How Do DC Bricks Work

PSUs: The source of DC power for all components in the PC & often a big noise source.

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readk
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How Do DC Bricks Work

Post by readk » Wed Jan 20, 2010 11:11 pm

This is kind of an aside, but how do AC/DC power bricks work with DC/DC power supplies.

Right now I have a 150 watt Pico and a 150 watt (12v / 12.5a) brick. The brick gets pretty hot. Kill-a-watt ranges from 60 watts idle to 110 watts gaming and 145 watts in Furmark.

Even though the Pico is 150w would I get any benefit from connecting a Dell DA-2 I have lying around? Or would this provide too much power? Basically does the Pico PSU draw power from the brick or does the brick push power at the Pico? Would it be more heat efficient and less likely to catch fire or anything like that?

I also have the chance to exchange my 150 watt pico and get a M4-ATX which I think is simple to wire up to the DA-2 for me. But I don't really need the power do I, if the kill-a-watt says 110w when I'm gaming?

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Re: How Do DC Bricks Work

Post by qviri » Thu Jan 21, 2010 12:08 am

readk wrote:Even though the Pico is 150w would I get any benefit from connecting a Dell DA-2 I have lying around? Or would this provide too much power? Basically does the Pico PSU draw power from the brick or does the brick push power at the Pico? Would it be more heat efficient and less likely to catch fire or anything like that?
The AC/DC brick and the picoPSU work like any other electrical circuit out there. Just as the outlet in your wall doesn't push out power because it doesn't know if you'll plug in a 100 W incandescent bulb or a 5 W cell phone charger, the brick will only provide as much power as the devices down the chain (in this case: the computer components via picoPSU) draw.

I don't know what the specific efficiencies of the two bricks are, but generally speaking, more oversized is less efficient. Since your brick is rated for 150 W DC, and you measured with the kill-a-watt 145 W AC, you should have sufficient headroom once AC/DC conversion inefficiencies are calculated in. Unless you are considering a serious component upgrade that would result in much more power being drawn, or notice the brick getting unduly hot, I don't think there's much value in "upgrading" to the DA-2.
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readk
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Re: How Do DC Bricks Work

Post by readk » Thu Jan 21, 2010 12:47 pm

How hot should the brick get? I can put my hand on it, but just barely. Its like a cup of coffee that almost too hot to hold onto.

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Post by b_rubenstein » Thu Jan 21, 2010 3:11 pm

You should be able to keep your hand on it for 5 sec. without getting burnt. That's the standard test.

MtnHermit
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Post by MtnHermit » Thu Jan 21, 2010 4:00 pm

readk wrote:Right now I have a 150 watt Pico and a 150 watt (12v / 12.5a) brick. The brick gets pretty hot. Kill-a-watt ranges from 60 watts idle to 110 watts gaming and 145 watts in Furmark.
What components do you have connected (MB, RAM, HDD, CPU, VGA)? I'm considering getting a pico 150.
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readk
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Post by readk » Thu Jan 21, 2010 4:44 pm

MtnHermit wrote:
readk wrote:Right now I have a 150 watt Pico and a 150 watt (12v / 12.5a) brick. The brick gets pretty hot. Kill-a-watt ranges from 60 watts idle to 110 watts gaming and 145 watts in Furmark.
What components do you have connected (MB, RAM, HDD, CPU, VGA)? I'm considering getting a pico 150.
Gigabyte MA790XTA-UD4, 4Gb G.Skill 1.35v DDR3, Intel SSD, AMD 605e, Powercolor 5750

If I had to do it again I would get a faster processor and a slower/cooler video card. Maybe the 5750 Eco/Green edition or a GT220 or 240 fanless which I think use less power, and a 65w Intel Q9550s. Even if I had to get a stronger power supply, it would be worth it. Right now the CPU limits my system and the video card is a heat/power problem.

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Post by MtnHermit » Thu Jan 21, 2010 6:15 pm

readk wrote:Gigabyte MA790XTA-UD4, 4Gb G.Skill 1.35v DDR3, Intel SSD, AMD 605e, Powercolor 5750

If I had to do it again I would get a faster processor and a slower/cooler video card. Maybe the 5750 Eco/Green edition or a GT220 or 240 fanless which I think use less power, and a 65w Intel Q9550s. Even if I had to get a stronger power supply, it would be worth it. Right now the CPU limits my system and the video card is a heat/power problem.
That helps, my system is much more frugal, so I think the pico 150 would work well for me. Will likely use a 120W brick, roughly half the cost of the 150W.

GIGABYTE GA-H55M-UD2H, G.SKILL ECO 4GB 1.35V DDR3, 500GB Notebook HDD, Core i3-530 CPU using the IGP.

Had you considered OCing your 605e, yes it will increase the power but you should be able to get another 50%. BTW, doesn't your 5750 require a 6-pin PCIx connector? How did you do that with the pico?
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readk
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Post by readk » Thu Jan 21, 2010 8:36 pm

I used a 2x molex => 6 pin adapter. I'm not using the 2 molex for anything anyway.

I'm already about at the limit for power, if I had a more power-friendly video card I would consider oc the processor. As is, I don't want to use any more power. Also I am running fanless on the processor which is not exactly a recipe for overclocking.

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Post by electrodacus » Sat Jan 23, 2010 12:08 pm

MtnHermit wrote:
readk wrote:Gigabyte MA790XTA-UD4, 4Gb G.Skill 1.35v DDR3, Intel SSD, AMD 605e, Powercolor 5750

If I had to do it again I would get a faster processor and a slower/cooler video card. Maybe the 5750 Eco/Green edition or a GT220 or 240 fanless which I think use less power, and a 65w Intel Q9550s. Even if I had to get a stronger power supply, it would be worth it. Right now the CPU limits my system and the video card is a heat/power problem.
That helps, my system is much more frugal, so I think the pico 150 would work well for me. Will likely use a 120W brick, roughly half the cost of the 150W.

GIGABYTE GA-H55M-UD2H, G.SKILL ECO 4GB 1.35V DDR3, 500GB Notebook HDD, Core i3-530 CPU using the IGP.

Had you considered OCing your 605e, yes it will increase the power but you should be able to get another 50%. BTW, doesn't your 5750 require a 6-pin PCIx connector? How did you do that with the pico?
I can recommend my power supply for MtnHermit but not for readk because the video card will use to much power I also do not recommend the M4-ATX that is similar with the one I sell and it produce the 12V on board (this provide better 12V than the PicoPSU more stable but it will be limited so it will not help using a bigger brick). I sell a kit Y5 that is using a 150W fanless brick with 130W PSU see my signature for details.
[size=75][url=http://www.silentpcreview.com/forums/viewtopic.php?t=55153]PSU 130W fanless ATX $29.98 SALE[/url]
[url=http://www.silentpcreview.com/forums/viewtopic.php?t=55084]Quad Q8400s 2Ghz 0.925V Idle:31W load:49W[/url]
_______________________________________ [/size]

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Post by BillyBuerger » Sat Jan 23, 2010 3:17 pm

I'm wondering if it's even worth it for your system to be messing with picoPSU's and bricks. If your idle is 60W, a good/efficient ATX PSU wouldn't be far behind the pico at that range and would probably be better as you approach the limits of your pico and brick at 150W. For instance, a 300W 80+ bronze PSU would be about 82% efficient at 60W and 85% at your current max around 150W.

javitxi
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Post by javitxi » Sun Jan 24, 2010 7:07 am

I have purchased a 150W picoPSU + 150W power brick to this equipment:

Apex MI-008
Intel e5300 + Schyte Big Shuriken
Zotac GeForce 9300 I-E Wifi
2x2 gb of RAM
+ DVD-RW, x2 HDDs 3,5" I have already

Why 150W picoPSU +150W brick?

- it has 24 pin instead of 20 pin, and normally, if your system draw not so much energy, it wouldn't be a real problem that you lack of those connections. By the way, I'll prefer to have the complete 24 pin just in case, and also the difference in price between 120W-20 pin and 150W-24 pin it's ~10$.

- readk, if you have read the instructions of 150W picoPSU, it is said:

> for fanless operation de-rate the output of the 3,3V and 5V rails by ~35% or ensure PSU surface temperature should not exceed 65ºC, whichever comes first

5V and 3,3V are rated to 6A max load, so de-rating them means to have a 3,9A max load. I think I wouldn't draw more than 3,9A as you can see in the next point

> combined and sustained output should not exceed 65% of total power or ensure PSU surface temperature shoould not exceed 65ºC, whichever comes first.

So 150W x 0,65 = 97,5 W ~ 100W. My system would draw with prime95+orthos /3dmark probably no more than 90-100W as far as I've read on many configurations of many users around this and others forums. It would idle at 30-40W and at load 70-80W. So, I think the only problem would be the 65ºC as well as the previous point.

> Input current should not exceed 8A. For current higher load, we suggest ussing a 2x2 mini-FIT JR as an input connector

I have buyed this picoPSU pack. It has a mini-FIT JR, so it wouldn't be a problem

> peak load for individual rails should not exceed 60 seconds

> for long life operation, PSU temperature should not exceed 65ºC

Well, as all this points says + the specification of the +12V rail: max load 8A, peak load 10A. On MiniBox, they hadn't 150+110 power brick (out of stock), and I haven't found any pack at the best price, so I buyed this kit, although I think I will not draw more than 8A (8Ax12V= 96W)

I assume that your power brick has the mini-FIT JR connector, so probably your problems are:

1) If 110W are drawn, 110W/12V = 9.16A!! It is said "peak load for individual rails should not exceed 60 seconds"
2) Combined and sustained output should not exceed 65%, well.... :wink:
3) Probably the temperature of the picoPSU is around 60-65ºC, have you measured it?

So, why have you put a picoPSU system to your Pc instead of a microATX PSU or an ATX PSU form factor around 250-300W (250x0,7 = 175W, by this way your PSU live will be increased I think)?

About efficiency as Mike C says on this article, it comes from the power brick, so I don't know really how a picoPSU with a standar power brick could be more/less efficient than an 80+ ATX-PSU. Sorry

Hope to have been helpfull :)
[size=75][url=http://two.xthost.info/javitxi/CajaPc/cableadoV4/]My computer:[/url] Thermaltake Armor Jr +2S-Flex 1200rpm, Corsair VX450W, Asus P5Q-E, Intel e8500 + Noctua NH-C12P (actually without fan due to tests), RAM GeIL 4 GB DDR2-800, Asus EAH4850/HTDI (actually at warranty :() Future HTPC upcoming![/size]

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