How does Active PFC Vs Passive PFC affect performance

[dssence]

Hi guys just wondering if there's such a big difference on PSU's which are PFC passive or active ones, and how does it effect performance.
Thanks

[Daijoubu]

Re: How does Active PFC Vs Passive PFC affect performance

It doesn't, nor is it more efficient (less actually), it's good from the point of view of your electricity company if I understand correctly

[Per Hansson]

Re: How does Active PFC Vs Passive PFC affect performance

Here is an excellent writeup for the end-users point of view...

http://www.dansdata.com/gz028.htm

[Galvanized]

Re: How does Active PFC Vs Passive PFC affect performance

Active PFC is requiored in the EU, here in The States it is not.

Generally but not always the better PSUs will have aPFC.
The biggest advantage of active for the home user is extended UPS battery run time. Don't ask me how but I have read it and EEs state it is so.
Active PFC does produce heat within the PSU, might be as little as ten watts of waste.
If one does not use a UPS or the UPS one uses does not have AVR(automatic voltage regulation), aPFC will condition input voltage from about 90VAC to about 140VAC. I think this helps stabilize output voltage. Please jump on me if I'm wrong.

Another good link http://www.techarp.com/showarticle.aspx?artno=81&pgno=0
Be sure to note Adrian's most excellent BIOS guide.

[willawake]

Re: How does Active PFC Vs Passive PFC affect performance

Active PFC is requiored in the EU, here in The States it is not.

PFC is required not active

[PeteS in CA]

Re: How does Active PFC Vs Passive PFC affect performance

IIRC, the EU doesn't explicitly require PFC, it just specifies the permitted magnitude of line voltage harmonic currents. PFC, active or passive, is necessary to comply,

Passive PFC is simpler - a 50Hz/60Hz inductor is added - but the inductor adds more weight than does active PFC. Active is more complex, but the current waveform is closer to sinusoidal and you don't need an input voltage range switch (or separate models for 115VAC and 230VAC).

[dssence]

Re: How does Active PFC Vs Passive PFC affect performance

Pete's you're telling this moves the waveform closer to sinusoidal how does this affect actually the cpu performance, like for instance I've read some car inverters 12volts to say 110 use sinusoidal quadrature kind of modulation does this add some kind of harmonics interference to the circuit? . What kind of inductors are used on this kind of PFC's.
Something else aside from the thread, somehow by googling on a review for the new mobo I bought I came accross with a link which had a review and built steps for an in parallalel circuit filter with lot's of caps in some sort of array, like the PSU plugged through it and then it came out another 24 pin plug which plugged onto the mobo.
I read some oscilloscope results saying this might reduce rippling on certain dc voltages , but question is , does this really affect up to what extent? performance wise
Thanks.

[PeteS in CA]

Re: How does Active PFC Vs Passive PFC affect performance

With a good P/S, case and MB, the type of PFC or lack thereof should be transparent in the performance of the computer. The advantage of PFC is in what it doesn't do to the AC line voltage (flat-top it in extreme cases) building wiring (heat up the neutral wires) and the utility's power lines, plants and transformers (which would have to be sized to handle high current spikes at the crest of the voltage sine wave.

[starfury1]

Re: How does Active PFC Vs Passive PFC affect performance

without getting into the semantics of Power Factor Correction.
There are others here that are far more qualified to answer that then I, and some have done so already

SMPSU are dirty beasts as far as the power grid is concerned

So governments have now forced the manufactures of SMPSU to clean up there act for the power grid.

just about most things that use a PSU now have the Switch Mode type in them so the problem of the nasties they create are much greater then they use to be.

So to a consumer there is little and in fact in some cases maybe of disadvantage in the use of PFC.

As far as a PFC in a computer PSU goes...not much advantage really

The catch is that it costs money to put it in so manufactures only recourse is to play up some slight advantage it might be to you for your computer.

To get you to buy one cause now it costs a little more to build them.

I have noticed they tend to push "reduce your power bill angle"...which if I remember right , you only pay for real power not apparent power losses anyway...so thats really some what of a lie...

To answer your question, little advantage really .....if any in real terms

To the power grid with zillions of these supplies hanging of it...big advantage

Active would be better then passive.
Of course an active one is more complicated and there is more chance for failure,
passive is simpler

So PFC is good for the environment as far as the power grid is concerned.

If you want to get in to it further
search out..... real power.... apparent power.... power factor correction.

just as an example

A fluro light has an inductor in it
now a one fluro here and there in houses isn't so much a problem
but look at you typical office building
its full of them...
so the each light must have a PFC cap put in it.

what happens is the inductor will cause a phase shift between the voltage and the current, so a capacitor will shift it back so they are more in sync.

it does get a bit more complicated (as pointed out above)
but thats the crux of it and putting it simply

There was another post on this somewhere on the forum too.

As PeteS said transparent

A well designed PSU isn't going to care whats happening on the mains side, So long as its DC reservoir Cap is full or near full it will just keep motoring along and regulating as well as it was designed to do


Hope it helps

Cheers

[PeteS in CA]

Re: How does Active PFC Vs Passive PFC affect performance

Linear P/Ss aren't cleaner when it comes power line harmonics than SMPSs. That issue is due to the large lytic caps after the bridge rectifier which only draw charging current just before and at the peaks of the voltage sine wave. While linear P/Ss have a 50Hz/60Hz transformer between the mains and the bridge rectifier, the transformer doesn't prevent the peak charging problem. Both Linear P/Ss and SMPSs have the regulator after the rectifier-filter stage.

Other than really early personal computers (e.g. the original TRS-80) and game consoles, basically all the PCs, Macs and game consoles that have proliferated over the past nearly 30 years have had SMPSs. Linear P/Ss are really low efficiency and heavy: the weight kept them out of PCs; the inefficiency will lead to linears going away due to Energy Star, Blue Angel, etc..