This article will introduce you some basic information of LEDs, you will learn what is LED, what are its characterics, how to and where to use it, how many kinds of LEDs are there, and so on.
What is LED?
A light-emitting diode (LED) is a kind of semiconductor electronic component that can convert electric energy into light energy. The electronic component appeared as early as 1962, emitting only low-light red light at an early stage, and later developed versions of other monochromatic lights, which now has light throughout visible light, infrared and ultraviolet light, and the luminosity has increased to a fairly high degree. With the development of technology, light-emitting diodes have been widely used in display, TV lighting decoration, and lighting sources.
With the rapid progress of LED technology in the 1990s, its luminous efficiency exceeded the incandescent lamp, the intensity of light has reached the candlelight level, but also the color has covered the whole visible spectrum range from red to blue. This technological revolution from LED levels to beyond general-purpose light sources has led to new applications such as automotive signals, traffic lights, large outdoor panchromatic displays, and special lighting sources.
The light-emitting diode is abbreviated as LED. It is made of a compound containing Ga, As, P, N, and so on. The making principle of LED is when the electrons and the holes are combined, the visible light can be radiated. It is one of the semiconductor diodes that can convert electrical energy into light energy.
Compared with ordinary diodes, light-emitting diodes are composed of a PN junction and have unilateral conductivity. When a forward voltage is applied to the light-emitting diodes, the holes injected from the P region to the N region and the electrons injected from the N region to the P region are combined with the electrons and holes in the N region and the P region in the vicinity of the PN junction, respectively, to produce spontaneous emission fluorescence. The energy states of electrons and holes in different semiconductor materials are different. So when their electrons and holes are combined, the energy released is different, and the more energy is released, the shorter the wavelength of light.
Commonly used light-emitting diodes are red, green, or yellow. The reverse breakdown voltage of light-emitting diodes is greater than 5V. Its forward volt-ampere characteristic curve is steep, it must be used in a series current limiting resistor to control the current through the diode. The current limiting resistance R can be calculated using the following formula:
R= (E－UF) / IF
E is the power supply voltage, the UF is the forward voltage drop of the LED, and the IF is the normal operating current of the LED. The core portion of the light-emitting diode is a crystal sheet composed of a P-type semiconductor and an N-type semiconductor, and a transition layer is formed between the P-type semiconductor and the N-type semiconductor, referred to as a PN junction. In the PN junction of some semiconductor materials, if the injected minority carriers are combined with the majority carriers, the rest will be released in the form of light, that is, the electric energy is directly converted into light energy.
When the reverse voltage is applied to the PN junction, and the minority carriers are difficult to inject, so that no light is emitted. When the current flows from the LED anode to the cathode, the semiconductor crystal emits light from ultraviolet to infrared colors, and the intensity of the light depends on the current.
All the content of this article: LED Tutorial
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