I need a tiny tiny power supply

[HeXploiT]

I'm trying to find a very small psu for a project I'm doing.
It must have minimum 250w output and be AC.
The motherboard is a standard atx board.
Anyone have a clue where I can find something like this?
Also I don't mean small as in shuttle xpc small.
I need this to be small as in laptop psu small.

 

[Zap]

Typically the smaller PSUs are SFX or 1U sized. Any smaller than that and you'd have to go mini ITX, which will curtail the amount of power you can expect. What are you trying to run off it?

 

[HeXploiT]

Hopefully an 8800 series card and it'll be on a dual core system. The motherboard actually IS a mini-itx but I'm probably going to need more power than an itx psu can output to run this videocard. I actually have seen mini-itx psus that do 250-300watts(like this) but they're all dc. I'm not sure I'd even know how to convert something like that.
The thing is I'm making a mod and what I want is to be able to fit an entire gaming rig into ones back pocket. In other words size is everything. The fact that this might be difficult is what makes it fun.

 

[mooseracing]

I would go for a 1u PSU. My 350 iirc is 40mm high, about 4" wide and 6" long.

Also the one you linked shouldn't be thar hard to change. All the Pico PSU's are DC-DC then just use a power brick to get AC.

 

[mpilchfamily]

Your not going to get an 8800 series card to run off anything smaller then 400W. Really you need a nice 450W unit for even the 8800GT. The other 8800s require even more power. using a low wattage CPU helps to cut the power needs a bit but even then you need more then 300W. If you want to keep it small and low power you'll need to go with a low power video card as well.

The Mini-ITX PSUs are DC to DC so you would have to have a seperate AC to DC converter that can support those. All those units really do is take a single 12V input and break it down into the 5V and 3.3V a system needs. Thats why they are so small. The bulk of a PSU is for the AC to DC conversion.

 

[HeXploiT]

Originally posted by: mpilchfamily
Your not going to get an 8800 series card to run off anything smaller then 400W. Really you need a nice 450W unit for even the 8800GT. The other 8800s require even more power. using a low wattage CPU helps to cut the power needs a bit but even then you need more then 300W. If you want to keep it small and low power you'll need to go with a low power video card as well.

The Mini-ITX PSUs are DC to DC so you would have to have a seperate AC to DC converter that can support those. All those units really do is take a single 12V input and break it down into the 5V and 3.3V a system needs. Thats why they are so small. The bulk of a PSU is for the AC to DC conversion.

I ran a 7800gt oc on an overclocked xpc 250w power supply.
I'm not stating for a fact that this is going to work but I am saying it's not impossible. It's just a matter of finding what will work.
It's possible I might have to look into finding a very small motherboard that will support the laptop pcie-x standard. I think it's called mxm.
Not sure if anything like this even exists.

 

[mpilchfamily]

There is a big power difference between the 7800 and an 8800. So unless you miss stated the card series you where looking to use earlier a 250W to 350W PSU is not going to support a system running an 8800.

 

[nerp]

You might want to check out some Flex PSUs out there. There are some with 250+ watt and FSP even has some 80-plus ones. They might be tricky to fit in a standard case, though, but for a custom project it might be the ticket.

 

[mooseracing]

Originally posted by: mpilchfamily
The Mini-ITX PSUs are DC to DC so you would have to have a seperate AC to DC converter that can support those. All those units really do is take a single 12V input and break it down into the 5V and 3.3V a system needs. Thats why they are so small. The bulk of a PSU is for the AC to DC conversion.

The bulk is that but how come an ac/dc brick and a pico psu is so much small compared to say a 1u PSU of the same wattage?

Just out of curiousty how much juice does an 8800 need? I would expect the board/cpu/hard drive be at about 100 watts.

Is a larger PSU needed because only those provide the correct amperage on the rail or is a custom PSU needed that is still 200 watts but with on 12v rail that has the correct amp?

 

[mpilchfamily]

The recommendation for the average system running an 8800GT is about 26A to 28A on the 12V rails. So we are talking nothing smaller then a really good quality 400W PSU. A nice dual core system with everything but the video card needs between 150W to 180W. The 8800GT alone can pull upwards of close to 120W.

U1 PSUs and AC/DC bricks don't have to provide allot of power. So they can be smaller. If you open a 300W PSU and compare it to a 500W PSU there is allot more room in the case on the 300W. To support the power they have to use larger transformers, which are the largest components in the PSU. Not to mention the large capacitors required to help filter that power. AS you know AC is alternating current. If you don't have those filters some of the wavelength from the AC side can blead over to the DC side causing unclean or unstable power. This can damage the CPU and GPU real quick.

Now AC/DC bricks are much smaller because they are converting for only one voltage. Also they are converting that voltage in a different way. They also don't have to support the high amperage needs of a regular PSU. PSUs are called switching power supplies. The voltage and amperage from them will very quite a bit as a PC is running. It has to have the parts to help regulate that voltage and keep it within the ATX spec. When a PC jumps from a low to a high load the volatge can drop in a hurry and the PSU hase to keep up with that and maintain the proper voltage within +/-5%

 

[HeXploiT]

Just for the record the shuttle xpc SN68SG2 (250 watt) has on its support list support for at least a couple of 8800's.
http://global.shuttle.com/support_list03.jsp?PI=647