Do active PFC power supplies run off high voltage DC?

[tom66]

I've got an idea for a project which needs +12V at around 30A from a high voltage 140 - 250V DC input (wide range.)

An active PFC computer power supply of decent quality should be able to work from this right? As all it is doing is boosting the rectified DC to around 400V. I will want to add some better input decoupling, although I'm not sure how critical it will be.

I'm also looking for reliability, so will probably be using some older server power supplies, with a dual redundant configuration.

[PeteS in CA]

Re: Do active PFC power supplies run off high voltage DC?

I've got an idea for a project which needs +12V at around 30A from a high voltage 140 - 250V DC input (wide range.)

An active PFC computer power supply of decent quality should be able to work from this right? As all it is doing is boosting the rectified DC to around 400V. I will want to add some better input decoupling, although I'm not sure how critical it will be.

I have some doubts about that. While it is true that a PFC circuit boosts the rectified voltage to ~400V, it does so in a way that the input current to the circuit is sinusoidal and follows the sinusoidal AC input voltage. The input voltage to the PFC circuit itself is unfiltered full-wave-rectified AC. What it would do with a DC input voltage, I'm not sure.

OTOH, you could have a DC input voltage applied to a non-PFC P/S, and it would work, but the problem for you would be the 140VDC low line.

[tom66]

Re: Do active PFC power supplies run off high voltage DC?

I have some doubts about that. While it is true that a PFC circuit boosts the rectified voltage to ~400V, it does so in a way that the input current to the circuit is sinusoidal and follows the sinusoidal AC input voltage. The input voltage to the PFC circuit itself is unfiltered full-wave-rectified AC. What it would do with a DC input voltage, I'm not sure.

OTOH, you could have a DC input voltage applied to a non-PFC P/S, and it would work, but the problem for you would be the 140VDC low line.

I think this is something that needs to be tested in the most dangerous way possible: with a bridge rectifier, a large cap, mains power and a variac. I'll leave it to another day when I'm more comfortable working around that sort of high voltage since it would have no regret at all in killing me if I made a mistake.

Maybe I'll just mod an active PFC power supply by installing a large 400V cap near the bridge rectifier input so it *thinks* it's getting DC input but it's actually getting AC.

[Per Hansson]

Re: Do active PFC power supplies run off high voltage DC?

It would work with a non PFC PSU, see this for example
http://www.youtube.com/watch?v=Nf2SK-79ecA

I don't think it would work with a APFC PSU since it tries to appear as a perfect sinusoidal wave to the supplying side.
So if you where to supply it with a flat DC voltage I think it would actually blow the PFC stage, you could try it with a cheap powersupply if you want more than my opinion.
But please do film it

[tom66]

Re: Do active PFC power supplies run off high voltage DC?

It would work with a non PFC PSU, see this for example
http://www.youtube.com/watch?v=Nf2SK-79ecA

I don't think it would work with a APFC PSU since it tries to appear as a perfect sinusoidal wave to the supplying side.
So if you where to supply it with a flat DC voltage I think it would actually blow the PFC stage, you could try it with a cheap powersupply if you want more than my opinion.
But please do film it

AD: Broken power supplies wanted!

I should get one of those s*** Atrix power supplies my brother insists on using because Maplin sell them cheap. £35 for a 650W! Yeah right. Saw a review showing 60% efficiency at 350W... there is no way in hell it will ever do 650W without blowing up. Full of CapXon too, bulging after 6 months. But it could be fun to try it on DC .

I predict that it will either: a) work perfectly (as it tries to maintain current as the input always looks near peak) or b) shut down/not work. I don't think it will blow up, but there's a first time to try everything.

To be investigated...