Convert an AC PSU to run on DC???

[settra]

Hello forum, i was wandering, since most of the PC PSU's are switching, and since they all use a Rectifier, to convert the AC to some kind of DC,
is there a way, change some of the PSU components, to make it run from an unregulated DC source?? (a car battery maybe?)

 

[Nigel Goodwin]

Hello forum, i was wandering, since most of the PC PSU's are switching, and since they all use a Rectifier, to convert the AC to some kind of DC,
is there a way, change some of the PSU components, to make it run from an unregulated DC source?? (a car battery maybe?)

Put 25-30 car batteries in series and many SMPSU's will work without any changes.

 

[HiTech]

Maybe I don't understand your reasoning here. Why not just use a car battery and voltage dividers to achieve the desired DC voltages? A switching PSU is going to have some efficiency loss added to the end result, so why bother?

 

[settra]

1) it is more like a "can it be done" thing, and not a neccecity
2)if i do it, i would do it, to power Car pc , so, i cant use voltage dividers (which anyway have smaller efficiency?? )

 

[Nigel Goodwin]

1) it is more like a "can it be done" thing, and not a neccecity
2)if i do it, i would do it, to power Car pc , so, i cant use voltage dividers (which anyway have smaller efficiency?? )

Use a car PC PSU - which is what you would be making if you extensively modified a mains PSU to run off 12V.

 

[NorthGuy]

For PC you need good 12V and 5V power, negative too. Car battery is unregulated. It may go from as low as 9V when cranking to as high as 15V when charging. Standard PC PSU starts from rectified mains, which is 150 to 350V, depending on the country. I wouldn't expect much of it to be reusable, better build/buy a new one.

 

[settra]

but, if you take the PSU's circuit, after the RECtifier, it's only DC. so, if you remove the rectifier, and just supply DC to its outpout, isint this supposed to work??? i suppose you have to add the exact voltage as was the rectifiers outpout?? (which i have no idea how much is?? )

 

[NorthGuy]

but, if you take the PSU's circuit, after the RECtifier, it's only DC. so, if you remove the rectifier, and just supply DC to its outpout, isint this supposed to work??? i suppose you have to add the exact voltage as was the rectifiers outpout?? (which i have no idea how much is?? )

You do not really need to remove the rectifier. It won't hurt much. But you need to apply a high voltage. Read Nigel's post #2.

 

[Nigel Goodwin]

but, if you take the PSU's circuit, after the RECtifier, it's only DC. so, if you remove the rectifier, and just supply DC to its outpout, isint this supposed to work??? i suppose you have to add the exact voltage as was the rectifiers outpout?? (which i have no idea how much is?? )

You should, as I've already effectively told you - and as NorthStar mentioned, there's no need to remove the rectifier.

There's no need for the exact voltage though, as it has a very wide range.

It does depend on the exact design, as some will only work off AC (the startup system sometimes is AC only).

 

[settra]

ooo. i though nigel on post #2 was trolling
for some reason, i though that rectifiers outpouted only like, 2-3 volts... but if i need way more than 12 volt, then i would need an extra dc-dc converter.... (so why not just use a dc-ac one).
how much volt approximately??

 

[alec_t]

but, if you take the PSU's circuit, after the RECtifier, it's only DC. so, if you remove the rectifier, and just supply DC to its outpout, isint this supposed to work?

It won't work because of the current needed. Suppose your PSU draws 4A at 120V input. To get the same power from a 12V battery you'd have to draw 40A. The wiring and components inside the PSU aren't designed to handle that.

 

[Nigel Goodwin]

ooo. i though nigel on post #2 was trolling
for some reason, i though that rectifiers outpouted only like, 2-3 volts... but if i need way more than 12 volt, then i would need an extra dc-dc converter.... (so why not just use a dc-ac one).
how much volt approximately??

No disrespect, but if you know so little about electronics then you're rather doomed to failure.

The DC is simply rectified mains, so for your 220V about 310V DC - this is incredibly basic stuff.

You can buy specific in-car PC power supplies, I would VERY strongly suggest you do so.

Here's one of many such available: