UVQ-12/10-D48P-C Murata Power Solutions Inc, UVQ-12/10-D48P-C Datasheet - Page 19

• Manufacturer Part Number: UVQ-12/10-D48P-C
• Description: DC/DC TH 10A 48-12V Q-Brick
• Manufacturer: Murata Power Solutions Inc
• Series: UVQr

Specifications of UVQ-12/10-D48P-C

• Dc / Dc Converter O/p Type: Single
• No. Of Outputs: 1
• Input Voltage: 36V To 75V
• Power Rating: 120W
• Output Voltage: 12V
• Output Current: 10A
• Approval Bodies: EN / IEC / UL
• Supply Voltage: 48V
• Rohs Compliant: Yes
• Product: Isolated
• Output Power: 120 W
• Input Voltage Range: 36 V ot 75 V
• Input Voltage (nominal): 48 V
• Number Of Outputs: 1
• Output Voltage (channel 1): 12 V
• Output Current (channel 1): 10 A
• Isolation Voltage: 2.25 KV
• Package / Case Size: Quarter Brick
• Lead Free Status / Rohs Status: Details

Calculating Maximum Power Dissipation
To determine the maximum amount of internal power dissipation, fi nd the
ambient temperature inside the enclosure and the airfl ow (in Linear Feet per
Minute – LFM) at the converter. Determine the expected heat dissipation
using the Effi ciency curves and the converter Input Voltage. You should also
compensate for lower atmospheric pressure if your application altitude is
considerably above sea level.
The general proceedure is to compute the expected temperature rise of the
heatsink. If the heatsink exceeds +100°C. either increase the airfl ow and/or
reduce the power output. Start with this equation:
where “Ta” is the enclosure ambient air temperature and,
where “Ts” is the heatsink temperature and,
where “RΘ [at airfl ow]” is a specifi c heat transfer thermal resistance (in
degrees Celsius per Watt) for a particular heat sink at a set airfl ow rate. We
have already estimated RΘ [at airfl ow] in the equations above.
Note particularly that Ta is the air temperature inside the enclosure at the
heatsink, not the outside air temperature. Most enclosures have higher
internal temperatures, especially if the converter is “downwind” from other
heat-producing circuits. Note also that this “Pd” term is only the internal heat
dissipated inside the converter and not the total power output of the converter.
We can rearrange this equation to give an estimated temperature rise of the
heatsink as follows:
www.cd4power.com
Heatsink Kit *
Model Number
HS-QB25-UVQ
HS-QB50-UVQ
HS-QB100-UVQ
* Kit includes heatsink, thermal pad and mounting hardware.
Internal Heat Dissipation [Pd in Watts] = (Ts – Ta)/RΘ [at airfl ow] [6]
Ts = (Pd x RΘ [at airfl ow]) + Ta [7]
®
Still Air (Natural convection)
thermal resistance
10.6°C/Watt
12°C/Watt
8°C/Watt
Heatsink height
0.25" (6.35mm)
0.50" (12.7mm)
1.00" (25.4mm)
(see drawing)
Low-Profi le, Isolated Quarter-Brick 2.5-40 Amp DC/DC Converters
Heat Sink Example
Assume an effi ciency of 92% and power output of 100 Watts. Using equation
[4], Pd is about 8.7 Watts at an input voltage of 48 Volts. Using +30°C ambient
temperature inside the enclosure, we wish to limit the heat sink temperature
to +90°C maximum baseplate temperature to stay well away from thermal
shutdown. The +90°C. fi gure also allows some margin in case the ambient
climbs above +30°C or the input voltage varies, giving us less than 92%
effi ciency. The heat sink and airfl ow combination must have the following
characteristics:
Since the ambient thermal resistance of the heatsink and pad is 12.5°C/W, we
need additional forced cooling to get us down to 6.9°C/W. Using a hypothetical
airfl ow constant of 0.005, we can rearrange equation [5] as follows:
or,
and, rearranging again,
162 LFM is the minumum airfl ow to keep the heatsink below +90°C. Increase
the airfl ow to several hundred LFM to reduce the heatsink temperature further
and improve life and reliability.
(Required Airfl ow, LFM) x (Airfl ow Constant) = RΘ[Nat.Convection] /
RΘ[at airfl ow] –1
(Required Airfl ow, LFM) x (Airfl ow Constant) = 12.5/6.9 –1 = 0.81
8.7 W = (90-30) / RΘ[airfl ow] or,
RΘ[airfl ow] = 60/8.7 = 6.9°C/W
(Required Airfl ow, LFM) = 0.81/0.005 = 162 LFM
Dimensions in inches (mm)
Optional Heatsink
UVQ Series
UVQ Series
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