DS_FL75L07_02162012

3

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 Testing Setup

Delta’s filter 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 filter 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 6.35mm (0.25”).

Thermal Derating

Heat can be removed by increasing airflow over the

module. Figure 4 shows maximum output is a function of

ambient temperature and airflow rate. 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.

Note: Wind Tunnel Test Setup Figure Dimensions are in millimeters and (Inches)

10 (0.4”)

MODULE

AIR FLOW

50.8 (2.0”)

FACING PWB

PWB

AIR VELOCITY

AND AMBIENT

TEMPERATURE

MEASURED BELOW

THE MODULE

Figure 4: Wind tunnel test setup

THERMAL CURVES

Figure 5: Temperature measurement location

The allowed maximum hot spot temperature is defined at 115

℃

FL75L07 A (Standard) Output Current vs. Ambient Temperature and Air Velocity

@ Vin = 48V (Either Orientation)

0

1

2

3

4

5

6

7

8

25

35

45

55

65

75

85

Ambient Temperature (℃)

Output Current (A)

300LFM

Natural

Convectio

200LFM

100LFM

Figure 6: Output Current vs. Ambient Temperature and Air

Velocity @ Vin = 48V (Either Orientation)