SEP 12, 2003 revised to OCT 26, 2006

Page 7 of 8

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QLS25 DC-DC Series Data Sheet

25A Quarter-Brick

engineering and understanding of the overall

safety requirements and should be performed by

qualified personnel.

Thermal Considerations

The QLS25 Series converters are designed for

natural or forced convection cooling. The maximum

allowable output current of the converters is

determined by meeting the derating criteria for all

components used in the converters. For example,

the maximum semiconductor junction temperature is

not allowed to exceed 120°C to ensure reliable long-

term operation of the converters. Contact Power-

One for the complete list of the derating criteria.

The graphs in Figures 10-12 show the maximum

output current of the QLS25 Series converters at

different ambient temperatures under both natural

and forced (longitudinal airflow direction, from pin 1

to pin 3) convection.

For example, from Figure 11, the QLS25ZE

operating at 55C can deliver up to 18A reliably with

100LFM forced air, while up to 25A reliably with

400LFM forced air.

0

5

10

15

20

25

25 30 35 40 45 50 55 60 65 70 75 80 85

Ambient Temperature (°C)

0

100LFM

200LFM

300LFM

400LFM

Figure 10. QLS20ZG (5V) Derating Curves

0

5

10

15

20

25

25 30 35 40 45 50 55 60 65 70 75 80 85

Ambient Temperature (C)

0

100LFM

200LFM

300LFM

400LFM

Figure 11. QLS25ZE (3.3V) Derating Curves

0

5

10

15

20

25

25 30 35 40 45 50 55 60 65 70 75 80 85

Ambient Temperature (C)

0

100LFM

200LFM

300LFM

400LFM

Figure 12. QLS25ZD (2.5V) Derating Curves