Efficiency, Temperature And Noise
Efficiency
Our efficiency testing procedure is detailed here.
Using the results from the previous page, we plotted a chart showing the L9-CM-600W's efficiency at low loads, and loads from 10 to 110 percent of the PSU's maximum-rated capacity.
be quiet!'s latest lands right between the Gold and Bronze units on the average efficiency graph under normal loads, while it passes the Gold-rated Seasonic unit under light loads.
Efficiency At Low Loads
In the following tests, we measure the efficiency of be quiet!'s L9-CM-600W at loads significantly lower than 10 percent of its maximum capacity (the lowest load the 80 PLUS standard measures). The loads we dialed were 20, 40, 60 and 80W. This is important for representing when a PC is idle, with power-saving features turned on.
| Test # | 12V | 5V | 3.3V | 5VSB | DC/AC (Watts) | Efficiency | Fan Speed (RPM) | Fan Noise | PF/AC Volts |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 1.194A | 0.491A | 0.474A | 0.196A | 19.61 | 74.91% | 565 | 17.5 dB(A) | 0.764 |
| 12.200V | 5.016V | 3.365V | 5.037V | 26.18 | 115.1V | ||||
| 2 | 2.422A | 0.988A | 0.979A | 0.396A | 39.74 | 85.63% | 565 | 17.5 dB(A) | 0.786 |
| 12.184V | 5.012V | 3.361V | 5.030V | 46.41 | 115.1V | ||||
| 3 | 3.664A | 1.486A | 1.488A | 5.021A | 59.85 | 86.21% | 565 | 17.5 dB(A) | 0.967 |
| 12.119V | 5.028V | 3.356V | 5.021V | 69.42 | 115.1V | ||||
| 4 | 4.885A | 1.994A | 1.967A | 0.796A | 79.80 | 87.75% | 565 | 17.5 dB(A) | 0.972 |
| 12.120V | 5.020V | 3.352V | 5.013V | 90.94 | 115.0V |
Under light loads, efficiency is high overall, especially if we take into account that this is a Silver-rated unit. The fan is completely inaudible during these tests.
5VSB Efficiency
The ATX specification states that 5VSB standby supply efficiency should be as high as possible, recommending 50 percent or higher with 100mA of load, 60 percent or higher with 250mA of load and 70 percent or higher with 1A or more of load.
We take four measurements: one each at 100, 250 and 1000mA, and one with the full load the 5VSB rail can handle.
| Test # | 5VSB | DC/AC (Watts) | Efficiency | PF/AC Volts |
|---|---|---|---|---|
| 1 | 0.102A | 0.51 | 70.83% | 0.126 |
| 5.048V | 0.72 | 115.1V | ||
| 2 | 0.252A | 1.27 | 74.27% | 0.232 |
| 5.045V | 1.71 | 115.1V | ||
| 3 | 1.002A | 5.04 | 72.62% | 0.349 |
| 5.027V | 6.94 | 115.1V | ||
| 4 | 3.002A | 14.95 | 72.43% | 0.401 |
| 4.981V | 20.64 | 115.1V |
It's a shame that the 5VSB rail's efficiency is so low. Most likely the lack of a proper PWM controller is to blame.
Power Consumption In Idle And Standby
| Mode | 12V | 5V | 3.3V | 5VSB | Watts | PF/AC Volts |
|---|---|---|---|---|---|---|
| Idle | 12.173V | 5.045V | 3.367V | 5.054V | 6.06 | 0.402 |
| 115.1V | ||||||
| Standby | 0.10 | 0.018 | ||||
| 115.1V | ||||||
In the table above, you'll find the power consumption and voltage values of all rails (except -12V) when the PSU is idle (powered on, but without any load on its rails), and the power consumption when the PSU is in standby mode (without any load, at 5VSB).
Power consumption in standby is low, however this isn't enough to allow for high efficiency at 5VSB.
Fan RPM, Delta Temperature And Output Noise
Our mixed noise testing is described in detail here.
The first chart below illustrates the cooling fan's speed in RPM, and the delta between input and output temperature. The results were obtained at 34 °C (93.2 °F) to 47 °C (116.6 °F) ambient temperature.
The next chart shows the cooling fan's speed (again, in RPM) and output noise. We measured acoustics from one meter away, inside a small, custom-made anechoic chamber with internals completely covered in sound-proofing material (be quiet! Noise Absorber kit). Background noise inside the chamber was below 18 dB(A) during testing, and the results were obtained with the PSU operating at 36 °C (93.2 °F) to 45 °C (116.6 °F) ambient temperature.
The following graph illustrates the fan's output over the entire operating range of the PSU. The same conditions of the above graph apply to our measurements, though the ambient temperature was between at 28 °C (82.4 °F) to 30 °C (86 °F).
Up to around 450W, this PSU is almost inaudible. Under higher loads, you will be able to hear it if you're up close.
But my largest complaint would have to be voltage regulation (line regulation) under different load scenarios on page 6.
If only the PSU itself was outstanding as well:ouch:
For less than $10 more you can usually find excellent Seasonic and SuperFlower Leadex Gold units, which makes it really hard to say this PSU is anything more than "meh"
Not all group regulated designs are exactly the same way. We see in Seasonic's S12ii series a group regulated design that actually crossloads very well. This seems to be one of the worst on the ladder.
@Aris: Why is Inactive PWR_OK to DC_LOSS better at a higher value? Once the PWR_OK signal is dropped, wouldn't you want the unit to shut down as quickly as possible, not prolong it?
"The power-good signal lasts longer, so when it drops, the voltage level of the +12V rail is already below 11V."
When the pwr_ok to DC_loss is higher (*meaning that it has a positive , not negative value) that means that the motherboard will already have been shut-down. (*from what i've understand, at least)
Normally when AC is removed, the PWR_OK signal should be de-asserted at least 1ms before voltages go out of spec in order not to stress the VRMs of the mainboard and of other components (e.g. VGA, HDD, SSD, etc.).
The only way to address this issue is to have a circuit on the mainboard checking the input voltages and give the shut down order when these go out of spec. In other words to completely bypass the power_ok signal coming from the PSU. But this will cost money and after all a PSU oughts to follow ATX spec's guidelines.