What are LEDs?

LED is an acronym for “Light Emitting Diode”. LED is a semiconductor device that produces light. Initially, LEDs were only used for signaling (notifying electronic devices on and off, whether there is electricity or not, …) but now they are widely used for many large and small lighting applications. different as indoor, outdoor and decorative lighting. Here are some pictures of LED:

The image above shows 4 LED encapsulation technologies used for a variety of applications. The first image may be very familiar to you, if you want to learn more about them check out this article: Differences between LED technologies: DIP vs SMD vs COB vs MCOB

Electronic symbol for LED

The symbol represents the diode with the cathode, the anode and two arrows representing the glow.

Viewing: what is led

LEDs have a long history dating back to 1907 when a British physicist discovered silicon carbide crystals that could produce light when passed by an electric current. Rubin Braunstein of the Radio Corporation of America along with Robert Biard and Gary Pittman of Texas Instruments contributed to the development of infrared LEDs. In 1962, a GE scientist, Nick Holonyak developed the first visible light LED. This LED emits red light. Then George Craford developed the yellow light LED. And in the early 1990s, Shuji Nakamura of Nichia company invented the LED with blue light, paving the way for the hybridization of white light LED in the late 1990s.

See details: The development history of LED lights

How does an LED work

? Similar to a diode, an LED is composed of a cathode and an anode separated by a semiconductor block at the center. This semiconductor block is coupled by two types of P and N. The whole is placed in a plastic shell, which acts as a prism to direct the emitted light.

Structure diagram of LED (Image copyrighthttp://commons.wikimedia.org/wiki/File:LED_Device.jpg)

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When current flows from the pole (P side) to the cathode (N side). At the border of the two sides of the P-N junction, some electrons are attracted to the hole and when they approach each other, they tend to combine to form neutral atoms. This process can release energy in the form of light (or electromagnetic radiation of nearby wavelengths).

The figure above shows the spectrum of electromagnetic radiation. Of the various components of visible light red has the longest wavelength of 700 nm (the least energetic) while violet has the shortest wavelength of 400 nm (the most energetic).

Since an LED produces light in a narrow range of wavelengths, phosphors are often used to improve the spectrum of white light produced by an LED. It is also possible to combine multiple LEDs with different wavelengths to produce full spectrum light.

Construction of LEDs

Below is the structure of a most common LED product, Bulb.

Not only true for Bulb lamps, other types of LED lamps also often have similar components in the structure of the luminaire. We will go from the parts above:

Prism – LED light is directional light. The standard light distribution angle of LEDs is 180 degrees and the light output is about the top half of the bulb. For some LEDs, the distribution angle is adjustable, with different narrow and wide beams. Illumination angle can be changed by prism. Polycarbonate prisms are preferred because they block light and are relatively easy to manufacture. The surface quality and shape of the prism are very important to ensure the propagation of light and to limit the loss in light output. LED Chip – As we learned above, this is the part. emitting light for the lamp.Substrate material– Usually a PCB metal core used to mount LEDs. Besides providing a surface to mount the LED chip, the metal core also helps to transfer it to the heatsink with a larger contact surface.

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Interface materials – Usually glue or grease. This part is used to maximize contact when attaching the surface layer to the heatsink to maximize heat transfer. Radiator – Heatsink comes in two types. Active heatsink, usually a fan used to circulate air. Passive heatsinks use metal fins to dissipate heat. Active heatsinks are usually better at dissipating heat, but in most applications a copper heatsink is sufficient to keep the luminaire at its best operating temperature.

Temperature is the most important factor affecting lamp life, so they deserve a lot of attention. If you want to know more about the lifespan of LEDs, you can check out this article: Factors affecting LED life

Advantages of LED technology

LED lights have a lot of different advantages/benefits that can be mentioned. Following are some of the main advantages of LED technology.

Light output – In 2002, light output from LEDs was at 20 lm/W. Lamp Today commercial LED luminaires have an efficiency of up to 150 lm/W. And according to reports the test bulbs gave out light output of up to 208 lm/W. The efficiency achieved has far exceeded the light produced by incandescent bulbs (15 lumens/watt) or fluorescent lamps (80-95 lumens per watt). With higher efficiency, which means lower power consumption, the payback when using LED lights compared to the above traditional bulbs is only about 1 year depending on the usage time. use.

Lifespan – LEDs have a lifespan of 30,000 to 100,000 hours. Most commercial LEDs have a lifespan of 30,000 to 50,000 hours. This means that when using LEDs, you can use them for 10 to 30 years, depending on the number of hours of operation per day. The long life reduces maintenance costs and makes these bulbs especially suitable for hard-to-reach locations, such as factory lights or street lights, where there are significant maintenance costs.

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Operating characteristics – LEDs operate at lower temperatures, are insensitive to low temperatures and are unaffected by frequent shutdowns. This makes them safer, more efficient in cold environments (outdoor lights, refrigerator lights and cold storage lights) and better for applications that require frequent switching on and off lights. These bulbs are not affected by vibration making them the best choice for places like bridges.

Shockproof – The active components of the LED are isolated from the outer surface with a high-quality insulating layer. The electrodes and the LED package and the electronic components are all housed in a safety enclosure. A layer of material between the LED and the heatsink ensures that no current can leak into the heatsink.

Anti-vibration – If you look at the picture of the LED at the top, you will notice that the electrodes are encased in clear acrylic. There is no filament in the bulb, so LEDs are resistant to vibrations. Many people who use cars, motorcycles and travel devices have switched to using LED lights because of this advantage.

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Types of LED lights on the market

There are many types of LED lights available on the market: Miniature LED lights, AS-LEDs, LED string lights, downlights, factory high bay lights, LED flood lights, LED street lights, … about this riclix.com has Separate article, please read the article: Types of LED lights on the market


These are the basic information to answer the question What is LED? Any comments or other questions, please contact us via the contact form on the website.