PE1950 - EnergySmart - any disadvantages?

John jses27 at gmail.com
Sun Oct 21 16:02:11 CDT 2007


On Sun, 2007-10-21 at 03:36 -0400, Kuba Ober wrote:
> On Tuesday 16 October 2007, michalwd1979 wrote:
> > Thanks for the info Faris.
> >  From my test it turns out that the efficiency of PSU is rather poor. 1 PSU
> > of dell2850 takes about 40-50W idle. In my configuration no loaded server
> > uses 180W (3 SCSI drives 2x 3GHz Xeon, 4G RAM). Fully loaded it needs
> > 240-250W. In fact I could save about 40W just by taking out one PSU. Some
> > other problem is cooling system.  6 high speed fans can take 70-80W alone
> > when running on full speed, much less when running on reduced speed. I am
> > using water cooling and only one PSU so I saved about 100W (0.4A).  Now we
> > are strongly thinking about making custom DC-DC PSU that will run directly
> > form 24V battery, thus we will not need UPS, that alone can take some power
> > just to covert energy 2 times. The problem is the connector to main board,
> > I need to get documentation somewhere.
The Main Board connector should be documented. Look for Dell specific
ATX style supplys with a +12v processor lead and should be a -3v PON
POFF switch lead. The rest can be figured out with a Voltage Meter +3,
-3, +5, -5, -12, +12. Maybe just might be on the outside of the power
supply, (connector pinout).
> 
> The power supply likely not only supplies the voltages, but also communicates 
> with the motherboard somehow (about temperatures at least).
> 
> You may try to look at the pins with an oscilloscope.
> 
> As for DC-DC converters, you may end up having to do custom PCB design and 
> whatnot: I presume that those supplies are pretty "stiff" on their 3.3V 
> outputs, and with the power they transfer you will have to know what you're 
> doing.
> 
> It's one thing to make a 1W DC-DC based on an application note. A PC supply 
> like you want to make will take at least a well equipped lab and someone with 
> some experience (or otherwise brilliant and really understanding physics). 
> You'd want it to be CE-compliant as far as emissions go, at least. Not a 
> small undertaking. As far as the server goes, with all the holes you've 
> punched through the case, it probably already is not in compliance for 
> emissions. Adding your own power supply will, at first try, likely drown out 
> most of the long, medium and shortwave radio in the neigboring apartments. 

Yea sure will, bring out the ferrite and torroids!! Also the capacitors.

> Not a nice thing to do. Power-efficient DC-DC converters run at lower 
> frequencies (say 50kHz) and they radiate like hell by default ;)

I smell a Ham Radio Operator?

> You may want to look into the power supply and find out whether it has a PFC 
> (power factor corrector). If it has, and it's a separate block, then the 
> DC-DC is designed to run off 300V and isn't that easy to interface to. If 
> there's no PFC, you will be able to power it with 100V DC going directly to 
> the far side of the rectifier -- those supplies take AC, rectify, and then do 
> DC-DC.
> 
> If there's a PFC, *and* you'd be brave, you can always rewind the primary on 
> the high-frequency transformer in the DC-DC converter with 1/3 of the turns 
> of a slightly thicker wire, so that the DC-DC would run on 100V DC instead of 
> 300V. A PFC is a step-up converter, and its output will be in 280-350V range, 
> depending on how it was designed. Getting rid of PFC and doing a DC supply 
> will save you 10-15% on efficiency (assuming your DC source is 100% 
> efficient). Measure it all first, of course.
> 
> You may just as well use a 9 x 12V batteries connected in series. They can be 
> on-line-charged using regular, line-frequency transformer-based power 
> supplies, as those will by default have a primary-to-secondary insulation 
> that can take a 100V offset. Not pretty, but simple, and way simpler than 
> making your own supply from scratch.
And by that means of using batteries, it will filter some of the RF
Hash. AC is Nothing but High Level RF.
> 
> By the way, the power supply should take ~120V DC without any modifications.  
> Oh, the joys of switching power supplies :)

I wonder if it is going to oscillate?

> 
> Cheers, Kuba
> 
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-- 
~/john

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