Fan selection - Electronic Circuits Projects Diagrams Free

Electronics4you · 13th February 2007, 10:48 AM

Hi there,

I have a circuit with four power MOSFETs. Near them (or on the heat sink) is placed a temperature sensor, which detects when the temperature is above a certain level. Now for the tricky bit...

How do a select the right fan/heat sink for the application?

I know the effect of the MOSFETs
I want to calculate the fan flow which is needed to cool down the MOSFETs faster than they heat up, so they don't cook.

Russlk · 13th February 2007, 01:08 PM

Unless you have applicable data on the heat sink, you will have to experiment.

Electronics4you · 13th February 2007, 01:16 PM

Do I need total area, thermal resistance, material...?

Russlk · 13th February 2007, 09:02 PM

Do I need total area, thermal resistance, material...?
No, you just have to make measurments and collect data.

audioguru · 13th February 2007, 09:30 PM

You just need the datasheet info for the heatsink, unless you made the heatsink by accident. You also need the datasheet info for the Mosfets.

kchriste · 14th February 2007, 05:01 AM

Quote:

Do I need total area, thermal resistance, material...?

Yes, and how much power will be dissipated by the MOSFETs (worst case), the max junction temp for the MOSFETs, any airflow restriction and what the working ambient temperature range will be. It can be pretty complicated and it is usually easier to determine this experimentally.

Electronics4you · 14th February 2007, 12:44 PM

Yes I know I need all that datasheets, but how do I calculate it?
I have no idea
Have you any examples?

kchriste · 15th February 2007, 04:40 AM

A quick Google of "heatsink design" turned up this:
http://sound.westhost.com/heatsinks.htm
And this:
http://www.flomerics.com/flotherm/te...apers/t226.pdf

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13th February 2007, 10:48 AM	#1
Electronics4you	Fan selection Hi there, I have a circuit with four power MOSFETs. Near them (or on the heat sink) is placed a temperature sensor, which detects when the temperature is above a certain level. Now for the tricky bit... How do a select the right fan/heat sink for the application? I know the effect of the MOSFETs I want to calculate the fan flow which is needed to cool down the MOSFETs faster than they heat up, so they don't cook.

13th February 2007, 01:08 PM	#2
Russlk	Unless you have applicable data on the heat sink, you will have to experiment. __________________ see my website: www.geocities.com/russlk

13th February 2007, 01:16 PM	#3
Electronics4you	Do I need total area, thermal resistance, material...?

13th February 2007, 09:02 PM	#4
Russlk	Do I need total area, thermal resistance, material...? No, you just have to make measurments and collect data. __________________ see my website: www.geocities.com/russlk

13th February 2007, 09:30 PM	#5
audioguru	You just need the datasheet info for the heatsink, unless you made the heatsink by accident. You also need the datasheet info for the Mosfets. __________________ Uncle $crooge

14th February 2007, 12:44 PM	#7
Electronics4you	Yes I know I need all that datasheets, but how do I calculate it? I have no idea Have you any examples?

15th February 2007, 04:40 AM	#8
kchriste	A quick Google of "heatsink design" turned up this: http://sound.westhost.com/heatsinks.htm And this: http://www.flomerics.com/flotherm/te...apers/t226.pdf __________________ Inside every little problem, is a big problem trying to get out. Last edited by kchriste; 15th February 2007 at 04:43 AM.