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Old 08-17-2005, 09:51 AM   #1
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Default Power Supply Tutorial

There has been a new article posted.

Title: Power Supply Tutorial
URL: http://www.hardwaresecrets.com/article/181

Here's a snippet:
As an electrical device, the computer needs power in order for its components to operate properly. The device responsible for supplying power to the computer is the power supply. In a short way, we co...

Comments on this article are welcome.
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Old 11-15-2005, 02:21 PM   #2
bhesterman
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Default Power factor correction DOES benefit end users

Power supplies with power factor correction have two main benefits for end users:

1. Harmonic currents are greatly reduced. This makes electrical facility design much easier, and reduces the cost of the electrical system.

2. Harmonic currents cause significant losses in the power system. Using power factor corrected supplies can provide energy savings of around 5%.

Reference:

Costs and benefits of harmonic current reduction for switch-mode power supplies in a commercial office building
Key, T.S.; Jih-Sheng Lai;
IEEE Transactions on Industry Applications,
Volume 32, Issue 5, Sept.-Oct. 1996 Page(s):1017 - 1025
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Old 04-07-2006, 03:02 PM   #3
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Default Errors

There are a number of technical errors in this article.

1. There is no such thing as a "BTX" power supply. 24-pin main power + 4-pin P4 = ATX12V (v2.0) OR 24-pin main power + 8-pin P4 = EPS12V. Many recent power supplies meet both specs with convertible 20/24-pin and 4/8-pin connectors.

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Old 04-11-2006, 09:26 AM   #4
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Hi,

You are 100% right. Thanks to your tip I updated this tutorial correcting these errors and also adding info about new small form factors. Enjoy!

Once again, thank you very much for pointing out the errors.

Cheers,
Gabriel.
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Old 04-17-2006, 08:37 AM   #5
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Pretty good article. Much better than most PSU reviews out there which just say "Ooo, it's pretty" and "voltage is within tolerance" and "look at how many watts it has". I was glad to see the mention of effeciency. That's one of the more important factors to me for a PSU.

As for PFC, this is also important if you have a UPS. Say you have a PSU without PFC and are drawing 100 watts of DC power. If you have a decent PSU, you might have 75% efficiency. That means 133 wattts of AC power. If you have Active PFC, your VA rating will also be 133. If you have passive PFC, you're looking at 190VA. No PFC, you're talking 266VA. That can make a big difference in how big of a UPS you need, especially if you plan on running a couple of PCs on the same UPS.
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Old 05-30-2008, 12:05 AM   #6
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Default Well I guess...

... that answers the question I emailed to you a couple of days back about your recommended loading

40-60%.

I'm a bit of a cheapskate so I think I'll continue keeping it tight at 50-60% :P

Although I have to say I find those calculators like the Outervision one misleading because they don't make it clear that the figure it comes out with is the recommended rating of a good quality PSU, not the actual power the components would draw. It's a relatively minor beef but on every forum I've seen people use those figures then double them and start suggesting things like the Corsair VX550W for an E8400 & 9600GT setup that'd barely manage to draw 100W DC. So I think they should make it clearer.

I don't have the pro version so maybe the amperage values they give for the +12V rail(s) are accurate and not exaggerated values.

But yeah, with all these high powered PSUs being reviewed people tend to forget that the vast majority of single socket CPU & single slot graphics systems can be comfortably powered by the Zalman 360W or Antec EarthWatts 380W, the rare exceptions usually being systems with single slot graphic solutions that contain more than one GPU.

I found the use of "alternating voltage" on the first page to be slightly off putting. I know what you mean but I don't think it's technically correct. Not an electrician or electrical engineer though, so maybe it is technically correct.

Great overview of PSUs and I'll certainly be directing anyone who's curious to this. Thanks for the good work, once again.
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Old 05-30-2008, 11:58 AM   #7
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Hello,

Thanks for the compliments.

Yes, I totally agree. Lots of users are buying high-wattage PSUs without needing them.

As for alternating voltage, this expression is absolutely correct. You said yourself: you are not an engineer...

Electricity starts with current (I), voltage (V) and resistance (R). Current and voltage are two completely different things. Most people refer to the wall socket as "alternating current" while the correct term would be "alternating voltage". The voltage present on the power grid alternates in a sine waveform at 60 Hz. For example, on a 115 V network the voltage starts at 0 V, grows up to 161 V, then goes down to 0 V and then starts to go down up to 161 V, then goes back to 0 V. This cycle repeats itself 60 times per second. As you can see, the voltage alternates, thus the name alternating voltage.

More here: http://en.wikipedia.org/wiki/Alternating_current

By the way 115 V is the RMS voltage. The peak voltage would be 161 V (115 V * SQR(2)). More here: http://ourworld.compuserve.com/homep...tt/elect39.htm

Cheers,
Gabriel.
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Old 05-30-2008, 05:16 PM   #8
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I understand how AC power works I'd just don't really recall seeing it referred to as alternating voltage before, which is why I had "technically" in front of the word correct. I suppose I probably should have used "colloquially" or "commonly" instead of "technically" since as you point out it is indeed a more technical description than alternating current is.

I appreciate you clearing it up for me.

It's funny reading through those links how much the year of studying E&EE comes back to me.
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Old 09-20-2008, 05:01 AM   #9
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Apologies in advance for resurrecting a dead thread; however as it does seem to be the most appropriate place to ask my question:

Quote:
Originally Posted by tantryl View Post

Although I have to say I find those calculators like the Outervision one misleading because they don't make it clear that the figure it comes out with is the recommended rating of a good quality PSU, not the actual power the components would draw. It's a relatively minor beef but on every forum I've seen people use those figures then double them and start suggesting things like the Corsair VX550W for an E8400 & 9600GT setup that'd barely manage to draw 100W DC. So I think they should make it clearer.
I've been trying to diagnose some hardware problems, and the Outervision calculator gave me a figure of 275W - though as most of the fans on the motherboard were smaller than the options they gave, this is probably an underestimate.

If I take the advice in the article, I should be looking for a PSU rated approxmately double that figure, i.e. 550W, and the 300W supply put there by the OEM is probably inadequate. However, the forum comment quoted above seems to contradict this. Should I indeed be looking for a 550W PSU?

Thanks for any help!
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Old 09-22-2008, 07:58 AM   #10
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Hello,

My recommendation on the tutorial is for "the best scenario". Meaning, if you really is a user concerned with efficiency, you should get a PSU that is twice what you PC needs so you can enjoy the highest efficiency your PSU can give.

However if you calculated that your PC pulls 275 W and you have in fact a 300 W PSU it is definetely time to upgrade your PSU. Especially because probably you have a "generic" unit that won't be able to deliver its labeled power continously.

A good power supply between 450 W and 600 W is the recommended to a mainstream user. Go to our review section and you will find several models we recommend on this range like Zalman, OCZ, Corsair, etc.

I hope I have clarified.

Cheers,
Gabriel.
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