Test Setup

All measurements were performed using two Chroma 6314A mainframes equipped with the following electronic loads: six 63123A [350 W each], one 63102A [100 W x2], and one 63101A [200 W]. The aforementioned equipment is able to deliver 2500 W of load, and all loads are controlled by a custom-made software. The AC source is a Chroma 6530 capable of delivering up to 3 kW of power. We also used a Keysight DSOX3024A oscilloscope, a Rigol DS2072A oscilloscope kindly sponsored by Batronix, a Picoscope 3424 oscilloscope, a Picotech TC-08 thermocouple data logger, two Fluke multimeters (models 289 and 175), a Keithley 2015 THD 6.5 digit bench DMM, and a lab-grade N4L PPA1530 3-phase power analyzer along with a Yokogawa WT210 power meter. We also included a wooden box, which, along with some heating elements, was used as a hot box. Finally, we had at our disposal three more oscilloscopes (a Rigol VS5042, a Stingray DS1M12, and a second Picoscope 3424), and a Class 1 Bruel & Kjaer 2250-L G4 Sound Analyzer we equipped with a type 4189 microphone that features a 16.6-140 dBA-weighted dynamic range. You will find more details about our equipment and the review methodology we follow in this article. We also conduct all of our tests at 40-45 °C ambient to simulate the environment seen inside a typical system more accurately, with 40-45 °C being derived from a standard ambient assumption of 23 °C and 17-22 °C being added for the typical temperature rise within a system.

We use a GPIB-USB controller to control the Chroma 6530, which avoid its very picky Serial port. This controller was kindly provided by Prologix.



We use an OLS3000E online UPS with a capacity of 3000VA/2700W to protect our very expensive Chroma AC source.

Primary Rails Load Regulation

The following charts show the voltage values of the main rails and include the deviation (in percent) for the same load range. These voltage values start at 60 W and go to the maximum specified load.

5VSB Regulation

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

Hold-up Time

Hold-up time is a very important PSU characteristic and represents the amount of time, usually measured in milliseconds, a PSU can maintain output regulations as defined by the ATX specification without input power. In other words, it is the amount of time a system can continue to run without shutting down or rebooting during a power interruption. The ATX specification sets the minimum hold-up time with the maximum continuous output load to 17 ms.

According to the ATX specification, PWR_OK is a "power good" signal. This signal should be asserted as high on the 5V rail by the power supply to indicate that the +12V, 5V, and 3.3V outputs are within the regulation thresholds and that sufficient mains energy is stored by the APFC converter to guarantee a system's continuous operation for at least 17 ms. Conversely, PWR_OK should be de-asserted to a low state, 0V, when any of the +12V, 5V, or 3.3V output voltages fall below the under-voltage threshold or when mains power has been removed for long enough to guarantee that a power supply isn't operating anymore. The AC loss to PWR_OK minimum hold-up time is set to 16 ms, which is less than the hold-up time described above, but the ATX specification also sets a PWR_OK inactive-to-DC loss delay that should be higher than 1 ms. This means that the AC loss to PWR_OK hold-up time should be lower than the PSU's overall hold-up time to ensure that the power supply doesn't send a power good signal once any of the +12V, 5V and 3.3V rails are out of spec.

In the following screenshots, the blue line is the mains signal, the green line is the "Power Good" signal, and the yellow line represents the +12V rail.







Hold-up time was below 17ms, which had the V650 fail this test. To make things worse, the power good signal dropped after and not before the rails went out of spec. This means that although the rails aren't within the ATX specification's range, the PSU reports that its voltage outputs are normal, which can affect a system's proper operation and, as such, its reliability.

Inrush Current

Inrush current, or switch-on surge, refers to the maximum, instantaneous input-current drawn by an electrical device when it is first turned on. Because of the charging current of APFC capacitor(s), PSUs produce a lot of inrush-current right as they are turned on. A lot of inrush current can cause the tripping of circuit breakers and fuses and may also damage switches, relays, and bridge rectifiers; as a result, the lower a PSU's inrush current right as it is turned on, the better.



Inrush current is pretty high since it exceeds 50 A.

Load Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the V650's efficiency. The applied load was equal to (approximately) 10%-110% of the maximum load the PSU can handle, in 10% steps.

We conducted two additional tests. In the first test, we stressed the two minor rails (5V and 3.3V) with a high load while the load at +12V was only 0.10 A. This test reveals whether the PSU is Haswell ready or not. In the second test, we dialed the maximum load the +12V rail can handle while the load on the minor rails is minimal.


Load regulation isn't very tight at 3.3V since it deviated by 3.62%. Efficiency is pretty high, and the fan proved to be quiet enough at even full speed, which had it spin at 2300 RPM. The fan's profile is clearly tuned for lower ambient temperatures, though, which had the fan's noise output increase significantly once the PSU had been pushed.

We would like to see tighter voltage regulation in these tests, along with over 90% efficiency in the 20% load test. Lower fan speeds at higher loads would also result in less noise output without compromising this PSU's reliability.