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How easy way to speculate led junction temperature number?
2013-09-04 23:02:55
How easy way to speculate led junction temperature number?
A plurality of LED in series, using constant current power supply, the use of volt-ampere characteristics presumed effect of temperature rise in junction temperature in degrees
In many applications (such as fluorescent lamps), tend to be a lot of LED series, this time, LED temperature coefficient effect is even more apparent. Because the use of constant current power supply when the effect is equivalent to volt-ampere characteristics of each LED superimposed along the voltage axis.
If the temperature is 60 degrees, then the volt-ampere characteristic will be shifted to the left 0.12V, if 10 LED series, all the volt-ampere characteristics all left, total offset will reach 1.2V. This is a very impressive figure.
In turn, can also use this feature to the LED junction temperature measured, for example, a 10 Series 3 and the LED combination, the constant current source connected to the future, measured obtaining lower forward voltage drop from 32.3V to 30.6V. Change of 1.7V. It can be speculated that its junction temperature rises to 85 degrees 1.7/10/.002 =85