LM317 in parallel - Answered -> LM2596 circuit question

Danteo I have used Webench to easily find a schematic for my specs but, as I said, many components can't be found or must be order in 500+ quantities, don't know if it is possible to order samples from TI since I don't work in a big company (I only have a sole proprietorship business) and I'm located in Finalnd, but I will check.

Sheldon the LM2596 seems to be a good choise, since I can find already assembled circuits using it even on eBay for not more than 4€, seems that I will order a bunch of them since they are adjustable and use them in my other projects too.

I actually found an assembled LM2596 circuit in a really small package from a Chinese eBay seller for only 1.05 pounds with free postage, with 1 year warranty, ordered 5 of them :-P

Well since I found a better solution for my problem, only one question remains, what would be the ideal placement of a heatsink to this board (since if using it with a greater than 15W load it is recomended) would I have to only cool the chip or the whole unit, by the way this will be placed inside a solid aluminum small box measuring about 8x5x5cm , would it be better to mill the block so that it fits exactly inside, so the case itself is a heatsink, or do you believe it would get too hot.

Module photo:

it looks like the regulator is heatsunk through the ground plane. the switching regulators are much more efficent than a linear regulator. a moderate air flow around the board should do the trick.

I invented the Lm317.   It is NOT designed to be paralleled. If you parallel devices, one will supply all the current until it thermally or current limits and then the other one will come on.  This not reliable.

The data sheet show circuitry that allow paralleling by forcing current sharing. A new device, the LT3081 is designed for easy sharing. Also the LT 3080

Bob Dobkin

welcome to the forum Bob!

what r u talking about????

Hi all,

I agree with all comments, better the LM2596 than a linear regulator, probably you would have loses about 15W with linear, so switched mode power supply will be better, because of the battery lifetime, and for the heatsink that would be needed.

The module you show, looks great!! But in order to calculate the heatsink you need, we must know the efficientcy of this module, in order to know the power loses.

Also as Sheldon says it seems to be heatsunk through the ground plane, furthermore if the manufacturer recommends heatsink, probably it will recommend how mount it, or which surface must be in touch with the heatsink.

Do you have a link or the datasheet of the module? Even, you should know how much heat can the external box disipate?

But, step by step, first we have to know the efficientcy and the loses, so a datasheet would be great.

I hope I could help.

Let us know how your project goes on.

Regards,

Miguel

Talk about stright form the horses mouth - nice one Bob, you have been responsible for many a power supply project....just goes to show how well your design as stood the test of time...

Gerry

Bob [Bob Dobkin], your reply in this forum seems largely unnoticed. Thank you for inventing the LM317 and creating such a useful device [and revenue engine] that I am just now learning about. And thank you for suggesting the newer LT3081 and LT3080 as alternatives when needing more current than one LM317 can provide.

Regarding voltage sources in general I think putting battery cells in parallel also has problems. The cells will eventually drain each other unless something is done to prevent that.