SilverStone SX600-G SFX Power Supply Review

Load Regulation, Hold-Up Time And Inrush Current

Test Setup

All measurements are 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 (200W). The aforementioned equipment is able to deliver 2500W of load, and all loads are controlled by custom-made software (Faganas ATE). We also use a Rigol DS2072A oscilloscope, a Picoscope 3424 oscilloscope, a Picotech TC-08 thermocouple data logger, two Fluke multimeters (289 and 175), a Keithley 2015 THD 6.5-digit bench DMM and a Yokogawa WT210 power meter. In addition, we include a wooden box, which, along with some heating elements, we used as a hot box. Moreover, we have at our disposal three more oscilloscopes (Rigol VS5042, Stingray DS1M12 and a second Picoscope 3424) and a Class 1 Brüel & Kjær 2250-L G4  Sound Analyzer, which is equipped with a type 4189 microphone that features a 16.6-140 dB(A)-weighted dynamic range. Finally, the latest addition in our testing gear is a FLIR E4 infrared camera, which, through some firmware modifications (many thanks to the fine folks at EEVblog's forums for this) is now able to deliver 320x240 resolution.

We conduct all of our tests at 40 °C to 45 °C ambient temperature to more accurately simulate the environment seen inside a typical system, with the range being derived from a standard ambient assumption of 23 °C, and 17 to 22 °C added for the typical temperature rise within a system.

Primary Rails Load Regulation

The following charts show the voltage values of the main rails, recorded over a range from 40 W to the maximum specified load, and the deviation (in percent) for the same load range.

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5VSB Regulation

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

Hold-Up Time

Hold-up time is an important PSU characteristic; it 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 the system can continue to run without shutting down or rebooting during a power interruption. The ATX specification sets the minimum hold-up time to 16ms with the 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 under-voltage threshold, or after the mains power has been removed for a sufficiently long time to guarantee that the PSU cannot operate anymore.

The registered hold-up time meets the ATX spec's requirements, although we suspected that the small bulk capacitor would pose a problem here.

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 APFC capacitor's charging current, PSUs produce large inrush current right as they are turned on. This can trip circuit breakers and fuses, and may also damage switches, relays and bridge rectifiers. As a result, the lower the inrush current of a PSU right as it is turned on, the better.

The registered inrush current is pretty low with 115 V and significantly higher at 230 V, though still on the low side.

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 percent to 105 percent of the maximum load the supply can handle, in increments of 10 percentage points.

We conducted two additional tests. In the first metric, 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 determined the maximum load the +12V rail could handle while the load on the minor rails was minimal. 

Before we start commenting on the results, we should remind you that this is an SFX-based unit, so it cannot be compared directly to standard ATX PSUs. Roomy dimensions allow for bigger components that are more suitable for higher loads. We see the +12V rail stay within two percent, a satisfactory result, while the minor rails perform decently. We would have liked the 3.3V rail to demonstrate lower than three-percent deviation, though.

With regard to efficiency, the small SilverStone supply clears the 80 PLUS Gold requirements, even though we tested at a higher ambient temperature than the 80 PLUS organization. Our most significant criticism is the excess noise that the small fan generates as it tries to keep up with heat output. We did push the SX600-G to its limits, and the outcome was definitely loud. Normally, we overload PSUs under test at 110 percent of their maximum-rated capacity. However, in this case, we noticed a prominent high-pitched noise coming out of the PSU, so we decided to perform the overload test with 105 percent load instead. It's hard to be overly picky with an SFX unit that already delivers 600W of power.