Load Regulation, Hold-Up Time And Inrush Current
To learn more about our PSU tests and methodology, please check out How We Test Power Supply Units.
Primary Rails And 5VSB Load Regulation
Load Regulation testing is detailed here.
The following charts show the voltage values of the main rails, recorded over a range from 40W to the maximum specified load, and the deviation (in percent) for the same load range. You will also find a chart showing how the 5VSB rail deals with the load we throw at it.
Our hold-up time tests are described in detail here.
The hold-up time easily exceeded 16ms, which means a properly-sized bulk capacitor was used.
For details on our inrush current testing, please click here.
The registered inrush current was higher than other similar-capacity PSUs when tested at 115V and 230V input; however, it wasn't at dangerously high levels in any case.
Load Regulation And Efficiency Measurements
The first set of tests reveals the stability of the voltage rails and the PSU's efficiency. The applied load equals (approximately) 10 to 110 percent of the maximum load the supply can handle, in increments of 10 percentage points.
We conducted two additional tests. During the first, we stressed the two minor rails (5V and 3.3V) with a high load, while the load at +12V was only 0.10A. This test reveals whether a PSU is Haswell-ready or not. In the second test, we determined the maximum load the +12V rail could handle with minimal load on the minor rails.
|Test||12V||5V||3.3V||5VSB||Power DC/AC (W)||Efficiency (%)||Fan Speed (RPM)||Fan Noise dB(A)||TempIn/Out (°C)||PF/AC (V)|
The +12V and 5V rails offer decent, but definitely not top-notch load regulation, while the 3.3V and 5VSB rails exceeded three percent deviation. We would like to see at least the 3.3V rail staying within three percent, but obviously this platform is optimized for low budgets and not peak performance. In the efficiency section, the 550 GS easily passes the 80 PLUS Gold requirements with 20 and 50 percent load. Under full load, efficiency is 0.15 percent lower than the 87 percent we were looking for. However, as we mention in every PSU review, the 80 PLUS organization tests at 23 °C, while we conduct our tests at temperatures that reach and in many cases exceed 45 °C during the full- and over-load tests.
Due to the increased temperatures inside our hot box, ECO (passive) mode didn't have a chance to activate even during the first tests. Rather, the fan spun at low speeds up to the 30 percent load test. Afterward, it kept its noise below 40 dB(A) until the 50 percent load test, and during the last tests, the fan's output reached 46 dB(A). While we can't call this quiet, the fan's diameter is pretty small, which doesn't help in the acoustic department.