Power Supply

[MD Willington]

Section 1.0 - Power supply selection.

Courtesy: AMD Builders Guide for Desktop/Tower Systems Article # 26003A — May 2002.

For reliable operation, the output of the power supply must be greater than the maximum total combined wattage usage for the system configuration.

In a standard single-user desktop/tower system, it should be apparent that the maximum wattage usage will be less than the combined total of all the components in the system.

The maximum wattage is less because it is almost impossible to concurrently use the maximum power of all the components. Therefore, a power usage factor should be used.

AMD suggests calculating the power supply minimum output capacity as the power required by the processor plus 80 percent of the total wattage for all the other components in a desktop/tower systems.

This 80 percent value is not a hard and fast value. The system builder's in-house testing may change the power-usage factor.

In addition to the overall wattage requirements, the builder must verify that the maximum voltage for the +5 V and +3.3 V power requirements for the system are less than the wattage limitation on the power supply for the +5 V and +3.3 V outputs.

What should be on your mind when making a Power supply purchase.

Whats the true capacity of your power supply? What I mean by that is not whats written on the side like "400W" I mean what are the amperage (A) specs for each voltage on the side of the power supply for:
3.3V = ?A
+5V =?A
+12V =?A
+5VSB =?A

Will I be able to use this in a future upgrade?

Is the Manufacturer known to be a quality power supplier manufacturer?

Is there enough capacity on the 12V line for now and for the future? The 12V line is now being used by even more power hungry devices, as opposed to the general myth that only 3.3V & 5.0V are all that matter.


Section 1.1 - UPS Selection.

Instead of writing a long winded article about this I have found some links for you to browse:

Courtesy: M+H Power Systems Pty. Ltd
http://www.mhpower.com.au/nikobe/html/sizingguide.html

Courtesy: UPSCI.com
http://www.upsci.com/UPS-selection.htm

Courtesy www.nooutage.com
http://www.nooutage.com/UPSGuide.htm

Again keep these questions in mind:

Will I be able to use this in a future upgrade?

Is the Manufacturer known to be a quality UPS manufacturer?

When in doubt look for reviews, google is your friend.

[arneson]

Re: Power Supply

May or may not be a good place for this but it's interesting,
http://www.smpstech.com/mtblog/elect...r_failure.html

[MD Willington]

Re: Power Supply

No problem, there are a lot more knowledgeable people out there...

MD

[yanz]

Re: Power Supply

May or may not be a good place for this but it's interesting,
http://www.smpstech.com/mtblog/elect...r_failure.html

"One of the most powerful methods for troubleshooting electronics is unplugging power."

http://www.smpstech.com/mtblog/

[yanz]

Re: Power Supply

about active pfc and why it's not about saving your electicity bill..

PF - http://www.pcper.com/article.php?aid...=expert&pid=11
PFC decoded - http://www.dansdata.com/gz028.htm
Work, Power & Apparent Power - http://www.pcguide.com/ref/power/ext/basics.htm
Testing Power Factor (PF) - http://www.systemcooling.com/tt_twv480-05.html
APFC Myth - http://www.silentpcreview.com/article28-page5.html

please, if someone here can explain it in his own understanding..

[davmax]

Re: Power Supply

I have read some of the links. The dansdata link is probably the simplest to understand and most accurate. One article has an error quoting passive PFC adds a capacitor. All PS have capacitor input and normally an inductor is used to add correction.

Active PFC usually comprises a pre convertor to over come the capacitor input effect and load changes. An example is covered in a TI abstract at: http://focus.ti.com/analog/docs/tech...ctName=slua369

Hope this helps.

[Galvanized]

Re: Power Supply

yanz, I found this PFC article better stated without being over technical, for me anyway.
http://www.rojakpot.com/showarticle....rtno=81&pgno=0
(look at Adrian's BIOS Guide)

Dan'sDATA states, that in this case efficiency takes a 10% hit but SPCR states a 3~5% loss. I prefer having APFC PSUs.

[gonzo0815]

Re: Power Supply

Well dealing now more and more with old and newer systems i `ve noticed that psu makers changed their produkt dramatikally.

In the beginning of the amd Athlon the important nummber of an PSu was the 3,3&5v combined power. This is still true for all systems which power the cpu and other stuff from the 5v and 3,3v rails, e.g mainboard lacking the 12v 4 pin conector ("p4" connector).
Famouse for beeing an current hungry beast are the k7s5a and simmilar desings and most asrock mainboards too (k7s8x**, only 2 phases and only 5v will need mutch power).There are board from all other vendors too.

Today most systems will power the cpu from the 12v line.
Now for an psu maker it is easy to increase the 12v power, due to the relative low amps which are needded. To save some bucks most new psu´s can only deliver a ver very small ammount of power on the 5&3,3v lines (e.g Amacrox , Fortron 150w combined power for an 500w psu or 130w combined power for a 350w psu).
It is clear, that any of that 500 or 600w rigs can`t stand an old soket A system, which don`t have an 4pin 12v connector.
And may be this is one of the reasons, why some DFI mainboards eat psu`s. They drain to mutch from the 3,3 and 5v and therefore kill the new psu`s.

At the moment i don´t know of any psu which can handle both, the high combined power and the high 12v power. probalby only the older higher wattage units can handle both, but they are rare to find.
May be, some ofnthe psu makers starts thinking and will make some decent units withoutn skimping something down.

[hkivan]

Re: Power Supply

At the moment i don´t know of any psu which can handle both, the high combined power and the high 12v power. probalby only the older higher wattage units can handle both, but they are rare to find.

These PSUs are capable.
http://www.2themax.com/power_mp_ep_x.html

They can supply 220w or more on 3.3v & 5v combined
while they also feature dual rail 12v.

[Galvanized]

Re: Power Supply

Another link reguarding Active PFC. Just happened on this one yesterday.

[yanz]

Re: Power Supply

yanz, I found this PFC article better stated without being over technical, for me anyway.
http://www.rojakpot.com/showarticle....rtno=81&pgno=0
(look at Adrian's BIOS Guide)

Dan'sDATA states, that in this case efficiency takes a 10% hit but SPCR states a 3~5% loss. I prefer having APFC PSUs.

that's a good link.

10%, i dont agree with that. in reality, it should be 5-10W (not in %). cmiiw.

[gonzo0815]

Re: Power Supply

It is absolutely not correckt to say that A-PFC PSu`s will be less efizient than others. In fact, all availible A-PFC PSU`S i`ve seen are in most cases far more eficient then those w/o.

It is clear, that the absolut best PSU without A-PFC will be more efficient compared with the absolut best of an A PFC unit. But those highly efficient P-PFC PSU are at the moment not availiable. Whereas many a-PFC units are availiable with efficiency numbers up to 85 % or even more.
So as long, as no non- or P-PFC psu will reach those numbers, this will be pure theoretical numbers.

[hkivan]

Re: Power Supply

Many people misunderstand about efficient & PFC.
Even some PSU reviews stated PFC lead to better efficient.
Those reviews just like a saleman fooling his customers.

In fact, most A-PFC PSUs are built with better components as compared with
their non/P-PFC counterparts. Better components sometimes lead to higher efficiency.
In this way, people will attribute higher efficiency to A-PFC.

[PeteS in CA]

Re: Power Supply

I think reviewers are just being imprecise. Whether active or passive PFC, compnents are added that dissipate power, so the efficiency of the P/S is reduced compared to non-PFC. However, due to the narrow conduction angle of non-PFC and the consequent potential for very high Neutral currents and IR drops in phase wires, PFC can improve efficiency in the power grid.

[starfury1]

Re: Power Supply

This post has slightly diverged I think off its original topic, anyway since its here

Think PeteS has more or less hit the nail on the head here as to why the big swing to pfc correction with SMPSU's

My understanding was the power companies had to worry about reactive/ apparent power losses.


How they do this I don't know but at some point I guess they have to correct or compensate for this, which probably costs $$$

Since new laws and specs have been brought in, I guess this is now being forced on to the MFR to produce more Grid friendly devices in respect to power factor correction.
(this may have been brought about by the power moguls putting pressure on the government...I don't know)

There is now a lot of garbage equipment that hangs off the mains system and switchers are just about everywhere these days, Even Wall warts are switchers so I suppose sooner or later MFR's were going to be forced to make better equipment

This I suppose has resulted in MFR's complying (cause they want to sell in these countries) but of course has added extra costs so their only way out is to use "Hype" to customers as to "why" they should buy their supplies over others...really half truths at best as far as the customer is concerned.

PeteS also raising an interesting point.(if not directly)

How much real power is expended to correct for reactive power losses ?.

Me, well at the end of the day if it results in an over all more efficient cleaner use of the grid which hopefully results in less fossil fuels being burn...then why not I don't mind paying a bit extra.

Don't know weather this would be the case but hope it would be

If I get a better designed, more efficient and better quality power supply because of it then all the better.

Just my thoughts on it

Didn't read it but looked interesting here

[gonzo0815]

Re: Power Supply

Well, the compensation issue is realy a $$ thing. In Germany any hughe profesionall elektricity consumer is urged to pay for it`s power factor, unless they compensate them by there own. This is a valid part in the contract. Thus any professionall equipment like elektronic fluorescent bulb balasts, motors etc. have A -Pfc or compensation caps for a long time here. And most companies invest in their own compnesation banks, if they have huge motors or other reactive devices. The other benefit is as mentioned before, the circuit brakers and the whol grid can be sized to the real values and the issues abouth strange potential differences betwen different facilities is reduced. Any way, the IT equipment was no the thing, people are aware of the problem. Thus it was largely ignored. From this point of view, i think it was a great idear from the EU, to make the compensation for devices abouth a significant power level mandatory. In the end it is a win for all stakeholders, environment, consumer and industry, if the cost for compensation are charged to the one who caused it.