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How does a 450 Watt PSU attain 53 amps (636 watts) on the +12v rail

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March 18, 2013 10:27:45 AM

http://www.aria.co.uk/Products/Components/Power+Supplie...

Part number -
450W XFX Pro Core Edition 80PLUS Bronze Power Supply [P1-450S-X2B9]

- 550W of continuous power at 50°C
- Tight voltage regulation (±5%)
- High efficiency operation up to 85% (80 Plus Bronze)
- Single, high power +12V rail (up to 53A/636W)
- High quality Japanese brand capacitors (105°C)
- Quiet 135mm ball bearing fan provides superior cooling
- Supports multiple high-end graphic adapters (NVIDIA SLI & ATI CrossFire Ready)
- Supports the latest ATX12V and EPS12V standards
- Active PFC with Universal AC input
- Energy Star 4.0 and RoHS compliant
- 5-Year Limited Warranty

And what does the 85% (80 plus bronze) actually refer to?
March 18, 2013 11:10:51 AM

@ColGeek - thanks for the link, Oerclockers site also reported the same 53 amps (636 watts) but they stated a continuous output of 450 watts.

I've read reports where online resellers are overstating the facts to sell their wares, maybe this is just an example of many thousands listed and lots of Questions in the Power Supply Units Category to come .. lol

I'm still not familiar with the 80 plus Bronze if someone can enlighten me. Some people say it is 80% continuous power of the total peak power, others say other things so it would be good to get the real facts - If the total output (peak) power is 600 watts then the 80 plus % would equate to an actual continuous power of 480 watts, being the combination of watts for all of the rails, not just the 12 v rail.
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March 18, 2013 12:16:28 PM

@Colgeek - thanks for the link.

As stated in the Wiki, for 80% efficiency rating, a 600 watt PSU will draw 750 watts (WHAT?!!) from the power point and waste 150 watts (WHAT??) giving you your 600 watts power for the PC.

It really doesn't make sense to me that a 600 watt power supply would draw 750 watts from the mains power, what does a non-efficiency rating 600 watt PSU draw from the mains power? Assumedly 230 v 10 amp DC power equates to 2300 watts? Noo!!Yes??

"a 600-watt power supply with 60% efficiency running at full load would draw 1000 W from the mains and would therefore waste 400 W as heat. On the other hand a 600-watt power supply with 80% efficiency running at full load would draw 750 W from the mains and would therefore waste only 150 W as heat."

I'm a bit hesitant on posting this reply...
January 23, 2014 3:56:50 PM

Yet that's the way it works. For instance if I take my Watts Up Pro watt meter and plug my 3570k with a GTX 670 in to it then it reads that the machine is pulling about 310 watts from the wall. I know I have an 80Plus Bronze supply so it's somewhere near 85% efficient. That means 85% of that 310 watts is actually being converted to DC voltage at current the computer uses. This means my machine is actually consuming about 264 watts, the other 46 watts are lost to heat during the conversion from AC to DC in the supply.
January 23, 2014 5:36:29 PM

TenPc said:
http://www.aria.co.uk/Products/Components/Power+Supplie...

Part number -
450W XFX Pro Core Edition 80PLUS Bronze Power Supply [P1-450S-X2B9]

- 550W of continuous power at 50°C
- Tight voltage regulation (±5%)
- High efficiency operation up to 85% (80 Plus Bronze)
- Single, high power +12V rail (up to 53A/636W)
- High quality Japanese brand capacitors (105°C)
- Quiet 135mm ball bearing fan provides superior cooling
- Supports multiple high-end graphic adapters (NVIDIA SLI & ATI CrossFire Ready)
- Supports the latest ATX12V and EPS12V standards
- Active PFC with Universal AC input
- Energy Star 4.0 and RoHS compliant
- 5-Year Limited Warranty

And what does the 85% (80 plus bronze) actually refer to?


To answer the very simple part of this question re. 53A/636W: The 450 watt is the maximum continuous power the unit will supply. Every PSU should be capable of delivering for a very short time a maximum amount of power and that would be what the 53A/636W is referring to. Such a power increase might occur at start up. The power supply is NOT a 636 watt unit nor can it sustain that kind of output.
The other responses have covered the efficiency question really well.
January 23, 2014 5:49:07 PM

Max +12V1 Output Current (A) : 34
January 23, 2014 7:29:32 PM

TenPc said:
@Colgeek - thanks for the link.

As stated in the Wiki, for 80% efficiency rating, a 600 watt PSU will draw 750 watts (WHAT?!!) from the power point and waste 150 watts (WHAT??) giving you your 600 watts power for the PC.

It really doesn't make sense to me that a 600 watt power supply would draw 750 watts from the mains power, what does a non-efficiency rating 600 watt PSU draw from the mains power? Assumedly 230 v 10 amp DC power equates to 2300 watts? Noo!!Yes??

"a 600-watt power supply with 60% efficiency running at full load would draw 1000 W from the mains and would therefore waste 400 W as heat. On the other hand a 600-watt power supply with 80% efficiency running at full load would draw 750 W from the mains and would therefore waste only 150 W as heat."

I'm a bit hesitant on posting this reply...


Lets take this one bit at a time. Efficiency is how well a PSU converts the AC power from the wall into DC power for the PC. If you are drawing 1000W of power, and you are only 80% efficient at turning it into your desired output you will only have 800W of your desired output(1000*0.8=800). This also works the other way, if you need to provide 600W but you are only 80% efficient at converting the power you will need 750W(600/0.8=750). All power has to go somewhere, either into radiation(light), motion(motors), or heat. Since the PSU has no lights or motors all of the power it is using is being turned into the 150W of heat.

Most older PSUs which don't have an 80+ certification on them are only about 70-75% efficient, a 600W PSU that is 70% efficient will draw a bit over 850W at full load, giving off 250W of heat.

As for the 230V 10A part, yes that does turn into 2300W. Power= Volts * Current therefore 230V*10A=2300W. A PSU however takes the 230V AC from the wall and turns it into DC power at 3.3V, 5V, and 12V.
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