THERMAL CONSIDERATIONS
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.
Hence, the choice of equipment to characterize the
thermal performance of the power module is a wind
tunnel.
Thermal Derating
Heat can be removed by increasing airflow over the module.
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.
THERMAL CURVES
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:
Hot spot temperature measured point
＊
FACING PWB
PWB
MODULE
4.5
Output Current (A)
The allowed maximum hot spot temperature is defined at 130
℃
L36SA12004(standard) Output Current vs. Ambient Temperature and Air Velocity
@Vin = 48V (Either Orientation)
4.0
3.5
AIR VELOCITY
AND AMBIENT
TEMPERATURE
MEASURED BELOW
THE MODULE
AIR FLOW
Natural
Convection
100LFM
200LFM
300LFM
400LFM
500LFM
3.0
2.5
50.8 (2.0”)
2.0
1.5
1.0
12.7 (0.5”)
Note: Wind Tunnel Test Setup Figure Dimensions are in millimeters and (Inches)
0.5
0.0
30
35
40
45
50
55
60
65
70
75
80
85
Ambient Temperature (
℃
)
Figure 20:
Wind tunnel test setup
Figure 22:
Output current vs. ambient temperature and air velocity
@V
in
=48V (Either Orientation)
DS_L36SA12004_02142007
11
DELTA [ DELTA ELECTRONICS, INC. ]
