Test SetupAll 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. We also used a Picoscope 3424 oscilloscope, a Picotech TC-08 thermocouple data logger, a Fluke 175 multimeter, and 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 four more oscilloscopes (Rigol 1052E and VS5042, Stingray DS1M12, 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, we conduct all of our tests at 40 - 45°C ambient in order to simulate with higher accuracy the environment seen inside a typical system, 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.
Primary Rails Voltage RegulationThe following charts show the voltage values of the main rails, recorded over a range from 60W to the maximum specified load, and the deviation (in percent) for the same load range.
5VSB RegulationThe following chart shows how the 5VSB rail deals with the load we throw at it.
Hold-up TimeThe hold-up time is a very important characteristic of a PSU and represents the amount of time, usually measured in milliseconds, that a PSU can maintain output regulations, as defined by the ATX spec, without input power. In other words, it is the amount of time that the system can continue to run without shutting down or rebooting during a power interruption. The ATX spec sets the minimum hold-up time to 16 ms at maximum continuous output load. In the following screenshot, the blue line is the mains signal and the yellow line is the "Power Good" signal. The latter is de-asserted to a low state when any of the +12V, 5V, or 3.3V output voltages fall below the undervoltage threshold, or after the mains power has been removed for a sufficiently long time to guarantee that the PSU cannot operate anymore.
The hold-up time is way above the minimum allowed time with 19.8 ms, and the AX760 easily takes the first place in the above graph.
Inrush CurrentInrush current or switch-on surge refers to the maximum, instantaneous input-current drawn by an electrical device when first turned on. Because of the charging current of the APFC capacitor(s), PSUs produce large inrush-current right as they are turned on. Large inrush current can cause the tripping of circuit breakers and fuses and may also damage switches or relays; as a result, the lower the inrush current of a PSU right as they are turned on, the better.
The AX760 registered significantly higher inrush current than its AX760i cousin, but 37.52 A won't cause any long term issues since inrush current under 40 A is restricted.
Voltage Regulation and Efficiency MeasurementsThe first set of tests revealed the stability of the voltage rails and the efficiency of the AX760. The applied load was equal to (approximately) 20%, 40%, 50%, 60%, 80%, 100% and 110% 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 (5V and 3.3V) with a high load while the load at +12V was only 2 A, and, in the second test, we dialed the maximum load that the +12V rail could handle while the load on the minor rails was minimal.
| Voltage Regulation & Efficiency Testing Data |
|Test||12 V||5 V||3.3 V||5VSB||Power|
|20% Load||10.751A||1.981A||1.974A||0.984A||151.72W||92.59%||0 RPM||49.87°C||0.920|
|40% Load||21.884A||3.968A||3.952A||1.186A||303.68W||93.67%||0 RPM||51.33°C||0.966|
|50% Load||27.344A||4.966A||4.943A||1.584A||379.67W||93.47%||864 RPM||41.47°C||0.974|
|60% Load||32.803A||5.967A||5.935A||1.985A||455.55W||93.24%||1760 RPM||42.43°C||0.980|
|80% Load||43.927A||7.960A||7.924A||2.395A||607.43W||92.60%||1940 RPM||43.26°C||0.985|
|100% Load||55.690A||8.967A||8.923A||3.010A||759.34W||91.85%||1970 RPM||44.86°C||0.987|
|110% Load||62.048A||8.970A||8.929A||3.014A||835.24W||91.59%||1980 RPM||44.96°C||0.987|
|Crossload 1||1.966A||15.004A||15.005A||0.502A||151.71W||86.74%||1655 RPM||43.74°C||0.926|
|Crossload 2||62.965A||1.000A||1.003A||1.002A||770.75W||92.47%||1970 RPM||44.93°C||0.987|
Efficiency is out of this world and Seasonic managed to prove that they can match the performance of the AX760i without digital control. The PSU performed amazingly well at the high ambient we conducted all of the above tests in. Voltage regulation on the +12V rail was very good, although it cannot compete its AX760i cousin, but the AX760 did take the lead on the minor rails! Also, the fan did not spin up at all until a 40% load was reached and that with the high ambient inside the hotbox. The fan spun at low RPM with a 50% load, and increased its speed dramatically, leading to high noise output, at loads above 50%.