The principle of LED

- Sep 15, 2018 -

It is a kind of semiconductor diode, which can convert electric energy into light energy. LEDs, like ordinary diodes, consist of a PN junction and have unidirectional conductivity. When the light emitting diode is coupled with a forward voltage, the hole injected from the P zone into the N region and the electrons injected into the P region by the N region, respectively, in the vicinity of the PN junction with the N region of the electron and p region of the hole compound, generating spontaneous emission of fluorescence. The energy state of electrons and holes in different semiconductor materials is different. When electrons and holes are combined, the amount of energy released is different, and the more energy is released, the shorter the wavelength of light emitted. Commonly used is a red, green or yellow light diode. The reverse breakdown voltage of the light emitting diode is greater than 5 volts. Its forward volt-ampere characteristic curve is very steep, and it must be used in series with a current limiting resistor to control currents passing through the diode.

Current-limiting resistor R can be calculated as follows:

R= (E-UF)/if Type E is the supply voltage, UF is the forward voltage drop of the LED, if is the normal operating current of the LED. The core of the light emitting diode is a wafer consisting of a P-type semiconductor and an n-type semiconductor, a transition layer between the P-type semiconductor and the N-type semiconductor, called the PN Junction. In the PN junction of some semiconductor materials, the injected minority carrier and the majority carrier compound will release the excess energy in the form of light, thus converting the electric energy directly into the energy. PN Junction Plus reverse voltage, a few carriers difficult to inject, it does not emit light. The diode called Light Emitting diode, which uses the injected electroluminescence principle, is commonly known as LEDs.

When it is in the positive working state (that is, with positive voltage at both ends), when the current flows from the LED anode to the cathode, the semiconductor crystals emit light from ultraviolet to infrared color, and the intensity of the light is related to the current.