Efficiency

Using the efficiency results from the previous page, we plotted a chart that shows the VSM750's efficiency at low loads and at loads equal to 20%-100% of the PSU's maximum-rated load.



The unit did pretty well with both low and normal loads, easily leveling with the Gold-certified competition. At low loads, it actually even beat a few high-end Platinum units.

Efficiency at Low Loads

In the next tests, we measured the VSM750's efficiency 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.


The VSM750 was very efficient at low loads, and its fan spun very slowly, which produced very little noise.

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 was efficient enough; however, we would like it to be a little stronger than the standard 2.5 A even mainstream PSUs can deliver on this rail nowadays.

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 on 5VSB).


Phantom power was low and in line with the ErP Lot 6 2013 directive.

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 37°C-46°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 20 dBA during testing, and the results were obtained with the PSU operating at 37°C-46°C ambient.



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



A quiet overall operation, and the fan spun slowly most of the time, producing very little noise. As we saw in our hot-box testing sessions, the fan's profile only ramps the fan up significantly above 40°C.