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ThermaldResistancedofdMultipledLightingdLED
ThedoveralldthermaldresistancedofdmultipledLightingdLEDddescribingdyourdspecifcdapplicationdneedsdcandbeddeter-
mineddbydusingdparalleldthermaldresistancedmodeldasdshowndindFigured2

TJunction

R TH, J-C

TCase

R TH, C-B

TBoard

R TH, B-A
ddd
TAmbient

Figure 2. Thermal Resistance Model of Multiple Lighting LED

BydusingdthedparalleldresistancedequationdwedcandobtaindRTH,dJ-Bdofdabovedarray:
1 1 1 1
+ .....
Overall RTH, = LED1 RTH, + LED2 RTH, + LEDn RTH, ............................................................................... ( 4 )
J-B J-B J-B J-B
Assumingdalldthedparalleldresistancesdaredofdthedsame,dEquationd4.dthendbecomes:

1 n
Overall RTH, = LEDx RTH, .................................................................................................................................. ( 5 )
J-B J-B
dddor
Overall RTH, = LEDx RTH, .................................................................................................................................. ( 6 )
J-B J-B
n
Where
nd=dTotaldnumberdofdLightingdLEDdindabovedsystem

IndthisdcasedthedTJunctiondofdadmultidLightingdLEDdsystemdcandbeddescribeddasdfollowd:

Td d=dTd d+d(dP d)dxd(dOveralld_dR d)d...................................................................................................d(d7d)
Junction Ambient d_Total TH,dJ-A
Where

P d_Total d=dTotaldpowerd(dWd)ddissipateddfromdemitterdsystem
Overalld_dR =dOveralld_dR d+dR d...........................................................................................................d(d8d)dd
TH,dJ-Ad TH,dJ-B TH,dB-A
ItdisdstronglydrecommendeddthatdthedmaximumdTdBoarddofdLightingdLEDdbedconsidereddunderd90d@Cdevendfordshortddddd
durationsdwhileddesigningdthedthermaldmodeldfordyourdspecifcdapplications.

Lighting LED > Application Notes

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