product. Exceeds this value, the LED heat damage.

 

    (2) Maximum forward DC current IFm: to allow the addition of the forward DC current. Exceeds this value can damage the diodes.

 

    (3) the largest reverse voltage VRm of: allows you to add the maximum reverse voltage. Exceeds this value, the light-emitting

 

    diodes may be breakdown.

 

    (4) work environment topm: light emitting diode a working environmental temperature range. Below or above this temperature

 

    range, the light-emitting diodes will not work properly, the efficiency is greatly reduced.

 

    Two. The significance of the electrical parameters

 

    (1) forward operating current If: it refers to the normal and light-emitting light-emitting diode forward current. In actual

 

    use should be based on the need to select the IF in 0.6 · IFm below.

 

    (2) The operating voltage is given in the forward voltage VF: parameter table in a given forward current. Generally measured at

 

    IF = 20mA. Light-emitting diode forward voltage VF of 1.4 ~~ 3V. VF will drop in outside temperature.

 

    (3) VI characteristics: light emitting diode voltage and current relationship

 

    In the forward voltage is less than a certain value (called the threshold), the current is very small, non-luminous. When the

 

    voltage exceeds a certain value, the forward current with voltage is quickly increased, light. VI curve can be drawn LED's forward

 

    voltage, reverse current and reverse voltage and other parameters. Positive LED reverse leakage current IR <10μA.

 

    LED classification

 

    A. Press the LED light color sub-

 

    LED luminous color points can be divided into red, orange, green (also broken down the yellow-green, the standard green and

 

    pure green), blue. In addition, some light-emitting diodes contain two or three color chips.

 

    According to the light-emitting diode light at the doped or not doped scattering agent, colored or colorless, and the various

 

    colors of light-emitting diodes can be divided into colored transparent, colorless, transparent, colored scattering and colorless

 

    scattering four types. Scattering of light emitting diodes and up to do the lights use.

 

    Two. LED out of the smooth characteristics.

 

    By light-emitting tube out of the smooth characteristics of sub-round light, side lights, rectangular, surface light-emitting

 

    tube, lateral pipe, surface mount using a micro-tube. Circular lamp diameter is divided into φ2mm φ4.4mm, φ5mm, φ8mm, φ10 mm

 

    and φ20mm and so on. Abroad, usually denoted by the light-emitting diode of φ3mm T-1; remember φ5mm the T-1 (3/4); φ4.4mm's

 

    recorded as T-1 (1/4).

 

    The angular distribution of luminous intensity half-value angle size can be estimated round. Figure luminous intensity distribution angle to be divided into three categories:

 

    (1) high directivity. Generally pointed epoxy package, or with a metal reflector cavity package, and does not increase the scattering agent. The half-value angle of 5 ° to 20 ° or smaller, with high directivity, can be used for local lighting, or associated with the optical detection which is part of the automatic detection system.

 

    (2) Standard. Usually used for light, its half-value angle of 20 ° to 45 °.

 

    (3) scattering type. This is the larger perspective of the light, half-value angle of 45 ° ~ 90 ° or greater, the amount of scattering agents.

 

    3. By the structure of the light-emitting diodes

 

    Of light-emitting diode structure, the structure of the full epoxy encapsulation, epoxy encapsulation of the metal base, ceramic base epoxy packaging and glass packaging.

 

    4. Press the luminous intensity and operating current sub-

 

    Luminous intensity and operating current divided into ordinary brightness LED (light emitting intensity <10mcd); ultra-high

 

    brightness LED (light emitting intensity> 100mcd the); luminous intensity in 10 100mcd the Inter-called high-brightness light-emitting diodes.

 

    General the LED current in a dozen mA to tens of mA, low-current LED current below 2mA (brightness of ordinary LED the same).

 

    In addition to the above classification, as well as the chip material classification and functional classification.

 

    Light-emitting diode has a maximum forward current IFm, the maximum reverse voltage VRm limit, when used, should ensure that no more than this value. For safety reasons, the actual current, IF following in 0.6IFm; should be allowed possible the reverse voltage VR <0.6VRm.