Thermal design questions

Thread Starter

Manden

Joined Dec 15, 2020
3
Hi I'm building a lab bench power supply and was wondering about the thermal design i have ordered a heatsink which should be adequite for the task . The question is how to install it, would it be best to install it with the fins sticking out of the back of my PSU and keep the ambient temperature mostly equal to the room temperature. Or would it be best to install the heatsink with the fins in the case and having a higher ambient but create airflow with a fan and possibly another fan pumping the hot air out of the case. it is worth noting that i plan to install both a voltae regulator(T0-220) and a power transistor(TO-3) on the heatsink.

I have tried google and youtube but can't find much on the topic.

Thanks in advance to anyone willing to help or maybe point me to a resource for this kind of knowledge.
 

dl324

Joined Mar 30, 2015
13,526
Welcome to AAC!

It's up to you. If you mount the heatsink on the back of the enclosure, you don't need vent holes and possibly a fan in the box.

What is the thermal resistance of the heatsink and junction to case for each device? How much power will each device be dissipating worst case? Do you expect ambient temperature to be significantly higher than 25C?
 

Thread Starter

Manden

Joined Dec 15, 2020
3
Welcome to AAC!

It's up to you. If you mount the heatsink on the back of the enclosure, you don't need vent holes and possibly a fan in the box.

What is the thermal resistance of the heatsink and junction to case for each device? How much power will each device be dissipating worst case? Do you expect ambient temperature to be significantly higher than 25C?
Thank you!

sink is is 1.75 C/W
The regulator is 3 - 4 C/W
And i haven't decided on a transistor yet but the once i'm looking at have a junction to case of 0.7 C/W



Worst case the transistor will dissipate 30W and the regulator 10W i have considered using two transistors in parralel but it seems hard to make them share current equally from what i gather.

If i keep the heatsink out of the case then no maybe very rarely in summer. If i have the heatsink in case i fear ambient temprature may get quite high. So i guess what I'm wondering is, is the trade off for airflow but high ambient worth it enough to spend money on fans.
 
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