Efficiency

Using the efficiency results from the previous page, we plotted a chart showing the efficiency of the X-750 at low loads and at loads equal to 20-110% of the PSU's maximum rated load.



For a discussion of these results, see the text at the end of the previous page.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the X-750 at loads much lower than 20% of its maximum rated load (the lowest load that the 80 Plus Standard measures). The loads that we dialed were 40, 60, 80, 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.


Efficiency at low loads is excellent, and the PSU operated, as you can see, in fanless mode during all of the above tests, although the ambient was between 35-40°C. This new KM3 platform is, compared to the KM2 platform, also notably more efficient at low loads.

5VSB Efficiency

The ATX spec states that the 5VSB standby supply's 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 mA, 250 mA, and 1000 mA each, and one with the full load that the 5VSB rail can handle.


Not only does the 5VSB rail offer tight voltage regulation for the standards of this rail, but it is also highly efficient and manages to surpass the 80% mark on the last two tests, which is not something we see often.

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).


Vampire power is much lower than the 0.5 W limit that the new ErP Lot 6 2013 directive requires, so Seasonic rightfully shows off the corresponding badge on the PSU's packaging.

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 40°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. The background noise in our lab was close to 30 dBA during testing.