Test Setup

All measurements were performed using ten electronic loads (seven Array 3711A [300 W each] and three Array 3710A [150 W each]), which are able to deliver over 2500 W of load and are controlled by a custom-made software. We also used a Picoscope 3424 oscilloscope, a CHY 502 thermometer, a Fluke 175 multimeter, and an Instek GPM-8212 power meter. Furthermore, in our setup, we included a wooden box, which, along with a heating element, was used as a hot box. Finally, we had at our disposal four more oscilloscopes (Rigol 1052E and VS5042, Stingray DS1M12, and a second Picoscope 3424) and a CEM DT-8852 sound level meter. In this article, you will find more details about our equipment and the review methodology we follow. Finally, if the manufacturer states that the maximum operating temperature of the test unit is only 40°C, then we try to stay near this temperature; otherwise, we crank up the heat inside the hotbox up to 45-50°C.

Voltage Regulation Charts

The following charts show the voltage values of the main rails, recorded over a range from 60 W to the maximum specified load, and the deviation (in percent) for the same load range.

5 VSB Regulation Chart

The following chart shows how the 5 VSB rail deals with the load we throw at it.

Efficiency Chart

In this chart, you will find the efficiency of the HX850 at low loads and at loads equal to 20-100% of the PSU’s maximum rated load.

Voltage Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the efficiency of the HX850. The applied load was equal to (approximately) 20%, 40%, 50%, 60%, 80%, and 100% of the maximum load that the PSU can handle. In addition, we conducted two more tests. In the first test, we stressed the two minor rails (5 V and 3.3 V) with a high load, while the load at +12 V was only 2 A, and, in the second test, we dialed the maximum load that the +12 V rail could handle, while the load on the minor rails was minimal.

The PSU clearly proved that it can deliver its full power continuously even at above 50°C ambient temperature. Also, its efficiency is quite high and we are pretty sure that it easily surpasses the 80 PLUS Gold levels. As you can see, it peaks with 50% load at 91.29%, a pretty high reading for a Gold-certified unit. Regarding voltage regulation, in general, it is tight enough (for our standards) and above average of the PSU's category.
Although the unit goes fanless at low ambient temperature, we didn't give it the chance to do so since from the start we cranked up the heat inside the hot box. Now, for the 'up to 50% load test', the fan was quiet enough, but, afterwards, it increased its speed and noise output, not to an annoying degree though. Even at full load with over 50°C ambient the fan could not be characterized as noisy, at least in my opinion.

Efficiency at Low Loads

In the next tests, we measured the efficiency of the HX850 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.

At low loads, the unit registered decent, to say the least, efficiency since our monitoring software didn't measure below 70% efficiency readings, even with 40 W of load. As you can see from 40 W to 60 W, load efficiency rose to 77% and with 80 W of load and more, it easily passed the 80% mark.

5 VSB Efficiency

The ATX specification states that the 5 VSB 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 5 VSB rail can handle.

At 5 VSB, efficiency is pretty high even at test #1. In the last two tests, it may not pass 80% but still 77-78% efficiency at this rail is something that shouldn't be taken lightly.

Power Consumption in Idle & Standby

In the table below, you will find the power consumption and the voltage values of all rails (except -12 V) 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 5 VSB).

Phantom power is very low at this unit and barely exceeds 0.1 W, so the requirements of ErP Lot 6 2010 and 2013 directives are easily met.