Non-sinusoidal UPS+active PFC -> DC feed?

[Behemot]

Have anybody here tried feeding PSU with DC? According to theory, it should work without problems, found a few guys here and there mentioning who supposedly tried some types of SMPS on DC output.

The problem with older/todays cheaper UPSes is that their output has nothing in common with sine wave and PSUs with active boost PFC do not like that at all. But by just rectifying it (and maybe with some bulk capacitor) it should be just fine, no? The input filtering should not care and than there is rectifying bridge anyway. Only drawback from this is that only two diodes in the PSUs bridge would be conducting all the time, but they should handle the stress…

[tom66]

Re: Non-sinusoidal UPS+active PFC -> DC feed?

I don't see how this is any different to feeding a PSU with a square wave like most non-sine UPS already do. They have bridge rectifiers in them already.

[Behemot]

Re: Non-sinusoidal UPS+active PFC -> DC feed?

Don't think so. Many of them do "sine wave aproximation" what ends like this

That is an actual UPS (APC BackUPS 500 VA) with Seasonic S12-II. I have the feeling the X-Bit Labs do this testng with each PSU they review and most of them do not work together with such UPS properly. And their PSU has "iteration aproximation of sinus-wave" which should be "hunchbacked" sinus, not that stuff at this picture and still, some of them almost do not work at all.

[cheapie]

Re: Non-sinusoidal UPS+active PFC -> DC feed?

That is an actual UPS (APC BackUPS 500 VA) with Seasonic S12-II.

That's the exact setup that I have, and everything works fine.

[budm]

Re: Non-sinusoidal UPS+active PFC -> DC feed?

The PS can take the AC stepped-sine wave from UPS. But you are asking about feeding the PS with DC instead of AC (either pure sine wave or stepped sine wave)? It will not work if the PS uses voltage doubler circuit or if it has PFC Voltage booster circuit, and you do not need PFC if the power source is DC.

[Behemot]

Re: Non-sinusoidal UPS+active PFC -> DC feed?

The PS can take the AC stepped-sine wave from UPS. But you are asking about feeding the PS with DC instead of AC (either pure sine wave or stepped sine wave)? It will not work if the PS uses voltage doubler circuit or if it has PFC Voltage booster circuit, and you do not need PFC if the power source is DC.

I said active boost PFC, is there anything you don't understand on that? But I do not see why it should not work, the boost circuit already uses DC and nothing but DC: There is bridge rectifier in front of it. You need the PFC because primary side expects 380+ V from boost in there, not 325 V.

That's the exact setup that I have, and everything works fine.

What version and what PSU? They made like 10 of them. Just read through X-Bit labs reviews, most of the PSUs do not work over 300 watts.

Well, I guess I'll have to make my own testing than.

[budm]

Re: Non-sinusoidal UPS+active PFC -> DC feed?

If you look at the PFC booster circuits (it uses pulsing DC 100Hz Euro, 120Hz US, you will not see filter cap AFTER the bridge) you will see why feeding the steady DC and you will understand why it will not work, the filter cap is AFTER the PFC output, not after the main bridge rectifier, and also the Phase sensing circuits. Do some reading.

[Behemot]

Re: Non-sinusoidal UPS+active PFC -> DC feed?

I know very well where the capacitor is. Boosting is done through the PFC coil but in material I've read, nobody said it is charging because of rectified sine wave but more like because of switched charging (when transistor is on, coil charges and at the moment of transistor going off, it creates voltage spike, that's how I understand it anyway).

[cheapie]

Re: Non-sinusoidal UPS+active PFC -> DC feed?

What version and what PSU? They made like 10 of them. Just read through X-Bit labs reviews, most of the PSUs do not work over 300 watts.

Well, I guess I'll have to make my own testing than.

I don't think it's loaded that heavily. It's a Seasonic S12II Bronze 520W, and now that I looked closer, it appears that I actually have a 600VA (APC) UPS, not a 500VA.

[Kiriakos GR]

Re: Non-sinusoidal UPS+active PFC -> DC feed?

I have the feeling that at 120V (USA) there is no active PFC PSU.

[goontron]

Re: Non-sinusoidal UPS+active PFC -> DC feed?

i have seen a PSU run on batteries before http://www.youtube.com/watch?v=Nf2SK...eature=related

[Behemot]

Re: Non-sinusoidal UPS+active PFC -> DC feed?

I have the feeling that at 120V (USA) there is no active PFC PSU.

All of them are, if marked 90-250 V AC, than they are boosting rectified input to +-380 V DC.

i have seen a PSU run on batteries before http://www.youtube.com/watch?v=Nf2SK...eature=related

Unfortunatelly it is not helping much, that is some OEM Fortron, probably older one with passive PFC.

[goontron]

Re: Non-sinusoidal UPS+active PFC -> DC feed?

Unfortunatelly it is not helping much, that is some OEM Fortron, probably older one with passive PFC.

well here is a schematic for an newer 400 watt ATX12 PSU and i don't see anything before the mains rectifier...

[Behemot]

Re: Non-sinusoidal UPS+active PFC -> DC feed?

This is either no- or passive PFC PSU, it has voltage doubler.

[Behemot]

Re: Non-sinusoidal UPS+active PFC -> DC feed?

It works. Adapter for running active-PFC PSUs on these modified sine-wave UPSs is being developed ATM.