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Author Topic: Computer power supply Active PFC (power factor correction) THE TRUTH  (Read 3027 times)

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Offline Kiriakos GR

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Since the year 2007 and later my preference of watt power for my computer about power supply of choice, this was in the range of 700 ~ 850 Watt.

Every time which I had to connect my PSU to Mains (220V), at first connection there was always a huge instant spike of current.
My APC 1000XL UPS this was able to sense it, and over-current alarm beep sound was triggered.

Since 2007 and up to date, I did come across of PSU product reviews delivered due computer enthusiast reviewers.
Unfortunately for them, and for us, they lucking electronics training, and neither have a clue of how many handbooks you have to read in order to understand pulsing power supply basics and design.

The long story in sort, when a PSU this includes Active Power Factor Correction circuit, it is expected this to activated at first few ms of time after power connection.

ON-SEMI brand and developer of active PFC IC’s, it does clearly mention, that this is unavoidable phenomenon, for any PSU this including or using Active PFC electronics circuit.
It is in the nature of switching power supply, to create current spikes.
PFC this has exclusively to do with AC current waveform adjustment and control.

Below are two diagrams, first one this demonstrate before and after current curve and of how Active PFC this corrects the current waveform.

The second diagram it’s a sample of current waveform without any PFC correction.
In this one you can see with your own eyes, peak values of AC current.
 
An electrician at the application of electric motors, he has to take in to the calculation the inrush current, as the motor will require a much higher current for a few seconds of time until motor rotation speed this becomes optimal.

Switch mode power supply these has a much faster start-up time, and because of that any start-up current spikes they can be measured with different tools than the ones measuring motors inrush current.

The conclusion, SMPS current spikes prior PFC gets in control, they are unavoidable.
PSU product reviews them trying to compare current spikes caused within few ms of time as indication of PSU build quality, they are trash.

It would be more of value
if PSU product reviewers were focus to demonstrate oscilloscope screen (screen shots) as the 80PLUS program does, which these demonstrate of how well and in phase are both voltage and current waveforms, as soon the PSU this is fully active.     

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Offline Andrew-88

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Re: Computer power supply Active PFC (power factor correction) THE TRUTH
« Reply #1 on: November 04, 2022, 10:37:19 AM »
Second screenshot and explanation, this is most powerful visual example even for the eyes of people without in-depth electrical training!  :)

At computer products reviews, 98%of reviewers they are anonymous trespasser.
Taking advantage of other people ignorance this is all that they are capable to deliver as content.

You should be thankful to Seasonic, their move about to deliver product samples in your hands, this become your motivate for you to dig further and explore such PSU technologies, and even find and study such handbooks.  8)



Offline Kiriakos GR

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Re: Computer power supply Active PFC (power factor correction) THE TRUTH
« Reply #2 on: November 04, 2022, 04:50:13 PM »
Second screenshot and explanation, this is most powerful visual example even for the eyes of people without in-depth electrical training!  :)

At computer products reviews, 98%of reviewers they are anonymous trespasser.
Taking advantage of other people ignorance this is all that they are capable to deliver as content.

You should be thankful to Seasonic, their move about to deliver product samples in your hands, this become your motivate for you to dig further and explore such PSU technologies, and even find and study such handbooks.  8)

I am thankful to Seasonic, but my nerves they are now look as guitar strings.
Other people PSU product reviews these do not qualify as facts.

I am now rediscover the functions and capabilities of my Oscilloscope along differential voltage probe and current probe.
Its of importance to setup oscilloscope and probes, so all incoming waveforms to be in phase.
With current probe there is an arrow at the jaws, you cannot go wrong with that.
But with voltage wires, its your responsibility to connect active phase and neutral cables correctly, or else you will see everything with a not easy to explain phase error ;D.
Now I did solve this problem too, by the help of my resistive load (expected waveform shape), along using my brain cells by reviving memories of school training.

Load testing its about using specific tools and skills, if you do not have both? (by paying the heavy price) then your story its similar to fairy tail. 
 
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