RESEARCH ON THE LED THERMAL DEPENDENCE AND EFFECTS IN GONIOPHOTOMETRY MEASUREMENT

摘要

The thermal performance of LED is one of the most important factors for LED measurement. The temperature of high power LED which is represented as junction temperature, ambient temperature and case temperature, will affect the light output in different ways. It has been certified that the junction temperature of LED products is the biggest issue in photometry measurement. The light output sensitivity of LED lamps to ambient temperature is 20 times less than to the heat sink. In goniophotometry measurement, the control quantities related to thermal effects are the air movement and ambient temperature. In order to reduce the variation of light output of tested lamps and luminaires to temperature, especially fluorescent lamp fubes, it is indicated as "air movement in the vicinity of the luminaire should not exceed 0,2 m/s" in CIE 121 for goniophotometry of luminaries. However, does the air movement really affect the uncertainty of goniophotometry measurement for LED lamps and luminaires? In this article, the experiments are carried out for this topic.