Efficiency

Using the efficiency results from the previous page, we plotted a chart showing the efficiency of the GX-F750 at low loads and loads equal to 20%–100% of the PSU's maximum-rated load.



Under light loads, the GX-F750 doesn't perform all that well compared to offering with similar specifications. With normal loads, it does better, which nets it a higher spot in that chart.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the GX-F750 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.


Based on our past experiences with this platform—this is the third sample with the platform we are testing—we expected higher efficiency at light loads.

5VSB Efficiency

The ATX specification, along with CEC, ErP Lot 3 2014, and ErP Lot 6 2010/2013, states that 5VSB standby supply efficiency should be as high as possible, recommending, among others, 75% or higher efficiency with 550mA, 1A, and 1.5A of load. The PSU should also achieve more than 75% efficiency at 5VSB with its full load, or 3A if its maximum current output on this rail is higher than 3A.

We will take six measurements: one at 100, 250, 550, 1000, and 1500mA, each, and one with the full load the 5VSB rail can handle.


The 5VSB rail is not that efficient. We would like to at least see a reading above (or even close to) 80%.

Power Consumption in Idle and Standby

In the table below, you will find the power consumption and 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 a load at 5VSB).


Vampire power is quite low.

Fan RPM, Delta Temperature and 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 38–47 °C ambient.



A chart that shows the cooling fan's speed (RPMs) and output noise follows. We measure the fan's noise from a meter away, inside a hemi-anechoic chamber. Background noise inside this hemi-anechoic chamber was below 6.0 dBA during testing, and the results were obtained with the PSU operating at 38–47 °C ambient.



The following graph illustrates the fan's output noise throughout the entire operating range of the PSU. The same conditions as for the above graph apply to our measurements, but the ambient temperature was between 30 °C and 32 °C.



The fan profile should not be as aggressive since the PSU's efficiency reduces the thermal loads the fan has to deal with by a lot. This is not a noisy PSU, but it could be considerably quieter with an appropriate fan profile. Things would fare even better with a semi-passive mode.