I just purchase a Silverstone Power Supply Unit (PSU) for my PC.
I am amaze with the PFC (Power Factor Correction) rating of over 0.96, which, according to some indicators, means it's 96% efficient. (4% wastage as heat).
Since it's a new unit I dare not to open up the PSU to see what type of electronics they are using.
So I post the question here ----
Can anyone tell me what type of Power Conversion Electronic Devices they use in those high PFC rating PSU?
Thank you all !!!
Please do not confuse Power Factor Correction (PFC) with power supply efficiency. They are two separate items. PFC can be either active or passive, but usually alters the highly capacitive input of SMPSs.
Google "PFC".
"UCLAN"
** OK so far.** Hmmmm...
** TOTAL BOLLOCKS !!!
They are not capacitive, there is no phase angle.
Active PFCs correct WAVEFORM distortion.
...... Phil
Gee, thanks. [Red flag warning!!!]
Careful, a hint of ignorance is showing.
And it's finally out. He's a total loon.
There is a big 400vdc capacitor (or two 200vdc caps in series) just after input rectifiers on the AC input. Note C5 and C6 on:
They charge to the peak value of the input AC voltage, or 1.414 times the RMS value. Since the cap(s) draw their maximum current when at lowest charge (zero cross-over point), and draw their least amount of current when charged to their highest point, the current waveform
*leads* the voltage waveform by 90 degrees. [Maximum current is at the same time as minimum voltage; minimum current is at the same time as maximum voltage.]On Sun, 26 Apr 2009 22:48:56 -0700, UCLAN put finger to keyboard and composed:
As much as I dislike the man, he's right.
Look at Fig 6 on page 2 of the application note you linked to elsewhere in this thread.
PA could easily put at end to this argument by enlightening everyone with his own example ...
... but instead he chooses to elevate himself by demeaning others.
- Franc Zabkar
-- Please remove one 'i' from my address when replying by email.
voltage.]
He is. Actually, from modelling, I've found a big hulky inductor between the rectifier and storage caps is pretty good at correcting harmonics. Trouble is, they're big, heavy and expensive.
Sadly active PFC produces even more RF 'hash' that needs to be dealt with.
Sadly so.
Graham
voltage.]
It does show that the current leads - look at how it's not positioned symmetrically about the 90 degree point, for example. It's not a 90 degree lead, of course, but it's still a lead.
Mind you, I think the graph is wrong. When it's flowing, the current into a capactor should be proportional to the rate of change of voltage. So you should see a rapid rise once the input voltage goes above that already on the capacitor, followed by a progressive reduction towards zero (plus the load current) at the voltage peak. I suppose you'd get something closer to what's shown if there were an inductor in series with the supply.
Sylvia.
On Wed, 29 Apr 2009 12:28:36 +1000, Sylvia Else put finger to keyboard and composed:
voltage.]
A bigger capacitor would result in less ripple, which means less lead. If you were relying on intuition alone, you would expect that the PF would move closer to unity. In fact the PF actually becomes worse.
See the calculations in Phil's example.
- Franc Zabkar
-- Please remove one \'i\' from my address when replying by email.
maximum
voltage.]
With a larger capacitor, you get less lead, but higher instantaneous currents. My intuition would be that the net result is far from obvious.
However, the higher current for shorter periods means higher harmonic currents, which don't contribute to the power, so it wouldn't surprise me that the PF would go down.
Sylvia.
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