Antec PSU retaining power after shutdown?

[MrUniq]

I've had a pretty good run with power supplies and I've never had them fail on me. I already have a TP2 and I was satisfied with it...I just picked up at SmartPower 2 today for my secondary PC. I have an Asrock Sata 939 motherboard. Strange thing I've never seen before though. After I shut down the power and unplug the power cord....when I plug it back in the fans inside the case temporarily spin for about 1 second. It also happens when I simply shut down, flip the switch in the back to 'off'...and then switch it to 'on' again. It seems like the PSU doesn't dissipate all of it's power when it shuts down. I'm not real savy when it comes to terminology..I just use 'common sense' when I set up the wiring. I only have one HD and 2 DVD drives running currently. AMD64 3200+ ... I'm not an OC'er either. Anyone have any ideas or is this somewhat normal behavior for the SmartPower?

 

[dBTelos]

Thats normal of most PSUs IIRC. Not allllll of the power goes away when you shut down, some power is left in the PSU parts, which then can come back in some cases.

 

[MrUniq]

I see whew..I was baffled there for a moment. Thanks.

 

[Zepper]

If you have a load on the PSU like a mobo or some drives or something there should be very little if any charge left as it will bleed off thru the load. If you powered it up without a load, the charge could remain for a long time. It's a good idea NOT to run a switching PSU without a load.

.bh.

 

[Navid]

Originally posted by: MrUniq
I've had a pretty good run with power supplies and I've never had them fail on me. I already have a TP2 and I was satisfied with it...I just picked up at SmartPower 2 today for my secondary PC. I have an Asrock Sata 939 motherboard. Strange thing I've never seen before though. After I shut down the power and unplug the power cord....when I plug it back in the fans inside the case temporarily spin for about 1 second. It also happens when I simply shut down, flip the switch in the back to 'off'...and then switch it to 'on' again. It seems like the PSU doesn't dissipate all of it's power when it shuts down. I'm not real savy when it comes to terminology..I just use 'common sense' when I set up the wiring. I only have one HD and 2 DVD drives running currently. AMD64 3200+ ... I'm not an OC'er either. Anyone have any ideas or is this somewhat normal behavior for the SmartPower?

I don't think this is the PSU doing anything! I think it is the motherboard! You know the power switch (in front on the case) is directly connected to the motherboard. When you flip the switch at the back of the PSU on, as long as you have not pressed the power switch in front, no power should be transferred to any component on the motherboard.

But, I have the same motherboard and the exact same thing happens with Seasonic S12-500W and Ultra X-Finity 500W.

 

[Comdrpopnfresh]

I have the smartpower as well. I notice when i flick the switch ont he PSU and hit the power button on the front of my case fast enough I can start my computer- horribel for the harddrive I imagine. also- whether is my case nto dissapating the heat well enough or not, but if I go to bed right after playing games, when I wake up the next day the top of ym case above the psu is warm- I've never experience that before, then again never had >350watts before.....

 

[JimPhelpsMI]

Hi, Some PSUs do that. It's residual voltage still stored in the Filter Capacitors. It bleeds off in a few seconds.

Jim

 

[Navid]

You turn off the PC through the Start menu in Windows. The PC shuts down.
Now, you flip the switch at the back of the PSU off. Now power is completely disconnected from the motherboard. After a few minutes, you flip the switch at the back of the PSU on. The fans spin for a second. Flip the switch back off and on again. The fans spin again. You can do this as many times as you want without ever turning on the PC. If it was charge storage, it would not keep going on and on.

 

[JimPhelpsMI]

Hi Navid, How many PSUs have you repaired?

 

[imported_Imp]

Originally posted by: Comdrpopnfresh
I have the smartpower as well. I notice when i flick the switch ont he PSU and hit the power button on the front of my case fast enough I can start my computer- horribel for the harddrive I imagine. also- whether is my case nto dissapating the heat well enough or not, but if I go to bed right after playing games, when I wake up the next day the top of ym case above the psu is warm- I've never experience that before, then again never had >350watts before.....

I've also noticed the warm case above the Smartpower even when my machine has been off for hours/days. Nothings broken yet, but it just bothers me that it's wasting so much juice acting as some kind of half-assed radiator.

 

[L00ker]

This is perfectly normal as it initially powers up then determines it is supposed to be in a powered down state and goes back into that state as far as storing power (i.e. the delay between when you switch off the PS and when the light on the mobo goes off) this is due to the capacitors on both the motherboad and the power supply

 

[Navid]

Originally posted by: JimPhelpsMI
Hi Navid, How many PSUs have you repaired?

In response to your question, I design electronics. I do not repair PSUs.
However, this is not a PSU issue. It is a motherboard issue.

 

[MrUniq]

I think so too...with the Asrock I noticed it has no LED's..unlike my Asus Mb's. The led on those always go off after about 5 secs after powerdown.

 

[L00ker]

If you really think it is an issue at all then you are mistaken x1 if you think this is a motherboard issue then you are mistaken x2 and furthermore if you "design electronics" then you should be more than aware of the concept of capacitance discharge and the concept of exponential decay, this relates to how the psu has residual power that powers the motherboard for a short period of time after the power to the supply is cut off. As for the initial spinup this is controlled by the logic circuitry internal to the supply and again is perfectly normal

 

[Navid]

We may be talking about different things.

This happens with three different power supplies that I have tried and a forth one that the OP has tried. The only common thing between our systems is our motherboard.

The same power supplies did not cause this with an ASUS P4 motherboard.

If the switch was at the output of the power supply and you opened the switch and then closed it and there was this short fan spin-up, it could be charge storage inside the PSU.

However, the switch we are talking about is at the back of the PSU, which only disconnects the PSU from the AC line only when opened but leaves the power supply connected to the motherboard.

So you say this is some charge stored in the PSU. OK, let's say that is the case. Now, we close the switch at the back of the PSU and the fans spin for a second. Is the PSU not discharged now? Why is it that if we do not turn on the PC and open the switch at the back and close it again, the fans spin again for another second? Why is it that this can be repeated over and over again without ever turning on the PC? Considering that the PC is never turned on, where is the charge coming from?

I welcome your and everyone else's opinion and do not care what you do. I appreciate it if you extend the same courtesy towards me. I never bragged or claimed that I was an expert in anything. I only posted my opinion. Unfortunately, a personal question was asked from me. Even though, I thought that question was out of line, I answered it since I have nothing to hide. But, I prefer to keep these forums focused on the technical subjects rather than personal.
If I do not know something, that is fine; I learn new things every day. That is why I come to these forums, to learn. And I thank you for your help.

 

[L00ker]

Originally posted by: Navid
We may be talking about different things.
<snipped...>
However, the switch we are talking about is at the back of the PSU, which only disconnects the PSU from the AC line only when opened but leaves the power supply connected to the motherboard.

Right I understand which switch you are referring to, in any case that switch connects/disconnects the power supply from the wall in a simplistic way.

Originally posted by: Navid
So you say this is some charge stored in the PSU. OK, let's say that is the case. Now, we close the switch at the back of the PSU and the fans spin for a second. Is the PSU not discharged now? Why is it that if we do not turn on the PC and open the switch at the back and close it again, the fans spin again for another second? Why is it that this can be repeated over and over again without ever turning on the PC? Considering that the PC is never turned on, where is the charge coming from?

No the initial spin up of the fans (upon initial turn on of the power supply and subsequent turn-offs and ons) is the power supply doing a sort of post (only comparison I can think of) to ensure it is functioning correctly which on a pretty simplistic level consists of powering up the circuit charging the capacitors and ensuring all components (fans other ic's and such) are functioning then returns to the powered down state which provided you do not flip the switch again (in to an off or open state) will put it in a sort of standby mode. Then the fans etc will spin up again once you soft power it on. If you disconnect the power or flip the switch again it will remove power from the circuit and upon closing it will initiate this post again this is why it is generally repeatable over and over...

Originally posted by: Navid
I welcome your and everyone else's opinion and do not care what you do. I appreciate it if you extend the same courtesy towards me. I never bragged or claimed that I was an expert in anything.

Previous statement:

Originally posted by: Navid
In response to your question, I design electronics. I do not repair PSUs.

Based on this statement I had (and reasonably so) an expectation that you understood some of the more simple concepts of electronic design and operation to include some of the laws of capacitance, not requiring "expert" knowledge.

Originally posted by: Navid I only posted my opinion. Unfortunately, a personal question was asked from me. Even though, I thought that question was out of line, I answered it since I have nothing to hide. But, I prefer to keep these forums focused on the technical subjects rather than personal.
If I do not know something, that is fine; I learn new things every day. That is why I come to these forums, to learn. And I thank you for your help.

I didn't make any personal statements so I am not sure if you are attempting to say that I did, I merely claimed that you were mistaken on 2 points. If thats personal to you maybe you should re-evauate what a personal comment is...

 

[the Chase]

I have the same PSU and a chaintech motherboard (see sig) and awhile back the system would not want to power back up after shutting down the computer. It would give a half second "blip" of power and then nothing. Then I found out if I flip the switch in back of PSU off and back on the system starts up fine. I thought my motherboard was on the way out but after installing my older Antec truepower 430 the system starts fine all the time. Any ideas?

Sorry to slightly derail this, it seems somewhat related.

 

[Navid]

Originally posted by: L00ker
No the initial spin up of the fans (upon initial turn on of the power supply and subsequent turn-offs and ons) is the power supply doing a sort of post (only comparison I can think of) to ensure it is functioning correctly which on a pretty simplistic level consists of powering up the circuit charging the capacitors and ensuring all components (fans other ic's and such) are functioning then returns to the powered down state which provided you do not flip the switch again (in to an off or open state) will put it in a sort of standby mode.

I though the idea was that there was some charge stored in the PSU and the reason for the fan spinning for a moment was that charge and it was not intentional. Reading this section of your post, I believe you are implying that this is by design and meant to happen. Should it then not happen with all motherboards? Can you explain why some motherboards do not show this behavior with the same power supply? For example, P4P800 deluxe, which I used to have.

Is there any document that can provide more information about such phase, during which the PSU charges up the rails only for a moment and then discharges them back down?

This is a link to the power supply design guide from Intel.
http://www.formfactors.org/developer/sp...v%20power%20supply%20design%20guide%22

On page 25, it talks about different phases of operation. I cannot find anything about a temporary power up of the rails anywhere.

On page 27, it talks about the +5V standby output, which comes on as soon as the switch at the back is turned on while all the other rails are supposed to stay down!

When you say that the PSU momentarily powers up the rails, does that not also momentarily power up the hard drives? Is that good for a hard drive?

 

[L00ker]

Originally posted by: Navid
I though the idea was that there was some charge stored in the PSU and the reason for the fan spinning for a moment was that charge and it was not intentional.

Two different things here, yes there is a residual charge this is why (esp if you have an led on your motherboard) if you cut the power switch on the back the light doesn't go off immediately due to a built up charge in the caps.

The initial spinup is the PSU powering up (not necesarily powering the rails) checking it's logic and IC's then going into standby mode.

Originally posted by: Navid Reading this section of your post, I believe you are implying that this is by design and meant to happen. Should it then not happen with all motherboards? Can you explain why some motherboards do not show this behavior with the same power supply? For example, P4P800 deluxe, which I used to have.

Yes by design the power supply (in most cases) should briefly power up and then power down some spin the fans some don't (this would be unique to each manufacturer) It may happen with most motherboards but I don't see why it wouldn't on others

Originally posted by: NavidIs there any document that can provide more information about such phase, during which the PSU charges up the rails only for a moment and then discharges them back down?

Not rails necesarily (although some manufacturers may do this) just logic circuitry.

Originally posted by: NavidThis is a link to the power supply design guide from Intel.
http://www.formfactors.org/developer/sp...v%20power%20supply%20design%20guide%22

On page 25, it talks about different phases of operation. I cannot find anything about a temporary power up of the rails anywhere.

On page 27, it talks about the +5V standby output, which comes on as soon as the switch at the back is turned on while all the other rails are supposed to stay down!

When you say that the PSU momentarily powers up the rails, does that not also momentarily power up the hard drives? Is that good for a hard drive?

No when the power supply momentarily powers up it powers only itself as a matter of a self check (to speak of) not the peripherals presenting a load on it.

 

[MrUniq]

Hey guys interesting debate..I'm learning some things I didn't quite know about PSU's and why they would spin up after shutdown...

Chase that is what prompted my question in a way. I had a 2 year old Kingwin that wouldn't power up Asrock system...but only after I hit the power, then flipped the switch in the back off/on. That promted me to get the Antec Smartpower which solved that issue but I began to notice the short 'surge' when u plugged it back in.

 

[Navid]

Originally posted by: L00ker
No when the power supply momentarily powers up it powers only itself as a matter of a self check (to speak of) not the peripherals presenting a load on it.

But, if it does not power up the peripherals, how do the case fans spin? That is what this thread is all about!

The fans that spin momentarily are the case fans and the CPU fan. Those fans are powered by the 12V rail from the supply. There is either voltage on the 12V rail or not. The power supply cannot selectively power up some components like the fans and not the rest of the components like the hard drives.

Did you think we were talking about the PSU fan?

 

[L00ker]

I thought the reference was to the PSU fan, however aside from that the power supply can power itself up without putting power across the rails, this is not entirely uncommon, however the case fans and cpu fan spinning up is another story. How do we know for sure that it's the case and cpu fans spinning up? by sound? or is it visible? What power source are they connected to? the motherboard? or are they connected directly to the PSU, if they are connected to the motherboard (cpu fan should be) then I would agree that the motherboard is what is controlling those fans but if they are conected to the PSU I don't think they should power up upon initial connection of the PSU to power... So OP you are referring to the CPU fan and Case fan, are they both conneced to the mobo?

 

[Navid]

Only after reading your last post, I suspected that you may have thought we were referring to the PSU fan. I am glad the misunderstanding is resolved.

In my case, I can easily see my intake fan. Also, when the case is open, I can see all of the fans. Even the graphics card fan spins momentarily when the back switch is turned on.

Most fans use the 12V rail. In an ATX system, all the rails (12V included) other than the 5V standby rail are controlled by the motherboard (soft start-up). That is why you can power up a PSU by connecting the green wire on the motherboard 20 or 24-pin connector to the ground (black) wire. So, even if the fan is connected directly to the PSU, it is the motherboard that causes the momentary spin-up.


None of the case fans should spin until the power switch in front of the case is pressed.
But, they do. And that means that even the hard drives get power momentarily when the switch at the back is flipped on.
And that is the issue with the Asrock motherboard if I can now call it that!