The first series of power supply units we are going to examine is three models, available in our lab: PUREPOWER680-APD and TWV-480AD from well-known Thermaltake as well as FSP550-60PLN from FSP Group.

Running a few steps forward, I'd like to note that I'm not yet planning on publishing a lot of PSU photos in the exploded form in the nearest future — in some cases components are so tightly packed on a PCB that it's rather hard to make out the innards on a close-up, because of the heatsinks on key transistors, for example. Nevertheless, I'm not going to renounce such photos either.

Exterior, bundle

Both Thermaltake models come shipped in traditionally bright boxes, literally covered with icons, which may help a person to get a general idea of PSU parameters even without the English knowledge. Let's start with a junior model, TWV-480AD. The case of this power supply is made of matt black metal (painted), which contrasts with the orange plastic of two 80-mm fans. Besides the traditional user's manual, the bundle includes a 20-24 pin power adapter, an additional 80-mm fan, a power cord, and a fan control panel to be installed into the 5.25-inch drive bay. Besides two rpm controls, the control panel houses a three-section display that shows the current power consumption of the system.

PUREPOWER680-APD is another power supply unit in a mirror case (black color). Like the junior model, this supply unit is equipped with two 80-mm fans (a fan on the rear panel and a fan on the bottom that drives the air in). The bundle includes a traditional power cord, user's manual, and a 20-24 pin power adapter.

We got the FSP550-60PLN unit as part of a stand-alone solution, so unfortunately we cannot say anything about its bundle or package (if it had any). The unit itself has a regular case of a metal color, it's equipped with a single 80-mm fan. Judging from the type and number of connectors, this PSU does not pretend to be a server power supply — especially as such PSUs are sure to have additional requirements, like a hot swap feature.

Connectors

To all appearances, the manufacturer positions the PUREPOWER680-APD as a server PSU — the increased number of power connectors corroborates to it. Note that this model has two power connectors for PCI Express video cards - so this PSU can be used in graphics workstations as well; the other two PSUs are intended rather for regular but powerful enough systems:

Before we analyze the stability of output voltage in the power supply units and their pulsations in the main (+12 and +5 V) power buses, we'd like to dwell on a couple of issues. Let's have a look at the oscilloscope specifications first:

All the measurements were taken with the standard TP6060 probes. Secondly, we should note the oscillogram display types. This device provides two modes: dots and vectors. Of course, the vector display mode seriously increases the number of displayed interferences, while they are not to be seen in the dot display mode (you can see only peak dots). We'll publish diagrams both in dots and vectors where necessary. Taking into account our readers' comments to the first articles about PSUs, in some cases we took additional oscillograms for improved accuracy to detect real non-random interferences. On all the diagrams published below CH1 - +12 V, CH2 - +5 V, the division ratio of a probe is 1:1.

The load error (in the voltage metering mode) is from 0.05 to 0.1%, the output is mean results for 200ms.

Purepower 680-APD

In this case pulsations in both buses (+5 and +12 V) turn out significant. Moreover, +5 V pulsations considerably pass the limits mentioned in PSDG - 10%. Voltage stability test results: the minimum measured value on the +12 V bus is +11.78, and the maximum value is +12.18 V. The minimum value on the +5 V bus is +4.78, maximum — +5.16 V, +3.3 V bus — +3.16 and +3.30 V correspondingly.

Purepower TWV-480AD

+12 V bus pulsations are about 20.8 mV, +5 V bus - max. 16.8 mV. Voltage stability test results: the minimum measured value on the +12 V bus is +11.45, and the maximum value is +12.20 V. The minimum value on the +5 V bus is +4.80, maximum — +5.14 V, +3.3 V bus — +3.18 and +3.40 V correspondingly.

FSP550-60PLN

+12 V bus pulsations are about 46.4 mV, +5 V bus - max. 24.8 mV. Voltage stability test results: the minimum measured value on the +12 V bus is +11.58, and the maximum value is +12.15 V. The minimum value on the +5 V bus is +4.79, maximum — +5.15 V, +3.3 V bus — +3.22 and +3.44 V correspondingly.

Conclusions

The reviewed power supply units seem rather stable, none of them violated the voltage tolerances recommended by PSDG. But Purepower 680-APD perplexed us with its pulsations, even additional readouts didn't improve the situation, +5 V bus pulsations always exceeded the 10% limit, specified in PSDG. Probably, these results (PSUs in general) may be governed by the load applied during the test (1) being much lower than the officially claimed one, and (2) corresponding to the relatively abstract values, suggested by the Power Supply Design Guide (we used the loads, recommended for measuring the efficiency of 400W PSUs according to the PSDG table). As this document lacks any rough values for PSUs above 400 W, we probably should review the power supply load options in order to obtain more or less trustworthy data, which would allow to evaluate the PSU quality compared to other models. The current method initially puts PSUs of different power capacity into unequal conditions - say, 460 and 550 W PSUs are loaded as an abstract 400W model.

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