Sharp IV-C35M Manual do Utilizador descarregar pdf (Página 14)

C35 Application Note

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RoHS Compliant www.semileds.com

C35 Application Note V1.3

Subject to change without notice

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Page

Thermalmanagement

Figure16.C35LEDL‐Icurve

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Thermalresistance

Figure16showsacross‐sectionandasimplethermalmodelforaC35solderedontheMCPCB.Asimple

thermalmodelorthermalcircuitcanillustratetheheatflowingthroughaMCPCB.Heat

releasepathfrom

locationofheatgenerationforLEDchiptoambientisasbelow:

LEDchipDie‐attachresinceramicMCPCBAmbient

Where:

Tjisthetemperatureatthejunctionofthedevice

TcisthetemperatureattheCeramic

Tbisthetemperatureatthepoint

ofMCPCB

Taistheambientairtemperature

RjcisthethermalresistancefromjunctiontocaseoftheCeramic

RcbisthethermalresistancebetweenthecaseoftheCeramicandtheMCPCB

RbaisthermalresistancebetweenMC PCBandambient

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Unitofthermalresistanceis

o

C/W,

Forexample,10Ԩ/Wmeansthattemperaturegoesup10Ԩpereveryinputpower1W.

Equation1belowrepresentstherelationshipbetweenTjandTa.

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Tj=Ta+Rba×Pd+Rcb×Pd+Rjc×Pd

=Tb+Rcb×Pd+Rjc×Pd

=Tc+Rjc×Pd

Equation1

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Inrealcase,itishardtomeasureTjdirectly,soitwillbeeasiertogettheTjbymeasuringTborTa.Then

theequation1canbesimplifiedtoequation2

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