THERMAL CONSIDERATIONS Thermal Derating
Thermal management is an important part of the system
design. To ensure proper, reliable operation, sufficient
cooling of the power module is needed over the entire
temperature range of the module. Convection cooling is
usually the dominant mode of heat transfer.
Heat can be removed by increasing airflow over the module.
The module’s maximum case temperature is 110℃. To
enhance system reliability, the power module should always
be operated below the maximum operating temperature. If
the temperature exceeds the maximum module
temperature, reliability of the unit may be affected.
Hence, the choice of equipment to characterize the
thermal performance of the power module is a wind
tunnel.
Thermal Testing Setup
Delta’s DC/DC power modules are characterized in
heated vertical wind tunnels that simulate the thermal
environments encountered in most electronics
equipment. This type of equipment commonly uses
vertically mounted circuit cards in cabinet racks in which
the power modules are mounted.
The following figure shows the wind tunnel
characterization setup. The power module is mounted
on a test PWB and is vertically positioned within the
wind tunnel. The space between the neighboring PWB
and the top of the power module is constantly kept at
6.35mm (0.25’’).
Figure 21: Temperature measurement location
The allowed maximum hot spot temperature is defined at 110
℃
Note: Wind Tunnel Test Setup Figure Dimensions are in mil limeters and (Inches)
12.7 (0.5”)
MODULE
A
IR FLO
W
50.8
(
2.0”
)
FACING PW
B
PWB
AIR VELOCIT
Y
AND AMBIEN
T
TEMPERATUR
E
MEASURED BELO
W
THE MODUL
E
0
50
100
150
200
250
300
350
400
25 35 45 55 65 75 85 95 105
Output Power (W)
Hot Spot Temperature(℃)
H48SN28012NR A (Standard) Output Power vs. Hot Spot Temperature
(Either Orientation)
Figure 22: Output power vs. hot spot temper ature (Either
Orientation)
Figure 20: Wind Tunnel Test Setup
H48SN28012_01172008
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