LED flood light 50won August 18th, 2012 at 7:01 AM
The brightness of the high power LED light is another important performance parameters, has a strong directional. The brightness of the Dhamma line direction BO = IO / A, specify a direction on the surface brightness of the luminous body is light-emitting unit projected area of the surfaces of the luminous flux emitted in unit solid angle, in units of cd/m2 or Nit.
If the light source surface is an ideal diffuse surface brightness of BO and independent of the direction is constant. Clear blue sky and the surface brightness of the fluorescent the approximately 7000Nit (nits) from the ground to see the brightness of the sun’s surface is about 14 × 108Nit.
LED 120w brightness is related to the applied current density, the general LED, JO (current density) increase in the BO (brightness) is also approximate increase. In addition, the brightness and the ambient temperature, ambient temperature, ηc (composite efficiency) decreased, BO decreases. When the ambient temperature is constant, the current increases enough to cause the pn junction temperature rise, temperature rise, brightness was saturated.
Aging: attenuation of light intensity or brightness of the high power LED 1w brightness with long working hours. Degree of device aging is related to the size plus a constant current source can be described as Bt = BOe-t / τ, Bt brightness after time t, BO for the initial brightness.
Usually the brightness down to Bt = 1/2BO experienced at time t is called the life of the diode. Determination of t take a long time, usually obtained in the projected life expectancy. Measurement method: LED 3w through a certain constant current source, the light from 103 to 104 hours, has measured BO Bt = 1000 ~~ 10000, substitution of Bt = BOe-t / τ calculated τ is; then Bt = 1/2BO into the , life can be obtained t.
A long time and believe that LED 10w life expectancy of 106 hours, which refers to a single LED in the IF = 20mA under. With the power LED development and application of foreign scholars believe that the basis of the percentage value as a life LED light attenuation. If the LED light attenuation for the original 35%, life expectancy> 6000h.
The optical parameters of the LED junction temperature of the pn junction has a great relationship. Generally work long hours in the small current IF <10mA or 10 ~ 20mA lit LED temperature rise is not obvious. If the ambient temperature is high, the dominant wavelength of the LED or λp will drift to the long-wavelength, BO will fall, especially the temperature rise of dot-matrix display, LED flood light 50w reliability and stability of specially designed scattering ventilation device .
The dominant wavelength of the LED temperature relationship can be expressed as λp (T ‘) = λ0 (T0) + △ Tg × 0.1nm / ℃
By the above equation, whenever the junction temperature rise 10 ℃, the wavelength drift to the long-wave 1nm, and the luminous uniformity, consistency variation. This small, densely packed in order to improve the intensity per unit area, the brightness of the design in particular, should pay attention to heat a good shell lamps or specialized general equipment to ensure long-term LED as the lighting of the lamps light requirements