Test Setup

All measurements are performed utilizing ten electronic loads (seven Array 3711A, 300W each, and three Array 3710A, 150W each), which are able to deliver over 2500W of load and are controlled by a custom made software. We also use a Picoscope 3424 oscilloscope, a CHY 502 thermometer, a Fluke 175 multimeter and an Instek GPM-8212 power meter. Furthermore, in our setup we have included a wooden box, which along with a heating element is used as a Hot Box. Finally, we have at our disposal four more oscilloscopes (Rigol 1052E and VS5042, Stingray DS1M12 and 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, if the manufacturer states that the maximum operating temperature of the test unit is only 40°C then we try to stay near this temperature, otherwise we crank up the heat inside the hotbox up to 45-50°C.

Voltage Regulation Charts

The 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 Regulation Chart

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

Efficiency Chart

In this chart you will find the efficiency of AP-550 at low loads and at loads equal to 20-100% of PSU’s maximum rated load.

Voltage Regulation and Efficiency Measurements

The first set of tests reveals the stability of voltage rails and the efficiency of AP-550. The applied load equals to (approximately) 20%, 40%, 50%, 60%, 80% and 100%, of the maximum load that the PSU can handle. In addition, we conduct two more tests. In the first we stress the two minor rails (5V & 3.3V) with a high load, while the load at +12V is only 2A and in the second test we dial the maximum load that +12V can handle while load at minor rails is minimal.

Let's start with the most impressive part first, which of course is efficiency. As you can see it is sky high even with the PSU exposed to the inferno temperatures of our hotbox. Also the PSU operated in fanless mode up to a load of 60%, so the input temperature was way higher than the output, which was measured at the front exhaust grill. For a moment I thought that the fan was defective and it wouldn't start spinning at all! Also even at full load tests, noise from the fan was minimal and barely audible. In our opinion, since the fan outputs such little noise, it would be better to be running from the start, protecting the unit's internals from high temperature, especially the caps, for which a 10°C rise of the operating temperature reduces expected lifetime by half.
Voltage regulation at +12V is tight (for our standards) while on the minor rails it's decent. At 5VSB however it is on the loose side, for those actually interested in this rail. The final verdict of these tests is this: the AP-550 is a true Platinum unit, there is absolutely no doubt about it.

Efficiency at Low Loads

In the next tests, we measure the efficiency of AP-550 at loads much lower than 20% of its maximum rated load (the lowest load that the 80 Plus Standard measures). The loads that we dial are 40, 60, 80 and 100W (for PSUs with over 500W capacity). This is important for scenarios in which a typical office PC is in idle with power saving turned on.

Efficiency at low loads is impressive to say the least! This is the first time we see a unit registering so high efficiency even with mere 40W load! Apparently no compromises have been made for this unit's efficiency/performance and Super Flower deserves a thumbs up for their design/implementation. From 80W of load and upwards the PSU is already at Platinum territories and this is nothing more than impressive!

5VSB Efficiency

ATX spec states that the 5VSB standby supply's efficiency should be as high as possible and recommends 50% or higher efficiency with 100mA load, 60% or higher with 250mA load and 70% or higher with 1A or more load.
We will take four measurements, three at 100 / 250 / 1000 mA and one with the full load that 5VSB rail can handle.

Efficiency at 5VSB is good although not ground breaking. Nevertheless in all cases it's above the respective limits and it peaks at nearly 77% with full load. Unfortunately voltage regulation on this rail isn't so great so inevitably some performance points are lost here.

Power Consumption in Idle & Standby

In the table below you will find the power consumption and the voltage values of all rails (except -12V), when the PSU is in idle mode (On but without any load at its rails) and the power consumption when the PSU is in standby (without any load at 5VSB).

Phantom power is restricted below 0.5W so this unit is compatible even with the future and stricter ErP Lot 6 2013 directive. It is good to see almost all manufacturers comply with the ErP Lot 6 directive because you can't imagine how much energy is wasted by various equipment in standby mode.