Study on Light Emitting Surface Temperature of LEDs

Infrared (IR) and thermocouple (TC) measurements of the light emission surface of white, blue, red and green LEDs are demonstrated using Transient Thermal Tester (T3Ster). It is shown that the IR measurement could obtain a more accurate result which is lower than the junction temperature (T_j) of LED. However, the TC measurement led to a higher temperature than T_j due to the heating effect resulted from the radiation of LED. IR measurement of the light emitting surface temperature of LEDs with dispensing and remote phosphor driven by the pulsed current is analyzed to show the transient temperature response on light emission surface with correlation between the peak light emitting surface temperature and the pulse current and width.