How important is PFC ?

[Serville]

What is this Power Factor Correction ?

How important is PFC? Even TH didn't even mention it in his PSU review. And most people do not seem to care too much about it either.

Some people say PFC gives more power than non-PFC unit, ex: a 400w non-PFC PSU gives effectively around 70% power or 280w , and Active-PFC unit can raise this bar to 98% or 390w.

Some others say PFC is only a feature that helps stabilize the voltage level under load. Which one is true ?

What does it mean when the manufacturers state that PFC has 98-99% power factor , but efficiency at 70% ?

Can someone clear this up for me once in for all ?

 

[Since87]

Power Factor Correction affects the way current is drawn from the wall outlet.

The AC voltage available at the wall outlet has the form of a sine wave.

A power factor corrected supply will draw draw current from the wall outlet that is, (at least nearly) also a sine wave and in phase with the voltage. The following image illustrates the difference between an in phase current and an out of phase current.

This kind of phase shift is more relevant for electric motors and other inductive loads. A non power factor corrected PSU, will usually draw spikes of current at the peaks of the voltage sinewave. (No picture handy.)

In both cases, (out of phase current, and spikes of current) the peak current draw is greater for a given amount of power consumption than with a power factor corrected load. One result of this, is that the electrical utility has greater expenses supplying electricity to a non power factor corrected load. Another issue is that circuit breakers may trip due to the high currents.

In addition, the spikes of current drawn by a non power factor corrected load can result in EMI and distortion of the incoming voltage sinewave. Other devices powered with a distorted line voltage may get excessively hot.

I believe that in most of Europe it is a requirement that anything using more than a certain amount of power, be power factor corrected.

Those issues aside, what difference does it make to the operation of a PSU?

Not much.

There's likely to be a small gain in the PSU's efficiency with well implemented power factor correction, but it won't, "give more power", or "stabilize the voltage under load."

Efficiency is the output power of the power supply divided by the input power to the powersupply. If a power supply is 70% efficient, and it has a 70 Watt load on its output, then it will be drawing 100 Watts from the wall outlet. The difference between input power and output power, (30 Watts in this case) is dissipated as heat in the PSU. High efficiency reduces your power bill, and the amount of waste heat.

I would recommend getting high efficiency, and power factor corrected supplies, but it won't improve your computer's operation in any meaningful way.

 

[Giblet Plus!]

I would recommend getting high efficiency, and power factor corrected supplies, but it won't improve your computer's operation in any meaningful way.

What about overclocking ability? I'm thinking of getting a new PSU, and the 400W Forton with PFC looks pretty good.

 

[ryuen]

ya same here. wish they had a 400w with 120mm

 

[ryuen]

also u said you pay less on your power bill. do you save like a lot? or like 2 dollars?

 

[R4z0r4mu5 Pr|m3]

hello, less heat in your case!

 

[Serville]

Thanks for the explanation.
I thought PFC would give more workhorse than a non-PFC.
In that case, I think I don't have to buy another PSU, because mine is non-PFC. It's HEC 400w LD-T

 

[Since87]

What about overclocking ability? I'm thinking of getting a new PSU, and the 400W Forton with PFC looks pretty good.

PFC won't have any effect on overclocking ability. It only effects the input of the supply. The output is a completely separate issue.

 

[hitechjb1]

Are PSU in the Antec True Power series PFC type? I can't find that in their spec.

 

[Since87]

also u said you pay less on your power bill. do you save like a lot? or like 2 dollars?

If the Power Factor Correction has a meaningful effect on power savings, it will be reflected in the supply's overall efficiency spec.

Comparing the Sparkle FSP400-60PFN and FSP400-60GN. (Couldn't find substantial Fortron data.)

The power factor corrected version is 68% efficient and the non power corrected version is 65% efficient.

Suppose you run your machine 24/7 with a continuous draw on the supply of 200 Watts:

Input power
PFC 294 Watts
Non-PFC 308 Watts

Total power saved 14 Watts. At $0.07 per kilowatt-hour that's about $8.60 a year. At Newegg, the price premium for the PFC version is $4, so it's paid for in six months.

There are a lot of other specs that make the PFC Sparkle substantially more attractive than the non-PFC Sparkle. There are other areas where the non-PFC has better specs, (negative rail ripple and noise) but I'd still go with the PFC version.

 

[Since87]

Are PSU in the Antec True Power series PFC type? I can't find that in their spec.

Quoting from the True Power user manual:

"Applicable only to models designed for sale in the European Union: TruePower models designed for the EU include Power Factor Correction (PFC) circuitry in accord with European standard regulation code EN61000-3-2. By altering the input current wave shape, PFC improves the power factor of the power supply and results in increased energy efficiency, reduced heat loss, prolonged life for power distribution and consumption equipment, and improved output voltage stability."

I don't like Antec, because their literature is more marketing BS than engineering criteria. This latest find does not impress me either.

 

[hitechjb1]

I looked at the user manual per your pointer, so the PFC is only for the EU countries, and probably NOT for this side of the Atlantic. If it has such advantages of

"Applicable only to models designed for sale in the European Union:
... PFC improves the power factor of the power supply and results in increased energy efficiency, reduced heat loss, prolonged life for power distribution and consumption equipment, and improved output voltage stability." (quote from True Power manual)

Why Antec has to make different models for the US and Europe, and maybe other countries, ... and some countries do not need better energy efficiency ????

Does that mean there are some advantages without PFC, otherwise why do they maintain more than one models w/ and wo/ PFC (means higher cost for them).

 

[Since87]

Does that mean there are some advantages without PFC, otherwise why do they maintain more than one models w/ and wo/ PFC (means higher cost for them).

Designing the circuit board so that it can be built with or without PFC is not hard.

Where you can get away with it, you leave out the PFC components and have a higher profit margin. If the money saved on parts didn't justify having two assembly processes, they wouldn't do it.

 

[hitechjb1]

Just for the sake of discussion:

1. So if one wants to have an Antec True Power PSU with PFC, one can order it from Europe w/ the correct part no. Should it be able to work here, of course, assuming setting the switch to 115 V instead of the 230 V default in EU.

2. Also in the manual w/ English, French, Spanish, so I interpret one manual for both US and Europe and many other parts of the world, ...

It claims power efficiency 68% (min) at full load, 115/230Vac 60Hz/50Hz.

What is that power efficiency of 68% refers to? For both 115V (imply US), 230V (EU and ...), and for both PFC and non-PFC ??

Maybe they have only one model w/ PFC, the statement about PFC may be just a legal thing for EU.

3. Is there a simple way to see whether a PSU is PFC enabled or not? Maybe a jumper or switch inside the PSU???

4. A 3% saving on PFC is a lot for a country with so many PSU's.

 

[Since87]

Another quote from the manual:

"Note (not applicable to models designed for the European Union): Check the red power supply voltage switch setting before installation. It should be the same as your local power voltage (115V for North America, Japan, etc. and 230V for Europe and many other countries). Change the voltage setting if necessary. Failure to take this precaution could result in damage to your equipment and could void your warranty."

As is typical for PFC supplies, the PFC version of the True Power will operate over a 90 to 265 Vac range without the need for switching. So, if you have an input voltage switch on the supply, then it is not the PFC version. Any Europeans out there who can confirm this?

I would expect the European version to work fine in the US.

What is that power efficiency of 68% refers to? For both 115V (imply US), 230V (EU and ...), and for both PFC and non-PFC ??

Good question. Not much detail there. I can't say for sure. They do say that 68% efficiency is minimum. Maybe the PFC versions have better than 68% efficiency? Dunno.

That 3% difference between the Sparkles may not be due to the PFC alone. It appears there are other differences.

In any case, the difference that PFC makes in the efficiency of the supply is only part of the picture. Another significant issue is the overcapacity that the electrical utilities must provide to cope with it. We all pay for non-PFC loads.

 

[star882]

Active PFC allows the B+ to be much higher than the peak of the AC line.
I have a 200w Delta PSU with 2 400v, 470uF caps.
There is a complex circuit that boosts the AC line to about 340v.

 

[josi]

Good question. Not much detail there. I can't say for sure. They do say that 68% efficiency is minimum. Maybe the PFC versions have better than 68% efficiency? Dunno.

According to the ATX/ATX12V Power Supply Design Guide, the power supply should be a minimum 68% efficient under maximum load at any rated AC input range.

That 3% difference between the Sparkles may not be due to the PFC alone. It appears there are other differences.

3% difference is typical for Passive-PFC power supplies (often realised via one large coil). Active-PFC should have 10-15% more efficiency.

 

[larrymoencurly]

According to this review of an Antec 550W with active PFC, the efficiency was measured to be 64-75%, depending on load. Isn't that about average for ATX PSUs?

There is a complex circuit that boosts the AC line to about 340v.

More than just a couple of diodes and filter capacitors? That's what all of mine have (no active PFC in any of them).

Who makes high efficiency (85% or more) ATX PSUs?

 

[Serville]

I think PFC is not as important as people think.
It seems only the EU has this requirement, but not the rest of the world. If it is important, then I believe it should have become a standard for ATX PSU, and should have been a feature included by major PSU manufacturers in the world.

It is nice to have, but not necessary. Well, at least I have a peaceful mind now. LOLL

 

[AntecRep]

Our European PSU's do not have a voltage switch.

AntecRep