Efficiency

Using the efficiency results from the previous page, we plotted a chart that shows efficiency of the HG750 at low loads and at loads equal to 20% -100% of its maximum-rated load.



The HG750 proves to be very efficient at light loads; however, it falls short and behind most of the competition with normal loads. Although FSP used a unique design for the platform, it doesn't perform as expected since it fails to regulate its rails properly and isn't terribly efficient for a Gold-certified unit.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the HG750 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.

As has already been stated, the HG750 is efficient at light loads. The PSU also operated passively in these tests, while temperature inside the hotbox were between 36-38°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 is highly efficient because of the dedicated 5VSB board and its nice circuitry. We rarely see efficiency rise above 80% with Platinum and Titanium PSUs in these tests; however, the HG750 managed to rise to the occasion twice.

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).

As you can see, +12V's voltage was very high without a load on the rail. Please note that such a scenario is unrealistic since a real system always applies a load; however, this doesn't change the fact that we would like to see normal voltages at all times, and other PSUs do manage to keep their rails within the corresponding ATX specification in these no-load tests.

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 (RPM) and output noise follows. We measure the fan's noise from one 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 38°C-45°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.



Passive mode under normal temperatures doesn't last long, but the PSU isn't noisy with typical loads. However, noise-sensitive users should probably look for something else as the fan starts to make its presence felt at higher loads, becoming annoyingly loud at loads above 550 W.