be quiet! 350w SFX Power PSU

Simulated Load Testing

Simulated Load Testing
To provide accurate and consistent results in all of our PSU testing, Overclock3D uses professional grade DC electronic load equipment capable of placing a sustained load of 3690w across a total of six rails (including +5vsb and -12v) on the PSU! This is achieved by using a combination of SunMoon and Analogic electronic load equipment which allow us to adjust amperage loads in increments as small as 0.01A while also measuring voltage and wattage readings on-screen.
During today's tests, we will be placing the be quiet 350w SFX PSU under 25%, 50%, 75% and 100% load levels at room temperature. Unfortunately, due to the size of the PSU on test today no 50°C 'hot-box' testing could be performed.
be quiet! 350w SFX Results @ Room Temperature
   +3.3v  +5.0v  +12v  +5vSB  -12v  AC Watts /
 DC Watts
 Efficiency  Intake /
Δ Temp
3.75A 4.00A 4.25A  0.62A  0.12A 105w /
 83.80% 27.2°C /
3.37v 5.09v 11.92v 5.14v  -11.90v
7.50A 8.00A 8.50A 1.25A  0.25A  205w /
 85.85%  27.0°C /
11.94v 5.05v  -11.93v
11.25A 12.00A 12.75A  1.87A  0.37A  309w /
 85.11%  26.5C /
3.33v 4.98v 11.94v 4.96v -11.98v
15.00A 16.00A 17.00A 2.50A  0.50A 419w /
83.53%  25.6°C /
3.31v 4.92v 11.96v 4.88v -12.01v
15.00A 16.00A 1.00A 0.00A 0.00A 175w /
78.85% 27.2°C /
3.34v 4.75v 12.45v 5.16v -12.50v
 1.00A  1.00A  29.50A  0.00A  0.00A 0w /
00.00%  00.0°C /
0.00v 0.00v 0.00v 0.00v -0.00v
 15.00A  16.00A 23.00A  2.50A  0.50A  507w /
82.84%  27.3°C /
3.31v 4.93v 11.88v 4.86v -12.06v
Starting with the results from Test 1-4 which best represent the PSU under normal usage, we can see that the +3.3v and +5v rails on the unit are reasonably stable with a drop of 0.06v and 0.17v respectively. The real shock however comes when we take a look at the results from the +12v rail which actually INCREASED by 0.04v from idle to full load. This normally occurs when the voltage regulation on the PSU overcompensates for the load and can actually end up reducing the total power output as a result. Efficiency, on the other hand is very good for such a small unit with 85% being achieved at a load of 180 - 260w.
Although it is quite unlike me to comment on the noise of a PSU given how loud the load testing equipment is, this is undoubtedly going to be an important factor in the decision of anyone purchasing a SFX PSU. Therefore, using my ear alone as the only measuring device, I can tell you that up to 200w load the SFX Power is very quiet. However as the load increases to 260w the 80mm fan speed increases significantly to the point where I imagine you'd easily be able to hear it across the room. At 350w I could actually hear the PSU above the load testing equipment, which is never a good sign! 
T5 moves into the cross-load teritory and here we can see that the be quiet isn't so happy with a heavy load on the +3.3v and +5v rails and only a small load on the +12v rail. Voltages for the +5v rail hit a rather poor 4.75v and the +12v rail shoots up to 12.45v. Additionally efficiency during this test drops to around 78%. In T6 the cross-load is reversed with a minimal load being placed on the +3.3v and +5v rails and the rest on the +12v rail.  Unfortunately during this test the be quiet unit refused to power on with anything above 25A on the +12v rail and therefore failed the test. What we do need to remember at this point though is that these cross-load results are highly unlikely to be reproduced by any PC system (especially a HTPC/SFF PC) in the real world. Only if you was intending to use the unit purely to power 12v devices and nothing else would this become an issue.
T7 sees the SFX Power hit a maximum output of 420w - 70w higher than that if its rated output. Given the size of the unit this is actually pretty respectable and shows that the unit has a little extra power to give should the need arise. At this load the voltages are still very respectable and efficiency is just shy of 83%.
be quiet! 350w SFX Scope Results @ Room Temperature 
   +3.3v  +5.0v  +12v
T1_3.3V T1_5V T1_12V
t2_3.3v t2_5v t2_12v
t3_3.3v t3_5v t3_12v
t4_3v t4_5v t4_12v
t5_3.3v t5_5v t5_12v
T7_3.3 T7_5 T7_12
For those of you not familiar with the term 'ripple', this refers to the small fluctuations in voltage that occur in all PSU's on a milisecond scale. Large quantities of 'ripple' on a PSU can damage or kill components in your PC over time and therefore testing a PSU's performance in this area is just as important as any other part. Unfortunately ripple cannot be measured using a standard multimeter and requires a specialist device called an oscillioscope. The results you see above are taken from our Rigol 25Mhz 400MSa/s scope that can save 'screenshots' of its data to a USB memory stick.
A quick glance at the graphs above shows the most unruly rail to be the +3.3v one. However, even here the SFX Power manages to keep the ripple at just over 40mVpp in Test 4 and just under 40mVpp in Test 7. The +5v and +12v rails perform even better in comparison topping out at 21.6mVpp and 25.6mVpp respectively during Test 4. Only during the cross-load testing in T5 does the +5v rail break 50mVpp showing that the SFX Power isn't too keen on cross-load situations.
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Most Recent Comments

22-09-2009, 17:22:50

Very nice unit that, the size of it is great, whilst performance is sitll good. Looks nice as usual too!

Shame it's noisy at full load, but for the applications it's aimed at, will it ever reach full load?Quote

22-09-2009, 17:43:55

My initial thoughts were that they've done really well to get it so small, but it's a shame about the noise. Then exactly like Peter I wondered how likely it is for a HTPC system to hit full load.

Depends on if you use it for Bluray playback (thus a beefy CPU) or not I guess.Quote

22-09-2009, 18:37:59

Perfect timing.

Need a HTPC PSU as my relative's HTPC PSU just busted!

Gotta love OC3D.Quote

22-09-2009, 19:14:49

Originally Posted by name='zak4994'
Perfect timing.

Need a HTPC PSU as my relative's HTPC PSU just busted!

Gotta love OC3D.
Glad to be of service

@Peter/VB, yeah I doubt in most systems it will come close to 350w so the high load noise won't really be too much of an issue. But on the other hand I do have a Q6600 HTPC with a HD4850 and 3x1TB HDD's, so I might give it a slightly hard time Quote

22-09-2009, 19:15:40

Just wanna make sure before I order, will this fit in an HP Slimline PC?

Don't wanna thread hijack. lolQuote

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