Light-emitting diode

Semiconductor light-emitting devices include light-emitting diode (LED), digital tube, symbolic tube, meter tube and dot matrix display (matrix tube) and so on. In fact, each light-emitting unit in a digital tube, a symbolic tube, a meter-shaped tube, and a matrix tube is a light-emitting diode.

1.Working principle

LEDs are made of I-IV compounds, such as GaAs ( GaAs ), GaP ( GaP ), and GaAsP ( GaAsP ) and other semiconductors , the core of which is the PN junction. Therefore, it has the characteristics of forward conduction, reverse cut-off and breakdown of the general PN junction. In addition, under certain conditions, it also has luminescence characteristics.

Under the action of forward voltage, the electrons are injected into the P region from the N region, and the holes are injected into the N region from the P region. The minority carrier ( minority carrier ) part enters into the other region and emits light with the majority carrier ( multison ) recombination. Now there are infrared, red, yellow, green and blue light emitting diodes.

2. Key characteristic

(1) Limit parameter :

1)Permissible power consumption Pm : maximum value of the product of the forward DC voltage across the LED and the current flowing through it. If this value is exceeded, the LEDs are hot and damaged.

2)Maximum forward DC current Im : maximum forward DC current that is allowed on LEDs. If this value is exceeded, the diode can be damaged.

3)Maximum reverse voltage URM : the maximum reverse voltage allowed on both ends of the LEDs. If this value is exceeded, the LEDs may be damaged by breakdown.

4)Working environment topm : the ambient temperature range that the LED can work normally is called the working environment. Under or above this temperature range, the LED will not work, and the efficiency will be greatly reduced.

 (2) Electrical parameters :

1) Peak wavelength :

The light emitted by a certain LED is not a single wavelength,  the light intensity is the largest, and the wavelength is the peak wavelength.

2)Luminous intensity : usually refers to the normal ( on the cylindrical light-emitting diode is the axis ) direction of the luminous intensity.

As the light intensity of the general light emitting diodes is small, the luminous intensity is commonly used by candela ( cd ) as a unit.

3) Spectral Half Width : it represents the spectral purity of the light-emitting tube.

4)The half value angle and the angle of view: the half value angle is the angle between the direction of 1/2 and the luminescent axis, while the angle of the half value angle is 2 times the angle of view (or half power angle).

5) The forward operating current Ip: It refers to the forward current value of a light-emitting diode when it normally emits light.

6)Forward operating voltage Up: The operating voltage given in the parameter table is generally measured at Ip = 20mA. The light emitting diode is forward to the working voltage of Up in 1.4 ~ 3V. When the external temperature rises, the forward working voltage will decrease.

If you want to know more, our website has product specifications for LEDs, you can go to Allicdata Electronics Limited to get more information.