Efficiency

Using the efficiency results from the previous page, we plotted a chart showing efficiency of the ST45SF-G 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 ST45SF-G 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 500W of capacity). This is important for settings where the PC is in idle mode with power saving turned on.


Efficiency is excellent at such low loads. The PSU manages to surpass 80% efficiency with only a 40 W load. That is amazing and fully matches this unit's target area since it will usually power a small system with low idle-power consumption. The fan is, unfortunately, already spinning at high RPM with such low loads, but we should note here that we conducted the above tests at 40°C ambient. Nevertheless, the ambient will easily reach 40 °C in a small chassis with strong components.

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: three at 100, 250, and 1000 mA, and one with the full load that the 5VSB rail can handle.


Efficiency at 5VSB starts really high, but paves off significantly. Nevertheless, we measured 78% efficiency during the third test and over 75% efficiency on the last test - not ground breaking, but definitely note-worthy since an SFX PSU achieved these scores.

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 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, as expected, low and passes the future ErP Lot 6 2013 requirements with flying colors.

Fan RPM & Delta Temperature

The following chart illustrates the cooling fan's speed (RPMs) and the delta difference between input and output temperature. The following results were obtained at 40°C - 45°C ambient.



The fan's speed can, at worst, exceed 3500 RPM, and the Delta difference between input and output at higher loads clearly shows that the fan does a good job of pushing the hot air out of the PSU's internals.