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PC Power Supply Discussion Troubleshooting and discussion of computer power supplies

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Old 05-05-2016
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Default Hold-up time explained

Yeah another topic about the hold-up time. Why? Because I got the feeling some really don't understand what it is, what it does and what the problem is.

What is the hold-up time?
It's the time in milliseconds that the PSU can work without without getting any power, measured at full load.

How does it work?
The primary capacitor of the PSU can store enough energy for the PSU to work some milliseconds after the power is cut.

How long should it last?
According to the ATX specification the PSU should deliver at least 17ms full power with voltages still inside the ATX spec.

But at least 1ms before the output voltages of the PSU go out of spec the PSU should drop the Power OK signal.

Power OK signal?
Yes Power OK signal, that's a wire in the 24 pins ATX connector that tells the motherboard that the power of the PSU is stable and that the PC can start or should shutdown.

What's the problem then?
Some PSU don't drop the Power OK before the output voltages of the PSU go out of spec. This isn't good because it puts a lot of stress on the components of the PC that are powered by the PSU and now getting voltages that are outside of spec.

Is it really a problem?
Well that depends if you experience a lot of problems with power outage where you life, it could be a problem. But if that is the case a UPS is maybe something that you should buy.

But there is something else you should know!
Hold-up time is measured at full load! Almost no one loads his of her PSU till full load. And even if someone does, the chance that PSU is working at full load if the power fails, is almost zero.

So that means that hold-up time actually should last a lot longer in real life conditions. It even could mean that the power OK signal drops before the output voltages go out of spec.

So it actually isn't a problem?
For most people not no.

So please don't make this a huge problem, because it isn't one. It simply isn't done right according to the ATX specification.

For more information and tests see the reviews from Aris on TechPowerUp and TomsHardware:
http://www.techpowerup.com/reviews/?...=25&order=date
http://www.tomshardware.com/articles...power-supplies

Last edited by -The_Mask-; 05-05-2016 at 06:17 AM.
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Old 05-05-2016
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Great and straight to the point info, I looked for something like this a few days ago but couldn´t find much
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Old 05-05-2016
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Your PG stuff is wrong. Will explain tomorrow.
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Old 05-05-2016
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Here in Germany hold up time is only relevant for professional use. I don't remember any power loss in the last two years here in my flat. In other countries power losses are normal. In my 6 month in spain the power was out at least once per month.
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Old 05-05-2016
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Quote:
Originally Posted by -The_Mask- View Post
.
.
.
So that means that hold-up time actually could last a lot longer in real life conditions. It even could mean that the power OK signal drops before the output voltages go out of spec.
The magic word is "could".
"Could" doesn't specify certainty. "Could" means that either it will or it will not !!
And as i said multiple times in the past, i'm not a person that likes risks, and the 50%-50% chance of the "could" word, is a serious risk percentage in my opinion.
So, if it 1) "could mean that the power OK signal drops before the output voltages go out of spec.", it also 2) could mean that the Power_OK could drop much much later after the voltages get out of spec!!!
So the conclusion is that we need even more thorough testing and NOT to abandon them completely and pretend that the issue doesn't exist at all !!!
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Quote:
Originally Posted by sith'ari View Post
The magic word is "could".
Changed the first could to should.

Quote:
and the 50%-50% chance of the "could" word, is a serious risk percentage in my opinion.
As I was trying to explain, the chance is probably very small in real life.
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Old 05-05-2016
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Quote:
Originally Posted by -The_Mask- View Post
Some PSU don't drop the Power OK before the output voltages of the PSU go out of spec.
And why then UVP doesn't kick in, in that case? Is it too slow?


Quote:
Originally Posted by Philipus II View Post
In other countries power losses are normal. In my 6 month in spain the power was out at least once per month.
Italy is much more similar to Spain.
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Quote:
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And why then UVP doesn't kick in, in that case? Is it too slow?
UVP is mostly set to kick in by a much bigger drop.
Quote:
Italy is much more similar to Spain.
The Netherlands is more like Germany, it almost never happens.
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Old 05-05-2016
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Quote:
Originally Posted by -The_Mask- View Post
Changed the first could to should.
As I was trying to explain, the chance is probably very small in real life.
Oh come on.....!!!
I can't resist with what you are writing!!! Again, probably doesn't specify certainty, and i'm not a person that likes risks and ....blah blah blah you know the rest !!!
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Quote:
Originally Posted by -The_Mask- View Post
UVP is mostly set to kick in by a much bigger drop.
1.2V are not enough? So which is the (general) UVP usefulness/goal?


Quote:
Originally Posted by -The_Mask- View Post
The Netherlands is more like Germany, it almost never happens.
Pares cum paribus facillime congregantur.
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