| cowanrg |
ok, usually google gives a ton of hits for eveverything. you could put in "frying pan no pants circus banana" and get 200,000+ hits. well, "linear computer PSU" gets 0 hits. i searched around for awhile and it seems no one has tried to do a linear ATX power supply.
i understand its sort of silly, but maybe there are benefits. there is a thread over on audiogon that suggests a linear power supply will make your computer sound and look better, because of cleaner power. well, ill bite i guess. it makes enough sense, being that computer PSU's arent that great, they are probably VERY noisy (RF and electrical noise).
im willing to give it a shot. how would you guys design it? and do you think it would be possible to build a ~300-500W linear PSU in ATX form factor specs? (150mm x 140mm x 86mm). it would be TIGHT. basically, all you need is +3, +5, and 2 +12v lines.
external is always an option, but keeping it small would make for a neat solution. |
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| mateo88 |
| I've definitely thought of doing this, but decided it would just be way too inefficient. Figured it would probably help with overclocking somehow and be great for computers meant for audio. I really don't think there's any way it could be done in ATX specs. Even if it was possible to fit all the parts in the case, it would overheat so ridiculously fast it's not even funny. |
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| luka |
Hi
It is inefficient and it has bad regulation if you use just caps, trafo,diods. But if you use some sort of regulators it will be still too big to put anywhere, because you have high currents. |
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| AndrewT |
Hi,
a series linear regulator dissipates a lot of heat when delivering lots of current.
Series regs run cooler when the current demand is lower and almost cold at zero output current.
What proportion of the time does a computer demand maximum current from all the supplies at the same time?
What is the real power consumption on EACH of the voltage supplies during normal running?
I suspect those 250W to 300W PSUs are ticking over at less than 50W for 90% of the time. |
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| cowanrg |
yeah, those were the problems i was encountering in thinking how it would work...
does it HAVE to be regulated? im guessing and unregulated linear supply wouldnt be that much better than a traditional ATX supply...
my guess is that it would have to be external. if that was the case, you could just cheat and do multiple 3A voltage regulators in parallel right? so, for the 30A lines, just do 10 regulators. sure, its not elegant, but it would work and be relatively simple. and since it would have its own case, you could use large heatsinks and just use separate transformers for each voltage requirement. |
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| cowanrg |
| quote: | Originally posted by AndrewT
Hi,
a series linear regulator dissipates a lot of heat when delivering lots of current.
Series regs run cooler when the current demand is lower and almost cold at zero output current.
What proportion of the time does a computer demand maximum current from all the supplies at the same time?
What is the real power consumption on EACH of the voltage supplies during normal running?
I suspect those 250W to 300W PSUs are ticking over at less than 50W for 90% of the time. |
i had that in the back of my mind... my home theater computer only uses a 330 watt power supply. it runs just fine and is stable as can be. it doesnt have a bunch of hard drive (none, in fact, just 2 flash drives for the OS). the only thing it powers is the motherboard and graphics card. and it doesnt even use fans, so it doesnt have to power a cooling system.
my guess is you could get away with a 300-500 watt supply for most high end audio/video PC's. |
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| luka |
Hi
| quote: | | does it HAVE to be regulated? im guessing and unregulated linear supply wouldnt be that much better than a traditional ATX supply... |
That is not true. It has to be regulated, and very good. In computer there are many things that depend on "solid" voltage, that is why you can't use/have unregulated supply.
| quote: | | I suspect those 250W to 300W PSUs are ticking over at less than 50W for 90% of the time. |
I don't aggre with you. It all depends on what you have inside. Like I have dual core proc., graphic card for playing games from time to time, hard drives (many people more than 2), fans,....
So 50w in my case is to low value, but since I have 400w supply it is not working with that power, more like 100-150w. I can't but someone else could measure how much power does computor need. |
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| Tweeker |
It might be feasable to use transformer based supply feeding switching regulators, though I wouldnt want to try and fit it in an atx psu form factor. A few critical linear regulators could be fed off another winding.
| quote: | | my guess is that it would have to be external. if that was the case, you could just cheat and do multiple 3A voltage regulators in parallel right? so, for the 30A lines, just do 10 regulators. sure, its not elegant, but it would work and be relatively simple. and since it would have its own case, you could use large heatsinks and just use separate transformers for each voltage requirement. |
If those regs were LM338s, youd be burning 900+ watts just for the 30A lines. Battery power begins to look sensible.
How about throwing several farads and some batteries at the problem of regulation and varying loads? |
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| luka |
Hi
Battery would be good, but even battery sags more than you would want + you would need 2. One small for -12 and -5 volts |
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| Eva |
You should rather forget about such a thing as a linear computer PSU. The computer itself is far noisier than any SMPS, particularly onboard audio is the noisiest thing in the world and the resulting linear PSU will be bigger and heavier than the own computer itself, like a 300W calss A amplifier. Furthermore, very thight regulation is required at least in the +5V and +3.3V rails, and with modern CPU and video chipsets you should expect at least 200W to be drawn continuously while the computer is performing some task.
A simple way to get a very low noise floor is to use an external sound card, although not all of them feature galvanic isolation thus leading to ground loops. This may be solved by taking advantage of digital optical outputs or coaxial outputs with transformer coupling. |
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| davidallancole |
There are real small form factor computers you could use that could be run off of batteries or a linear regulated supply, though it would still be pretty beefy. They use a dc to dc converter to get all the levels and can be run from 12 volt lines (I think meant for car applications). I wish I could remember the website for these little computers.
The thing with linear power supplys is this; if you want big power (say 75 watts), you will need big heatsinks, pass transistors and what not. We had power supplies at work that put out a solid plus/minus 15 volts at 5 amps. Thats ~ 75 watts into a load. This thing was a foot and a half in all dimensions and weight 65 lbs. The whole backside was a heatsink. A linear power supply to make the same requirements of a switching supply for a computer would probably wind up being bigger than the computer. |
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| Korrah |
| quote: |
i understand its sort of silly, but maybe there are benefits. there is a thread over on audiogon that suggests a linear power supply will make your computer sound and look better, because of cleaner power. well, ill bite i guess. it makes enough sense, being that computer PSU's arent that great, they are probably VERY noisy (RF and electrical noise). |
Well... if you want a PC's features + a good linear power supply, wouldn't it be a lot easier to use a laptop? |
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| Eva |
| Every laptop includes a complex SMPS built in... And they may draw as much as 100W during strong CPU and disk activity... |
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| cowanrg |
everyone claims a computer is noisy and this noise destroys audio. i use a computer for all my music and dvd's now, and it seems pretty quiet. i leave my amps on all the time, there is NOTHING coming from the speakers (no hissing or noise). also, the noise floor on cd's is MUCH better than any of the other high end gear ive owned. and im using a computer's analog out to directly drive amplifiers...
so it sounds like a linear computer supply might be nearly impossible. bummer. any way to make the switching one better? |
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| cowanrg |
| quote: | Originally posted by Korrah
Well... if you want a PC's features + a good linear power supply, wouldn't it be a lot easier to use a laptop? |
no no no, laptops dont have the features i want. im talking about dedicated computers used for high end audio. laptops still have fans, spinning drives, and you cant put a nice soundcard into them (just a firewire or usb one... |
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| mateo88 |
| Maybe make a nice linear-regulated power supply just for the soundcard? Seems easy enough to do and wouldn't take much power at all. Or get a mini itx board that draws very little power as well and base a high end audio pc around that. |
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| Eva |
| quote: | Originally posted by cowanrg
everyone claims a computer is noisy and this noise destroys audio. i use a computer for all my music and dvd's now, and it seems pretty quiet. i leave my amps on all the time, there is NOTHING coming from the speakers (no hissing or noise). also, the noise floor on cd's is MUCH better than any of the other high end gear ive owned. and im using a computer's analog out to directly drive amplifiers...
so it sounds like a linear computer supply might be nearly impossible. bummer. any way to make the switching one better? |
Of course, a 50dB signal to noise ratio may be enough for most people... |
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| 4fun |
Hi!| quote: | | Of course, a 50dB signal to noise ratio may be enough for most people |
That's low....down to tape cassette level without any noise reduction. :bigeyes:
Although some built in (on motherboard) sound "cards" are terrible, easy to hear network and USB traffic etc, beware of such low level performance.
http://www.clarisonus.com/Research%...soundCards.html
I have myself the 2496 PCI card, and can hardly hear any noise (ear next to tweeter) even if I crank the volume up, not even hum as experienced in test the test above. Dead quiet in listening position.
Of course, a decent sound card has local voltage regulators in order to perform well. |
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| cowanrg |
| quote: | Originally posted by Eva
Of course, a 50dB signal to noise ratio may be enough for most people... |
nice contribution to the thread.
my sound card's SNR is 117dB. |
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| cowanrg |
| quote: | Originally posted by mateo88
Maybe make a nice linear-regulated power supply just for the soundcard? Seems easy enough to do and wouldn't take much power at all. Or get a mini itx board that draws very little power as well and base a high end audio pc around that. |
that is a possibility. interfacing it with the PCI card would be difficult, but doable. the following link shows the pinout. so, could make an adapter that could power just a single PCI slot.
http://pinouts.ru/Slots/PCI_pinout.shtml |
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| Eva |
| 50dB is the usual real-world SNR in laptops and onboard sound solutions, although earth loops can make it substantially worse... |
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| Korrah |
| quote: | Originally posted by Eva
Every laptop includes a complex SMPS built in... And they may draw as much as 100W during strong CPU and disk activity... |
Urm, if I'm reading this right, does it mean a laptop's batteries are capable of putting out more than 100W during high CPU/HDD activity?
| quote: |
no no no, laptops dont have the features i want. im talking about dedicated computers used for high end audio. laptops still have fans, spinning drives, and you cant put a nice soundcard into them (just a firewire or usb one... |
There are a few very nice USB/Firewire soundcards out there, pity Lynx isn't making any. |
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| mr.duck |
Hi, some of you are over estimating how much power a PC uses. A fully modern, high end gaming PC will draw ~250W from the wall typical when under load. But you can get silly and push this up to 400W or more quite easily with multiple graphics cards. About 85% of this 250W is drawn from the 12v power rails I think.
The PC I'm using right now should be drawing around 15W (not including monitor of course). So I expect it will be drawing around 20W or so from the wall (I'll be surprised if its more than 25W) |
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| ssmith |
cowanrg,
I'm also using my PC for all my audio too and am very happy. I had also (briefly) thought of a linear supply, but the thought of making something with bang-on 3.3v, 5v and 12v is too daunting.
Perhaps, however, they may be a way to mod an existing decent quality SMPS to make it cleaner/quieter? -- upgrade/add caps, shielding etc?
I'm currently using a Tagan 380w PSU, which is very nicely made and very quiet. I've compared to an older Antec PSU i had, and the only difference I could notice in audio was the fan noise.... |
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| SunRa |
Actualy a linear power supply could prove to have a sense if used with boards like this:
Intel Mini-Itx
VIA mini/nano/pico-ITX
All of these are enough for audio playback. Not for complex DSP like FIR filters and so on but enough for common audio aplications.
Here you may seen the poer consumption of a modern desktop CPU on 45nm technology. Now imagine the consumption for the mobile versions.
I think that used in conjuntion with small boards and with small power demandings, a linear PSU could proove worthing. Of course remains the problem of the the SMPS on the board, although I suspect that boards in the nano-itx format are using just the regulation provided by the powersupply unit. |
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| ifrythings |
| from what I can tell from Intels power supply spec. the psu would have to be able to handel a slew rate of 1A/uS. I don't a linear psu can do that (though I maybe wrong) |
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| Dave |
You can get above average quality computer power supplies that are ultra quiet (acoustic noise). Check out http://www.zalman.co.kr/ENG/Main.asp
Also with a conventional transformer you loose the benefits of active PFC. |
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| walkura |
Maybe that i misunderstand the datasheet i been reading .
(afterall there is a little difference between mcu or cpu)
But still the discussion intrested me and i looked up my own processor,s datasheet .
http://www.amd.com/us-en/assets/con..._docs/30430.pdf
At page 91 it states Vid & Idd is 1,30 volt @ 80 Amperes .
That makes a maximum thermal design power of 110 watt's .
The processor i have on my motherboard is a low power model but still consumes 65 Watt @ 1,30 Volt .
But i must say the idea is nice ,on one of my first pc's i placed a lineair powersupply .
(i blew up the smps by accidently switching it to 110 Volt)
But then again that was a 4,77 Mhz XT with an amazing 5 megabyte hard disc
:D |
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