Active PFCs and UPCs - should I get rid of my power supply?

[AndyD2k]

So I've been reading online that mixing a UPS and Active PFC is not a good idea because of the simulated sines that are used in lower end UPSs. Because I don't want to spend $500 on an UPS, I was thinking whether it would make sense to look into switching out my PSU. The only thing is that I'm not sure whether the best PSUs all have Active PFC as a feature.

Do they?

I really do want to add a UPS though. I had a short go through my apartment a few weeks back and while I have fairly expensive power strips it did nothing to stop a device from getting fried. That was just $40 but I don't want the same thing to happen to my PC

 

[HOOfan 1]

Yes, the best PSUs have active PFC. That isn't to say PSUs that don't have APFC are crap...but the BEST will have APFC. There is a pretty much unresolved debate about simulated sine wave and APFC...but you can find true sine wave UPS for less than $500.

http://store.opti-ups.com/Product/Item.aspx?id=184

 

[AndyD2k]

I keep thinking UPCs I'll give that a look thanks

 

[AdamK47]

I'm in the same boat as you. From about an hours worth of Google searches it appears that if you have a PFC power supply and a simulated sine wave UPS that is not constant on (only switches to battery when AC power is lost) then you should be good to run for several minutes and power off when running off of the battery. It appears as though the problems with this combo occur if you use it for extended periods of time.

 

[HOOfan 1]

It is only Active PFC that you would have to worry about anyway. If the PSU doesn't have the red voltage selection switch, then it has APFC.

Most UPS switch to battery only when the AC mains has been cut. The online units which constantly run off battery are VERY expensive.

 

[Yellowbeard]

If I was forced to choose between having a quality PSU OR a questionable PSU with no active PFC in tandem with a UPS, I'd ditch the UPS.

Unless you existing UPS is making your PSU buzz, you should be fine to keep using it.

 

[AdamK47]

OK, after some research I found out why a simulated sine wave is bad for a PFC power supply. Someone on another forum contacted Silverstone and here is his response (obviously not from an English speaking country):

http://www.jonnyguru.com/forums/showthread.php?t=3964

This is the same situation for all of PSU even not SilverStone.
We do have experience on the UPS damage PSU, and my explanation is as follow.
The problem is cause of UPS sent square wave to PSU when AC loss then Bridge diode inside of PSU will convert square wave into PSU primary circuit.
Therefore, the voltage cross on bulk capacitor will be near to Top of UPS square wave in continuously.
For example, voltage on the top of square wave is 470V then PSU bulk capacitor cross voltage is near 470V.
The 470V will damage PSU bulk capacitor or other components in primary circuit since the rating of bulk capacitor is 200V * 2 pcs = 400V.
One kind of UPS is send sine wave to PSU when AC loss that won’t get this issue but the price is higher.
Actually, there is not chance to solve this issue by PSU due to too many components must be upgrade.
But UPS just need to extend PWM duty cycle that top voltage of square wave can be reduced under 400V.
It is easiest way to resolve this issue.

His response to the question if a 120V source is used:

It is fine if you living in US and used 120V input in your OP700, even by a not pure sineware UPS.

It is so difficulties to clear this responsibility between UPS and PSU of UPS not support sineware outputs will damage PSU when input 240V.
Even a UPS mainstream company like APC, that products will not all support sineware.
Anyway, there is not chance to solve this issue by PSU due to too many components must be upgrade.
But UPS just need to extend PWM duty cycle that top voltage of square wave can be reduced under 400V.
It is easiest way to resolve this issue.

1) If your PSU input voltage = 120V is FINE to work, if your PSU input voltage = 230V will damage PSU IMMEDIATELY.
2) PSU is not design for NON sineware input, it is not health.
Just like smoke is not health for people, but if smoking, people will NOT dead IMMEDIATELY.
If your city isn’t power cut every day and every hours, that damage for you is very small.
3) This is the same situation for all of PSU even not SilverStone.

It looks like if you live in a country with 120V power you are fine as long as the PSU doesn't run on it at extended length. A country with a 220V system has a good chance of killing the PSU when using a simulated sine wave UPS since the square wave has a peak of up to 470V.

 

[SparkyJJO]

If I was forced to choose between having a quality PSU OR a questionable PSU with no active PFC in tandem with a UPS, I'd ditch the UPS.

Unless you existing UPS is making your PSU buzz, you should be fine to keep using it.

Hmm.. my HX620 does buzz when on battery :hmm: But then, so did my old non-PFC Antec PSU that I had prior to the Corsair unit, so I never gave it much thought :|

 

[AdamK47]

In the same thread I posted above it mentions buzzing with some PSUs. They say it's fine and won't damage anything. The buzzing is a result of the simulated sine wave.

I tried my computer on the UPS I have in battery mode for about 10 minutes last night. There wasn't any buzzing or anything else out of the ordinary.

 

[PsiStar]

This kind of buzzing *was* typically 3rd harmonic energy (180 Hz) and the actual sound came from power transformer laminate vibrations == benign. Current PSU design is different & the buzzing could be PFC related or switching circuit related. Although switching circuits are typically so high in frequency that not even the dog will here it.

AndyD2k ... you didn't say too much about the "... short go through my apartment ...". Was this from a nearby lightning strike? Trying to keep in the context that you describe it, it sounds as if there was a power surge or an over voltage due to lightning.

If that was the case, most MOV protected devices may lose the protection ... MOVs will fail eventually in other words. I don't know how to know without actual visual examination of a MOV if it is ok or not. That would require opening up the strip. Unless you are comfortable with electricity, I wouldn't. Although I would suggest that you relace the strip that had the device that failed plugged into it. Definitely if you live in an area prone to frequent t'storms.

Last, you do bring up a good question about the quality of UPS output & how it affects the newer PFC enabled PSUs. This will take some research, so don't hold your breath (here). There are quality systems on both end of that power cord and some ... lets say less than quality.

 

[AndyD2k]

Hey man. Roommate was doing something in the apartment and sparked something in one of the outlets. Like a mini fire. When I got home all my devices were off and my HDMI switch that was drawing power from a Tripp Lite surge protector was fried

I don't think a UPS will prevent this but would at least let my devices gracefully shut down when I do lose power. The incident just reminded me that I had to look into it

 

[dman]

Interesting read. Since I'm on US / 110 I guess it's a non-issue, but, still interesting.