Temperatur_Measurement_Technique_for_Stabilizing.doc

IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 59, NO. 3, MARCH 2010  661  Temperature Measurement Technique for Stabilizing the Light Output of RGB LED Lamps Xiaohui Qu, Siu-Chung Wong,SeniorMember,IEEE, and Chi K. Tse,Fellow,IEEE  Abstract—The ef?ciency of light-emitting-diode(LED) lights approaches that of ?uorescent lamps.LED light sources ?nd moreApplications than conventional lightbulbs due to their compactness,lower heat dissipation,and real-timecolor-changing capability.Stabilizing the colors of red–green–blue(RGB) LED lights is a challenging task,which includes colorlight intensity control using s witching-mode power converters,color point maintenance against LED junction temperature change,and limiting LED device temperature to prolong the LED life time .In this paper,we present a LED junction temperature measurement technique for apulse width modulation diode for ward current controlled RGB LED lighting system.The technique has been automated and can effectively stabilize the color without the need for using expensive feedback systems that involve light sensors.Perform ancein terms of chromaticity and luminance stability for atemperature compensated RGB LED system will be presented. IndexTerms—Color maintenance,light-emitting-diode(LED) Junction temperature measurement,light-emitting-diode(LED) lighting,red–green–blue(RGB)LED,temperature compensation. I. I NTRODUCTION URRENTLY, ?uorescent lamps represent the most pop- ular lighting solution due to their high luminous ef?cacy and low running cost. However, because of their limited pro- grammability, ?uorescent lamps cannot meet the requirements of many modern applications. Unlike ?uorescent lamps, red– green–blue (RGB) light-emitting diodes (LEDs), with their ca- pability to generate instantly different colors and intensities, are expected to ?nd many applications in areas such as biomedical apparatus [1], detector systems [2], liquid-crystal-display back- lighting [3], [4],