Efficiency

Using the efficiency results from the previous page, we plotted a chart showing efficiency of the S12G-450 at low loads and at loads equal to 20% -110% of the PSU's maximum-rated load.



The S12G-450 performed very well with low loads and, again, resides right in the middle of the corresponding chart with normal loads.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the S12G-450 at loads much lower than 20% of its maximum-rated load (the lowest load the 80 Plus Standard measures). The loads we dialed were 40 W, 60 W, 80 W, and 100 W (for PSUs with over 500 W of capacity). This is important for settings where the PC is in idle mode with Power Saving turned on.

This PSU's low capacity gives it an advantage at low loads, and it did achieve high efficiency numbers in all of the above tests. The fan also spun at the same speed during all of our low-load tests; however, it is not dead silent as it produced close to 34 dBA, a mediocre reading in these tests even though the ambient temperature was 35°C.

5VSB Efficiency

The ATX specification states that 5VSB standby supply efficiency should be as high as possible and recommends 50% or higher efficiency with 100 mA of load, 60% or higher with 250 mA of load, and 70% or higher with 1 A or more of load.

We will take four measurements: one at 100, 250, and 1000 mA, each, and one with the full load the 5VSB rail can handle.

The 5VSB rail definitely isn't this unit's mainstay as its efficiency in the last two tests didn't even come close to 80%, which, admittedly, is a pretty high reading for the 5VSB rail.

Power Consumption in Idle & Standby

In the table below, you will find the power consumption and the voltage values of all rails (except -12V) when the PSU is in idle mode (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).

Phantom power is very low and easily meets the ErP Lot 6 2013 requirements.

Fan RPM, Delta Temperature & Output Noise

The cooling fan's speed (RPMs) and the delta difference between input and output temperature are illustrated in the following chart. The following results were obtained at 38°C-45°C ambient.



A chart that shows the cooling fan's speed (RPMs) and the output noise follows. We measure the fan's noise from 1 meter away, inside a small custom-made anechoic chamber whose internals are completely covered in specialized soundproofing material (Be Quiet! Noise Absorber Kit). Background noise inside the anechoic chamber was below 30 dBA during testing, and the results were obtained with the PSU operating at 38°C-45°C ambient.



The following graph illustrates the fan's output noise throughout the entire operating range of the PSU. The same conditions of the above graph apply to our measurements, but the ambient temperature was in-between 28°C and 30°C.



The PSU is quiet enough at up to 50% load and under normal conditions, although not dead silent. However, at higher loads, the fan also quickly increased its speed and output noise, which made it rather annoying with loads close to the unit's limit. A problem with designs where the mosfets and SBRs of the secondary side reside on the solder-side of the main PCB because the PSU requires adequate cooling to remove the heat, OEMs can't use a low RPM fan, which is why Seasonic abandoned this design element in their new KM3 platform their high-end units utilize.