To study how the attenuation of white LED happens and develops

four types of white LED are studied in this paper. Three of them are PLCC-4 type white LED and the other is power white LED. And the PLCC-4 type white LEDs are encapsulated by YAG phosphors

phosphors wafer or RGB LED respectively. The power white LED is encapsulated by YAG phosphors. Four types white LED are lighted continuously and the same type LED is lighted under the same conditions

such as electrical current

environment temperature

and so on. The emission spectra of them are studied in a interval. Usually

the interval is one week time. In this paper

the attenuation of red

green and blue emission is analysed by studying the emission spectrum change

through which to deduce the attenuation of white LED. Four types of white LED were studied and the results indicate that the attenuation mostly results from attenuation of blue LEDs and quenching of phosphors. The attenuating course of PLCC-4 type of white LED encapsulated by phosphors wafer and RGB LED is the same with that encapsulated by YAG phosphors

which is results from the blue LED only. The attenuating course of power white LED is different from PLCC-4 type white LED. Not only attenuation of blue LEDs is the cause of attenuation of power white LED

no less than 80 percent

but quenching of phosphors is also the other factor. More conclusion could be deduced from the study that if radiator is enough perfectly

the attenuation of white LED results from the attenuation of blue LED

but as the system temperature raises

the quenching of phosphors would happen and which will enhance the attenuation of white LED. In this paper

the attenuation of red

green and blue emission are studied by tracking and analysing their spectrum change to deduce the attenuation mechanism of white LED

and the results will provide a reference to the application of white LED and for the further study.