in Soviet, Germany, British scientific journals but no practical use was made of these discoveries for several decades.
Georges Destriau, in 1936 observed that electroluminescence could be produced with zinc sulphide power is suspended in an illustrator and an alternating electrical field is applied to it. In his distrial publication he often referred to luminescence as losev-lights.
He worked in the lab of madame Marie Curie, also an earlier pioneer in the field of luminance with research of radium.
Hungarian Zoltan Bay along with Gyorgy Szigeti, in Hungary pre attempted LED lightings in the year 1939 by pertaining a lightning device with an option on boron carbide, that emitted yellowish white, white or greenish white light depending on the impurities present.
Carl Accardo, Edward Jamgochain and Kurt Lehovec, explained these first LEDs in 1951 using an apparatus employing SiC crystals with a current source of a battery or a plus generator.
Types of LED
LEDs are made up of different packages and are used for different purposes.
Miniature:
These are mostly single die LEDs and they are available in various shapes and sizes from 2mm to 8mm through holes and the surface mount package. And the current rating ranges lie between 1mA to above 20mA. The multiple LED dies get attached to a flexible backing tape from an LED strip light.
AC Driven:
These are the LEDs developed by the seoul semiconductor. It can be operated on AC power without a DC convertor. For each light cycle the LEDs part emits light which is dark. And this is reversed during the next half cycle.
High Power:
These high outputs or high power LEDs can be driven at currents from 100 of mA to more than an ampere. Some can emmite over thousands of lumen.
Overheating is proved to be destructive for the LEDs so the HP-LED can often replace an bulbe in a flashlight. It can be set in an array to form a powerful LED lamp.
Advantages and Disadvantages of LED
LEDs are used in many places here are some of the advantages of an LED:
More lumens are emitted by LED per watt as compared to incandescent light bulbs. The LED lightning efficiency fixture is not affected by the size or shape, unlike fluorescent light bulbs or tubes.
Colour LEDs can emit light of different colours without using any colour filter as the traditional lightning method needs. It can lower efficient costs, this is more efficient.
Their size is adjustable from big to big and small to small. And are easily attached to the printed circuit board.
LED lights up quickly, a red indicator light achieves full brightness light under a microsecond. At times the LED gives a faster response.
Disadvantages:
The LEDs performance largely depends on the ambient temperature of the thermal management properties or the operating environment also.
LEDs must be supplied with a voltage which is above their threshold voltage, and current below their rating.
Area light source: the single LEDs do not approximate a point source of light which is giving a spherical light distribution.
Uses of LED
Uses of LEDs fall majorly under four categories that are:
In the visual signals where the light goes more or less directly from the source inside the human eyes, it does so to convey a message or meaning.
In illumination: where light is reflected from the objects to give visual responses. Interacting and measuring with the processes involving no human vision.
It’s also used in the narrow light sensor where LEDs operate in a reverse biased mode. And they respond to the incident light also instead of emitting light.
Due to their small size they can easily be fitted in anywhere and can be used time and again they are also available in many different shapes and sizes according to the users requirements.
FAQs on Types of LED Explained in Physics
1. What is the fundamental principle behind a Light Emitting Diode (LED)?
An LED, or Light Emitting Diode, is a p-n junction diode that operates under forward bias. When a sufficient voltage is applied, electrons from the n-side cross the junction and recombine with holes on the p-side. This recombination process releases energy in the form of photons, which we see as light. The colour of the emitted light depends on the energy band gap of the semiconductor material used.
2. How are the various types of LEDs typically classified?
LEDs can be classified based on several criteria, providing different ways to categorise them. The most common classifications include:
- By Model Type: Such as Through-Hole LEDs (the classic bulb shape with long leads) and Surface Mount Device (SMD) LEDs (compact chips soldered directly onto circuit boards).
- By Light Output: Including low-current, standard, and high-power LEDs, which determine their brightness and application.
- By Colour: Single-colour, bi-colour, tri-colour, and RGB (Red, Green, Blue) LEDs.
- By Special Technology: This includes Organic LEDs (OLEDs) and Quantum-dot LEDs (QLEDs).
3. Why do different LEDs emit different colours like red, green, or blue?
The colour of light an LED emits is determined by the semiconductor material used to make the p-n junction. The energy released during electron-hole recombination corresponds to a specific wavelength (and thus colour) of light. This energy is dictated by the material's forbidden energy gap. For instance:
- Gallium Arsenide (GaAs) is often used for infrared LEDs.
- Gallium Arsenide Phosphide (GaAsP) can produce red to yellow light.
- Gallium Nitride (GaN) is crucial for producing blue and green LEDs.
By using different materials or alloys, manufacturers can precisely control the output colour.
4. What are the key differences between Through-Hole and SMD LEDs?
Through-Hole and Surface Mount Device (SMD) LEDs are two primary physical forms. Through-hole LEDs are the traditional type with long metal legs (leads) that pass through holes in a circuit board and are soldered on the other side. They are durable but bulky. In contrast, SMD LEDs are compact, chip-like components that are soldered directly onto the surface of a circuit board. This makes them much smaller, more efficient for automated manufacturing, and allows for a higher density of lights, which is why they are common in LED strips and screen backlights.
5. What are some real-world applications for different types of LEDs?
Different types of LEDs are chosen for specific uses based on their brightness, size, and colour. Key applications include:
- Miniature LEDs: Used as indicators on electronic devices like mobile phones, routers, and remote controls.
- High-Power LEDs: Essential for applications requiring intense brightness, such as automotive headlights, streetlights, and household light bulbs.
- RGB LEDs: Used in decorative lighting, television screens, and smart lighting systems where colour can be changed dynamically.
- Infrared (IR) LEDs: Commonly found in remote controls for TVs and other appliances to transmit signals.
6. How does an Organic LED (OLED) work, and how is it different from a standard LED?
An Organic Light Emitting Diode (OLED) functions similarly to a standard LED but uses organic (carbon-based) compounds for its emissive layer instead of inorganic semiconductor crystals. When voltage is applied, the organic layers emit light directly. The key difference is that OLEDs can be made into thin, flexible sheets, allowing them to be used for advanced displays in TVs and smartphones that do not require a backlight. This results in deeper blacks, higher contrast, and more power efficiency compared to conventional LED-backlit LCD screens.
7. Are all 'white' LEDs created using the same technology?
No, there are primarily two different technologies used to create white light from LEDs. The most common method is the phosphor-based system, where a blue LED is coated with a yellow phosphor. The blue light from the diode excites the phosphor, causing it to glow yellow. The combination of blue and yellow light appears as white to the human eye. The second method is the RGB system, which combines the light from separate red, green, and blue LEDs in close proximity. By controlling the intensity of each colour, a wide spectrum, including white, can be produced.
8. What is the standard circuit symbol used to represent an LED?
The circuit symbol for an LED is very similar to that of a standard diode, but with an addition to signify its light-emitting property. It consists of a triangle pointing towards a bar (representing the anode and cathode, respectively), with two small arrows pointing away from the symbol. These arrows indicate that the diode emits light when forward-biased and current flows through it.
