Randall R Schulz wrote:
On Saturday 09 February 2008 10:08, Philippe Landau wrote:
But many power supplies are only efficient when they don't operate close to full load. This seemed counterintuitive to me, so I decided to do a little looking around. According to the graph on page 14 of "Power Supplies: A Hidden Opportunity for Energy Savings" http://standby.lbl.gov/CEC_Workshop/Docs/Ecos_FinalReport.pdf this is not the case. It very much depends on the power supply in question. Today i would recommend buying one with over 80% efficiency. These often reach up to 85% efficiency, but only when they operate around 50% load: Power Supplies 101: A comprehensive guide Motherboards.org: http://www.motherboards.org/articles/guides/1487_7.html
The study you quote may be a bit outdated (2002) or be valid for cheap PSUs (Compaq). It is certainly good to check the characteristics of the PSU before you buy one: http://www.80plus.org/manu/psu/manu_psu.htm But as seen earlier in this thread, calculating the power consumption needs of the components used is not always easy. Kind regards Philippe --
Switching power-supplies have an efficiency peak when producing about 50% of their maximum rated output. However the curve on the low side of the efficiency peak is much steeper than that on the high side.
So my suspicion was mostly correct. A PSU that has more than twice the capacity that it will be called on to supply will waste significantly more power than one being used in the 50% to 100% range.
kind regards Philippe
Randall Schulz
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