be quiet! Straight Power 11 550W Platinum Power Supply Review

how can it be both;

+ FORCompatible with the alternative sleep mode

&

- AGAINSTNot compatible with the alternative sleep mode

??

Great write up, Aris.

I was not aware that the Intel PSU specs were coming out this summer (July 2020), which is great. BTW, take a look at the ripple graph on page 3. I think the Y axis is labelled wrong. Also, why no data on the 115VAC holdup? That is critical for people using this PSU with a standard UPS. Most of desktop UPS systems (think: inexpensive) are standby / line interactive and have a change over relay with transfer times in the 4-20mSec time range. Any PSU that is lower than that will have problems keeping the CPU alive during an outage. Too bad there is not a signal from the PSU to the CPU to power back. That signal could be used everywhere to cause SSDs and RAID arrays to go into save mode, and other subsystems to power down (Ethernet, USB, audio, etc.).

The Cybernetics Labs testing methods are spot on for the "how and why". There are minor tweaks that I would make, but overall, excellent testing methodology. The UPS market has cheated on efficiency for decades by testing a cold UPS for the product documentation. Everything should be at thermal steady state for true efficiency numbers, and at realistic operating conditions. The only parts that benefit from being warm are the electrolytic caps, except for their lifetime. I believe it is still true that all electrolytic caps have a decrease in ESR as they get warmer, up to a point depending on the electrolyte used. Everything else gets worse efficiency with heat: MOSFETS, XFMR, filter inductors, etc.

It is good to see better efficiency numbers in lower power PSUs. I searched for along time on my NAS build for at least a 80+ gold rated 200-250W PSU. I finally found an FSP 250W unit that was in an SFX package. A great article would be one who has the better/best low power PSUs especially in the area of efficiency.

Several points that I believe get overlooked in thinking about efficiency:

How much energy are you going to use to cool the building that the PSU is in? Usually around 50% of the total PSU power used for the months that HVAC is being used. This also gets overlooked with cost comparisons for LED bulbs versus incandescent bulbs. The HVAC savings is enormous.
The concept that the payback period for a higher cost efficient PSU does not give good ROI. I reuse most of my PSUs unless the caps look poor or I have had it being used at over 50-60% rated power for much of its life. With PSU getting warranties of 5years+, the added cost should be amortized over a longer period. Maybe over two chassis builds?
Thanks for the great article.

BR,
Charles

JohnBonhamsGhost said:

how can it be both;

+ FORCompatible with the alternative sleep mode

&

- AGAINSTNot compatible with the alternative sleep mode

??

this is an obvious error. It IS compatible with the alternative sleep mode. Already asked to fix this.

chaz_music said:

Great write up, Aris.

I was not aware that the Intel PSU specs were coming out this summer (July 2020), which is great. BTW, take a look at the ripple graph on page 3. I think the Y axis is labelled wrong. Also, why no data on the 115VAC holdup? That is critical for people using this PSU with a standard UPS. Most of desktop UPS systems (think: inexpensive) are standby / line interactive and have a change over relay with transfer times in the 4-20mSec time range. Any PSU that is lower than that will have problems keeping the CPU alive during an outage. Too bad there is not a signal from the PSU to the CPU to power back. That signal could be used everywhere to cause SSDs and RAID arrays to go into save mode, and other subsystems to power down (Ethernet, USB, audio, etc.).

The Cybernetics Labs testing methods are spot on for the "how and why". There are minor tweaks that I would make, but overall, excellent testing methodology. The UPS market has cheated on efficiency for decades by testing a cold UPS for the product documentation. Everything should be at thermal steady state for true efficiency numbers, and at realistic operating conditions. The only parts that benefit from being warm are the electrolytic caps, except for their lifetime. I believe it is still true that all electrolytic caps have a decrease in ESR as they get warmer, up to a point depending on the electrolyte used. Everything else gets worse efficiency with heat: MOSFETS, XFMR, filter inductors, etc.

It is good to see better efficiency numbers in lower power PSUs. I searched for along time on my NAS build for at least a 80+ gold rated 200-250W PSU. I finally found an FSP 250W unit that was in an SFX package. A great article would be one who has the better/best low power PSUs especially in the area of efficiency.

Several points that I believe get overlooked in thinking about efficiency:

How much energy are you going to use to cool the building that the PSU is in? Usually around 50% of the total PSU power used for the months that HVAC is being used. This also gets overlooked with cost comparisons for LED bulbs versus incandescent bulbs. The HVAC savings is enormous.
The concept that the payback period for a higher cost efficient PSU does not give good ROI. I reuse most of my PSUs unless the caps look poor or I have had it being used at over 50-60% rated power for much of its life. With PSU getting warranties of 5years+, the added cost should be amortized over a longer period. Maybe over two chassis builds?Thanks for the great article.

BR,
Charles

Hi Charles, and thank you for your comments.

The hold-up time is almost identical between 115V and 230V. The change is in the inrush current. I agree with you, the hold-up time is of immense importance.

CL ripple graph in page 3, I cannot find anything out of order.

If you have any suggestions on how to improve the Cybenetics methodology, they always hear opinions and are ready to make changes, if those are for the best.

About efficiency, diodes have lower voltage drops at increased temperatures as well, and this plays a major role especially in bridge rectifiers.

Thank you for the other two points you mention. Indeed the cost of dealing with the added thermal load of lower efficiency PSUs is significant.