What is Luminous efficiency of LED light fixtures?
Efficient indicators of the evaluation of the light source, the light emitted luminous flux (lm), and the ratio of the power input to the light source (W). Units of lm / W.
Luminous efficiency is only said that the efficiency of the light source, with the light source mounted to the overall efficiency of the lighting appliances APPARATUS (overall efficiency) is a different concept.
The luminous efficiency is to indicate the value of the external quantum efficiency with visual sensitivity (the sensitivity of the human eye to light). The external quantum efficiency is the proportion of the number of photons emitted to the outside of the LED chip and the package with respect to the electronic number (current) flowing through the LED. External quantum efficiency can be used in combination of the white LED of the blue LED chip and the phosphor, with respect to the internal quantum efficiency (the number of photons in the light-emitting layer of the LED chip to total electron number of the proportion of the (current) flowing through the LED chip) , the light extraction efficiency of the chip (the emitted light were taken out to the outside of the LED chips of the proportion), the conversion efficiency of the phosphor (the chip emits light to the proportion of the phosphor is converted to a different wavelength) and packaging of the light-extraction efficiency (emitted by the LED and a phosphor, to the proportion of light in the outside of the package) of the product decision.
Within the part of the photons generated in the light emitting layer or in the LED chip is absorbed, or reflected in the LED chip, and not out of the LED chip. Therefore, the external quantum efficiency is lower than the internal quantum efficiency. The luminous efficiency of 100lm / W white LED, the input power is only 32% of the light output to external. The remaining 68% is converted into heat.