Datasheet

0
5
10
15
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25
30
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40
45
50
0 10 20 30 40 50 60 70 80 90 100
Power Disspated, P
d
(Watts)
Natural Co nvection
20 ft. /min. (0.1 m/s)
100 f t./min. (0 .5 m/s)
200 f t./min. (1 .0 m/s)
300 f t./min. (1 .5 m/s)
400 f t./min. (2 .0 m/s)
500 f t./min. (2 .5 m/s)
600 f t./min. (3 .0 m/s)
700 f t./min. (3 .5 m/s)
800 f t./min. (4 .0 m/s)
ThermalCurve
TheoperatingcasetemperaturerangeofMHB-75seriesis-40 Cto+100 C.WhenoperatetheMHB-75series,properde-ratingor
o o
coolingisneeded.
Themaximumcasetemperatureunderanyoperatingconditionshouldnotbeexceed100 C. Thefollowingcurveisthede-rating
curveofMHB-75serieswithoutheatsink.
o
Power Dissipated vs Ambient Temperature and Air Flowwithoutheatsink
Ambient Temperature, Ta
( )
Air Flow Rate Air Flow RateTypical Rca Typical Rca
Rca: Thermalresistancefromcaseto
ambience
Naturalconvection
20ft./min.(0.1m/s)
7.12 / W
100 ft./min. (0.5m/s)
500 ft./min. (2.5m/s)
6.21 / W
2.96 / W
200 ft./min. (1.0m/s)
600 ft./min. (3.0m/s)
5.17 / W
2.53 / W
300 ft./min. (1.5m/s)
700 ft./min. (3.5m/s)
4.29 / W
2.37 / W
400 ft./min. (2.0m/s)
800 ft./min. (4.0m/s)
3.64 / W
2.19 / W
75WDC-DCHalf-BrickRegulatedSingleOutputConverter
MHB75 s er ie s
FileName:MHB75-SPEC2011-09-08
Example:
WhatistheminimumairflownecessaryforaMHB75-48S12operatesatnominalline,anoutputcurrentof6.25A,andamaximumambient
temperatureof40 ?
Solution:
Given:Vin=48Vdc,Vo=12Vdc,Io=6.25A, (unitefficiency)=89%
DeterminePowerdissipation(P ):
P =12 6.25 (1-0.89)/0.89=9.27Watts
Determineairflow:
Given:P =9.27Wand Ta=40
Check ThermalCurveabove:
minimumairflow=100ft./min.
Verifying: Themaximumtemperaturerise 9.27 6.21=57.57
Themaximumcasetemperature 97.57 <100
Where: TheRcaisthermalresistancefromcasetoambience.
The Taisambienttemperatureandthe Tciscasetemperature.
d
d
d
P =Pi-Po=Po(1- )/
T=P Rca=
Tc=Ta+ T=
d
d