ATX psu help - i just need a 100A 12V psu

[aq_mishu]

parallel atx psu

anyone please tell me what should i do for the following:

i just need a 100A 12V psu. For light weight and easyness, i'm planning to use ATX PSUs. These are SMPS right?? Now I have PSUs for @ 12V, 20A Max. So I can use 5 PSUs tied togather in a buss-bar. So total 12V 100A. Right?? i mean so simple... tie all of the 12V outputs of all the 5 psus all togather?? or some other thing also... it must be 12V and not less than that...

 

[diegobb]

Re: ATX psu help

I think that connecting two power supplies in parallel is not a good idea.
I don't know almost anything about switched PSU, but this is a general rule: "Don't connect two power supplies in parallel".

If one PSU output has a slightly lower voltage than the other, then you have a current going into the first one and that's not good at all.

Regards, Diego.

 

[aq_mishu]

Re: ATX psu help

that's what i was worried for... i think i can use a bunch of diods for making it directional... but you know... too many diods... 1N54xx will deliver max 3A... thus for each 20A @ 12V, i need 7 diodes.... and total it will be 42 diodes... other wise varactor (power diode..) but i have no idea on it and it is also kinda expensive here... and have no idea on fwd volt...

 

[diegobb]

Re: ATX psu help

Well, i think that connecting two diodes in parallel (I mean, connecting two diodes rated at 0.5A, to get a new one rated at 1A) is a bad idea, too. (Damn, i hate to be the "guy of the bad news")

The problem is that, a little diference in the parameter "Is", can produce a big diference in the resulting Id when the diodes are in parallel and at the same voltaje (Remember that Id=Is*(e^(Vd/n*Vt)-1), where Is ≈ 10^-15). One of the diodes can get, more current than the others, just because they are a little different.

You can try it with two 1N4148, one 5V source, one resistor and a digital multimeter.

I don't think this problem will have an easy and cheap solution ... if you're working with little currents, maybe you can try (I mean the parallel diodes, not the paralleled PSU), but i think that 100A is a lot.

Can't you break the system in some separated parts?
Maybe if you explain what are you trying to do, someone can help you.

Regards, Diego.

Added after 26 minutes:

After some time searching in internet trying to help, i found this: **broken link removed**.

I think you need a mix between Figure 32, and Figure 33, but i'm not sure this will work for your particular case. Maybe you can try with a little load to see how it work, and slowly increment it, to see what happens. Please be very carefull!

Regards, Diego.

 

[Awarapunshee]

Re: ATX psu help

Working with high power SMPS without any experience of SMPS is not a good idea, but anyway try this link, it may help you. Or google it ofcourse.

http://www.qrp4u.de/docs/en/smps_new/index.htm

ENJOY!

 

[aq_mishu]

ATX psu help

well, i need an hf+vhf rig. total current needs about 80A @ 13.8V. for 12V, i'm considering 100A total. and smps because of light weight... because this will time to time i have to move....

 

[snafflekid]

Re: ATX psu help

That is a LOT of power, 1200W. You can connect some cables from your car while it is running!

You cannot put power supplies in parallel and expect it to work correctly. You could try to design your own, but 1200W ps probably needs some experience (it needs to be efficient or it will be too hot to touch)

 

[aq_mishu]

ATX psu help

help.... you know the 1 psu for the entire rig... too many items in a place thus one single psu... linear is bulky... thus smps... if you guys can help... at least 40A 13.8v x 2 in parallel with protection diode... because for each equipment, @ 12v, 25 A. each...