Test Setup

All measurements are performed utilizing nine electronic loads (six Array 3711A, 300W each, and three Array 3710A, 150W each), which are able to deliver over 2000W of load and are controlled by a custom made software. We also use a DS1M12 (Stingray) oscilloscope, a CHY 502 thermometer, a Fluke 175 multimeter and an Instek GPM-8212 power meter. Furthermore, in our setup we have included a wooden box, which along with a heating element is used as a Hot Box. Finally, we have at our disposal two more oscilloscopes (Rigol 1052E and VS5042) 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.

Voltage Regulation Charts

The following charts show the voltage values of the main rails, recorded over a range from 70W to the maximum specified load, and the deviation (in percent) for the same load range.

Efficiency Chart

In this chart you will find the efficiency of HM-650 at low loads and at loads equal to 20-100% of PSU’s maximum rated load.

Voltage Regulation and Efficiency Measurements

The first set of tests reveals the stability of voltage rails and the efficiency of HM-650. The applied load equals to (approximately) 20%, 40%, 50%, 60%, 80% and 100%, of the maximum load that the PSU can handle. In addition, we conduct two more tests. In the first we stress the two minor rails (5V & 3.3V) with a high load, while the load at +12V is only 2A and in the second test we dial the maximum load that +12V can handle while load at minor rails is minimum.


Efficiency is at the regular levels for an 80 PLUS Bronze PSU (don't forget we test with 230V so efficiency is 1-2% higher than 115V input). Voltage regulation at +12V is under 2%, so tight enough, at 5V is 3.5% and at 3.3V is over 4%. We would like to see tighter voltage regulation on the minor rails but we should note that the most important rail of all is +12V and on top of that almost no contemporary system will draw so many Amps from the minor rails, as we draw at full load test.

Efficiency at Low Loads

In the next tests, we measure the efficiency of HM-650 at loads much lower than 20% of its maximum rated load (the lowest load that the 80 Plus Standard measures). The loads that we dial are 40, 70 and 100W. This is important for scenarios in which a typical office PC is in idle with power saving turned on.


We expected better efficiency at low loads, since the PSU's capacity is relatively small. With 40W of load we measured under 70% efficiency and only with 100W the unit passed the 80% mark.

5VSB Efficiency

ATX spec states that the 5VSB standby supply's efficiency should be as high as possible and recommends 50% or higher efficiency with 100mA load, 60% or higher with 250mA load and 70% or higher with 1A or more load.
We will take four measurements, three at 100 / 250 / 1000 mA and one with the full load that 5VSB rail can handle.


The standby rail exhibited low efficiency overall, at least with 100mA and 250mA loads. Only in tests #3 and #4 efficiency surpassed the 70% mark.

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 (On but without any load at its rails) and the power consumption when the PSU is in standby (without any load at 5VSB).


Phantom power is under 1W so the unit is ErP Lot 6 compliant. However lately we were used to see PSUs with lower than 0.5W power consumption at standby so we were hoping for a bit better.