HBR Series of Railway Half-Brick
[Type text]
[Type text]
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Up to 150 Watts DC-DC Converter
AIR FLOW RATE
TYPICAL Rca
The following curve is the de-rating curve of HBR series with heat sink
Natural Convection
20ft./min. (0.1m/s)
3 ℃/W
100 ft./min. (0.5m/s)
200 ft./min. (1.0m/s)
300 ft./min. (1.5m/s)
400 ft./min. (2.0m/s)
1.44 ℃/W
1.17 ℃/W
1.04 ℃/W
0.95 ℃/W
Example (with heat sink M-C092):
What is the minimum airflow necessary for a HBR113S5-30 operating at nominal line voltage, an output current of 30A, and a maximum ambient
temperature of 40℃?
Solution:
Given:
Vin=110Vdc, Vo=5Vdc, Io=30A
Determine Power dissipation (Pd):
Pd=Pi-Po=Po(1-η)/η
Pd=5.0×30×(1-0.925)/0.925=12.16Watts
Determine airflow:
Given: Pd=12.16W and Ta=40℃
Check above Power de-rating curve:
Pd<20W, Natural Convection
Verify:
Maximum temperature rise is
△T = Pd × Rca=12.16×3=36.48℃
Maximum case temperature is
Tc=Ta+△T=76.48℃ <100℃
Where:
The Rca is thermal resistance from case to ambient environment.
Ta is ambient temperature and Tc is case temperature.
September 16 -2017 A.04
Page 7 of 15
DATEL [ DATEL, Inc. ]
