Design and operation of the LED
At the moment, the LEDs just received the widest distribution in many areas of industry. And since the opening in 1963 of the red LED to date technology is constantly evolving. Now on the shelves you can find products made by technology DIP, COB, COG, SMD, filament. In this article I will tell you about each of the technologies and how, by what principle operate all LEDs.
Content
What is an LED
Apparatus DIP type LEDs
SMD-type LED apparatus
LED COB type device
How does the LED
conclusion
What is an LED
So, first let's understand what is a LED. LED - a semiconductor component, in which there is a pn junction, wherein when an electric current flows in the forward direction is generated photon radiation in the visible spectrum.
If we compare with the conventional LED light bulb Ilyich or fluorescent lamp, the main difference will be that the fact that the emission spectrum of the diode is almost completely located in a narrow visible (to the human eye) range. And in order to get a certain color of light is used a special chemical composition of the phosphor directly semiconductors.
Apparatus DIP type LEDs
Let's begin our detailed familiarity with LEDs made by DIP technology.
In most cases, the externally diode implemented as follows: epoxy hemispherical body, inside which a cathode pomeshen triangular platform where the crystal is placed. Adjacent anode connected to the crystal via the thinnest wiring. O performed in various lengths, where the longer leg is a plus, and the shorter - minus.
There are also more complex products with a few crystals, designed for glow in different colors. In addition, the housing may be embedded microchip, used to specify a sequence of operation of the crystals and their frequency of blinking.
Themselves LEDs DIP refer to low-current shell and are mainly used in lighting and display modules. For example, all of our favorite Christmas garlands, just made using DIP LEDs.
It has undergone significant changes, and the LED was created in an attempt to increase the light output of the LEDs in this type of DIP shell with four pins, which received the terrible name of "piranha".
They have been applied in advertising signs, road illumination and etc.
The development of technology has led to the emergence of LEDs produced in SMD technology.
SMD-type LED apparatus
This type of light-emitting diodes (with direct fixation on the surface of the printed circuit board) is very different from its predecessor. appearance LED SMD- It allowed to automate the production of a variety of lighting systems to reduce their size and to reduce the cost.
Today's reality is that right now, this type of LED is the most popular.
Broader and more massive base mounting of the crystal itself has created an excellent heat dissipation during operation of the crystal.
The white LED phosphor such construction takes place between the crystal and the diverging lens. This provides complete elimination of the ultraviolet range and generates two desired color temperature ranges Cool white (Cool white), and warm white (warm white)
LED COB type device
Chip-On-Board This technology is one of the latest developments, which, of course, will soon conquer a niche in the market.
A characteristic feature of this technology lies in the following: on the basis of aluminum (substrate) using a dielectric glue fixed dozens of small crystals without housing and the substrate, more closed matrix formed by a single layer phosphor.
The end result is a light source with uniform light distribution without creating a shadow effect.
kind of COB technology is COG (Chip - On - Glass), crystals where placed on a substrate made of glass. A prime example of this technology is the filament lamp, rated at 220 V.
Where the light source is the glass rods, which are fixed LEDs enclosed phosphor layer.
How does the LED
Despite all the variety of LEDs made by different technologies operating principle they have one and the same, and he concluded as follows:
Conversion of the electron flux in the light flux is carried out in the chip made of different semiconductors. material with n - conductivity obtained by doping with electrons, and the material with p - conductivity - holes. It was formed as adjacent layers, creating additional charge carriers countervailing charges
And it turns out that at the time when the LED forward voltage is applied (on the plus leg served plus, and minus minus) there is a movement of charged particles through the barrier and is triggered electron recombination and a "hole" in the P - N - transition and which releases energy in the form of a photon and a small amount of heat.
In principle, absolutely any semiconductor diode in the course of their work highlights the photons, but in most cases the emission spectrum is outside the visible area to the human eye. Therefore, in order to "force" the LED to emit light in the range of 400 - 700 nm experts had to spend more than one hundred experiments. As a result, where there are such novel compounds as gallium arsenide, gallium phosphide, and other complex shapes.
Since when P-N- transition It stands still and heat in a sufficiently high-power LEDs should be present efficient removal of accumulated heat system.
conclusion
That's all I wanted to tell you about the principle of operation of LEDs and their existing varieties. If the article was useful to you, or are interested in, you will appreciate it Like (This will help to create more materials). And thank you for your attention!