Efficiency

Using the efficiency results from the previous page, we plotted a chart showing efficiency of the PF-850 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 PF-850 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.


The PSU doesn't register good efficiency with a 40W load since it fails to keep a reading of over 70%. Efficiency gets a nice boost with another 20W, but only on the last test does it manage to surpass the 80% efficiency mark. We would lie if we told you that we expected better results from an 850 W Bronze PSU.

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


Efficiency at 5VSB starts out pretty high, but drops off quickly. Our last test with a full load on this rail actually has efficiency drop below test #3. This is an indication that a 3 A load is near the limits of this rail.

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).


Kingwin rightly boasted that this PSU is compliant with the soon to come ErP Lot 6 2013 directive since phantom power is very low at 0.12 W. This means that you will save some money on your electricity bill over the long haul and that you, on top of that, won't waste energy, something that would, amongst other things, harm the environment.

Fan RPM, Delta Temperature and Output Noise

The cooling fan's speed (RPMs), along with the delta difference between input and output temperature, are illustrated in the following chart. The following results were obtained at 32°C - 35°C ambient.



The fan pushes a significant volume of air, and the Delta difference between input and output is, in conjunction with the energy dissipation of the PSU, pretty significant.

The following chart shows the cooling fan's speed (RPMs) and its output noise. We measure the fan's noise from a 1 meter distance. The background noise in our lab was close to 30 dBA during our testing.



As you can see, the fan is quite audible, even at its lowest speed. Apparently, this is not a suitable PSU for people with fine hearing.