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, Rigol DS2072A oscilloscope kindly sponsored by Batronix, Picoscope 3424 oscilloscope, 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 (Rigol VS5042, Stingray DS1M12, and a second Picoscope 3424), and a Class 1 Bruel & Kjaer 2250-L G4 Sound Analyzer 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 °C - 45 °C ambient to simulate the environment seen inside a typical system more accurately, with 40 °C - 45 °C being derived from a standard ambient assumption of 23 °C and 17 °C - 22 °C being added for the typical temperature rise within a system.

To control the Chroma 6530 source, we use a GPIB-USB controller, which avoids 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, recorded over a range from 60 W to the maximum specified load, and the deviation (in percent) for the same load range.

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 a very important PSU characteristic and represents the amount of time, usually measured in milliseconds, a PSU can maintain its 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 17 ms with the maximum continuous output load.

According to the ATX spec, the PWR_OK is a "power good" signal. This signal should be asserted as high, at 5V, 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 continuous power operation within spec 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 their under-voltage threshold or when mains power has been removed for a sufficiently long time, such that the power supply's operation cannot be guaranteed. The AC loss to PWR_OK minimum hold-up time is supposed to at least be 16 ms, which is less than the hold-up time described in the paragraph above since the ATX specification also sets a PWR_OK inactive to DC loss delay which should be more than 1 ms. This means that the AC loss to PWR_OK hold-up time should always be lower than the overall hold-up time to ensures that the power supply never continues to send a power good signal while 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 might be quite low, but the power ok signal is at least accurate.

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 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, relays, and bridge rectifiers; as a result, the lower the inrush current of a PSU right as it is turned on, the better.



The absence of proper inrush-current protection leads to very high currents during the unit's start-up phase, especially when the bulk caps are discharged. If the bulk caps had the proper capacity to meet this PSU's needs, inrush current would also be significantly higher.

Load Regulation and Efficiency Measurements

The first set of tests revealed the stability of the voltage rails and the unit'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 could handle while the load on the minor rails was minimal.

Load regulation is only average when compared to high-end PSUs of similar capacity. However, none of the rails deviate by more than 2%, which is satisfactory for this price range. On top of that, efficiency is surprisingly high. We don't know how Sirfa pulled this off, but under no circumstances expected this platform to hit close to 94% efficiency with 230V, and as you can see in the table above our equipment took an impressive 93.7% reading during the fourth test. The unit also managed to deliver its full power for prolonged periods under really tough conditions. We pushed it at up to 45 °C and everything was fine.