Study LED decay

LED decay

1.LED decay

LED decay refers to LED after a period of light, the light intensity will lower than the initial intensity, and can not be restored, lower part called LED decay. At present, China has not yet developed the definition and standard of LED decay. GB/T24823-2009 LED module performance requirement is light in luminous maintenance rate 3000h, the luminous maintenance rate should not be less than a product only 92% trial indoor lamps, the industry generally called for countries to develop LED decay standards as soon as possible.

2.LED light source component is damaged more than the temperature limit is irreversible

As everyone knows, LED after its intensity with the chip junction temperature decreased, photosynthetic efficiency decreased, which is the inherent physical properties of semiconductor with temperature changes, as long as the light source of a component does not exceed the temperature limit and.LED damage after stopping the temperature drop to the original value, the intensity of light will recover, that is to say LED no matter how long, repeated several times as long as the initial intensity invariant cannot think light, light is light for a long time working temperature exceeds the limit value of light intensity to restore to the initial value which is called the decay of flux decline is the real meaning of life is irreversible. LED light source component is damaged more than the temperature limit is irreversible.

3 at present, all the chip factory and packaging factory nominal light efficiency are transient light effect

Some people think that the curve of American CREE company announced the LED chip junction temperature is between LEF decay curve, many people regard it as the LED chip and the decay curves, packaging factory will also search it copied to factory specifications, this is wrong.

Figure CREE publicity temperature and flux / curve of optical power is expressed in the design to the user use not allowing the chip junction temperature range based on more than a certain, in order to ensure the rated optical power leads to flux decline or decay. The author thinks that the causal relationship between these curves are not LED chip attenuation, it should be LED light flux and temperature on the various elements of the integrated curve. Many people think that this group is single chip attenuation curve, not including fluorescent powder, viscose, stents and temperature related system components, this is a misunderstanding. The LED light source, whether it is Ta=25 or at Ta=85 DEG C, is a steady state measurement of the light source system at a given temperature

The steady state temperature, light efficiency and many variables influence, complex test is not accurate enough, but longer, so the light efficiency of all the chips factory and packaging factory foreign nominal is transient light effect, so the downstream user acceptance. No matter which company in the world announced product performance indicators must be operational and repeatable, that is to say, the customer to buy your product to its specifications can not or difficult to test, it can not pass. Some foreign manufacturers to boast large efficiency than the traditional value several times is of no practical significance, because the LED light efficiency and light attenuation is not caused by LED single chip, it is related with the system resistance of many conditions, take the test room light effect that only propaganda no practical significance, such as a company to launch 303LM/W products and closed to the market, the industry can not understand and agree. It decides the luminous efficiency of LED chip is not the only reason, is not the main reason, users blindly pursue a brand and not pay attention to the design of the system is misunderstanding, will double, toil with no gain.