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I want to make my own computer power supply.

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jdraughn

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From what I have read, all the -5v and -12v aren't needed on todays computers, so all I really need is 3.3v, 5v and 12v.

I need around 400 to 500 watts of output power. I am trying to build a portable PC that is kind of like a notebook, but is just plugged in. I am hoping to keep the thickness of the enclosure down to about 3". The power supply is really the only thing that i am having trouble with. I could go with a 1U power supply, but I am trying to keep size down and just want the bare amount of features that I need to make it work, and besides, I like building circuits.

I have seen a few circuits for power supplys on the web but don't really know whats appropriate for a PC. I imagine I need to stay with a switching power supply since I need to keep heat output down.

I could probably build 3 "seperate" power supplies, each with their own outputs (3.3v, 5v, and 12v) if that would make things easier. It would be easier to find a spot for 3 smaller circuit boards then 1 large one, thats for sure.

The design of the PCB is probably quite a bit simpler with more flexible options when they are 3 seperate boards too.

Does anyone know of any circuits that output pretty high watts that are very effecient and produce low EMI which makes it suitable for PC use?

I imagine I probably need around 25 to 30 amps output on the 12v, 10 to 15 amps for the 5v and around 10 amps for the 3.3 volt.

Other then the ATX connector, there are a few other power connectors (video card, hard drive, 4 or 6 pin additional connector on the motherboard) where I could probably make yet additional smaller boards to help split the load.

Any thoughts?
 
But it's not about just building any old power supply, I want one to so I can make my desktop PC smaller, lighter and easier to transport.

You don't feel a need to transport your desktop computer around like I do. My notebook with a 17" screen and GeForce 8800GTM with 4GB of memory is not adequate for what I want to do when im at work.
 
As suggested, it's completely pointless as far as cost goes - expect to pay ten to twenty times the cost of a bought supply building your own - not counting the amount of components you're going to destroy in the process.

I would suggest you buy an existing supply (which is a tiny fraction of the cost of it's parts), and strip the insides out of it. Your biggest problems are going to be cooling it (PC supplies use big fans because they need them), and safety aspects.
 
I had seen very small 200 watt power supplies that operate off of 12v dc for around 45.00 online. (used for miniITX motherboards) I was thinking of using 3 of those and then using an ac-dc adapater with adequate wattage to drive them. The boards looked so simple I thought I could just build my own rather then buy something pre made.
 
I had seen very small 200 watt power supplies that operate off of 12v dc for around 45.00 online. (used for miniITX motherboards) I was thinking of using 3 of those and then using an ac-dc adapater with adequate wattage to drive them. The boards looked so simple I thought I could just build my own rather then buy something pre made.

Are you capable of winding high frequency switch-mode transformers, to suitable high quality for safety reasons?.

Switch-mode PSU's aren't simple devices, and the slightest design flaw is almost certain to destroy it.
 
Thanks for the advice guys. This is basically what I was looking at getting. It's very small.

Would it be feasable to buy 2 or 3 of these and wire the outputs in parallel? Or I could use one to power the motherboard, one to power the video card, and one to power the drives and any other accessories.

I took a look at a online calculator where you enter your CPU and Video card, along with what accessories you have and it tells you how much power each component would require. My motherboard and CPU would require 200 watts, and the video card would require 200 watts. I am sure that the website had a wide margin of safety with those numbers too.

I think the hard part would be finding a ac adapter that can output enough amps to drive the 3 12v power supplies. The one im using for my notebook happens to have 19V output, which is within the specs of those power supplies, but only puts out 6 amps.

However, since these are regulated supplies and have a pretty wide input range, maybe I could look at building an old school non switching unregulated ac adapter.
 
That's how they did it in the old Altair days. That 8A (about 100W) supply weighed a ton.
Just buy a gaming notebook or a lanbox, they're going cheap these days.

That mini-itx supply won't power your rig, not even close.
 
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That's how they did it in the old Altair days. That 8A (about 100W) supply weighed a ton.
Just buy a gaming notebook or a lanbox, they're going cheap these days.

That mini-itx supply won't power your rig, not even close.

Thanks, but did you read my posts? I mentioned I had a notebook with 4GB of ram and a 8800GTS video card. Any notebook that has a more powerful video card then this starts at around 2k. I really need at least 6GB of memory too, but the only other options then 2 - 2GB sticks (which is what I have) is
Newegg.com - G.SKILL 8GB (2 x 4GB) 200-Pin DDR2 SO-DIMM DDR2 667 (PC2 5300) Laptop Memory - Laptop Memory which costs nearly 400.00 to go to 8GB.

I also mentioned going with 3 of those power supplys, not 1. My motherboard and quad-core CPU is actually able to run fine with a 200 watt mini itx powersupply that I already have, it's just once I start adding video card and multiple harddrives that it is not enough.
 
What could you possibly be running that needs that much power & be portable?

Where's the logic in building a bunch of power supplies (what are you going to put them in) that will weigh more than a small aluminum PC case with a 500W supply? Your gaming PC also requires very good ventilation or FAIL. This is a Lanbox style case. They're made for gaming rigs on the go.
**broken link removed**

PS the $400 to go to 8G is your best realistic bet.
 
What could you possibly be running that needs that much power & be portable?

I like to play multiple instances of World of Warcraft simutaneously, 5 to be exact. 6 GB of ram is "barely" enough, and that was before the latest expansion. This notebook is ok with 3, maybe 4 instances but I have to turn everything down all the way, and even so I still get very low frame rates because of the lack of having enough CPU and GPU power.

Where's the logic in building a bunch of power supplies (what are you going to put them in) that will weigh more than a small aluminum PC case with a 500W supply? Your gaming PC also requires very good ventilation or FAIL. This is a Lanbox style case. They're made for gaming rigs on the go.
**broken link removed**

PS the $400 to go to 8G is your best realistic bet.

Those power supplies were what, 2.5" x 2.5" x 1.5" and over 95% effecient? I know all about the problems with heat and was planning on having great ventilation. I was also planning on putting the AC to DC converter in a seperate container. Sure it would be big and heavy, but as far as the computer itself, it would be pretty small and light, which is the idea.

It sounds like all you want to do is argue with what I want to do, since you seem to be made out of money, and doing things in a DIY manner for fun and to save a few bucks is not your style. (Ironically I thought this was a DIY type of place, not a go buy a ready made solution).

I will find some place else to ask for help and won't bother you anymore with my unrealistic ideas.
 
Wow 6 copies of Warcraft at once is it more fun? Why portable though? Are you one of those fellows who makes real money selling Warcraft gold on eBay?

OK, well building your own 400W switchmode supply is unrealistic and very costly plus would be larger than simply taking an existing $50 one apart.

That lan case requires assembly a form of DIY, it's not expensive they can be found for about $100.
**broken link removed**
 
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It sounds like all you want to do is argue with what I want to do, since you seem to be made out of money, and doing things in a DIY manner for fun and to save a few bucks is not your style. (Ironically I thought this was a DIY type of place, not a go buy a ready made solution).

But you're not saving a few bucks, you're likely to be spending a LOT more than buying a ready made solution.

DIY is pointless when it's considerably more expensive than a ready made solution.
 
Does it really cost $15 a month to play warcraft online? That's times six. $90 per month and you think the rather simple & elegant $400 RAM upgrade is expensive?
 
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