Articles: Cases/PSU

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The above-mentioned names of power supplies are only applicable to OEM models. Boxed PSU models from FSP Group as well as from its partner brands like Zalman are based on the OEM models and the parameters and sometimes even the name of a boxed PSU may indicate quite clearly what OEM model it is based on. Thus, the table above makes it clear that the Epsilon FX700-GLN is a retail version of the FSP700-80GLN power supply (700W wattage, active PFC with an input voltage range of 90 to 265V, and a 120mm fan).

However, it would be wrong to extrapolate all the data on some boxed or OEM version of a power supply on all the other versions (obviously, one and the same model FSP700-80GLN may be ordered from FSP by some other vendor and be produced under the vendor’s own brand). These versions would have the same circuit design and, accordingly, the basic parameters, but all the external features like the coloring, length of the cables, the number and type of the power connectors are up to the particular vendor. For example, the OEM model FSP600-80GLN is sold here, in Russia, in two boxed versions: as FSP Epsilon FX600-GLN and as FSP Optima Pro OPS600-80GLN (the latter is shipped into Russia exclusively, although is represented on the global FSP Group website). These two versions are absolutely identical inside but do differ a lot externally. The Optima Pro is cheaper than the Epsilon and has fewer and shorter cables.

As I have said above, the Epsilon FX700-GLN obviously corresponds to the OEM model FSP700-80GLN. It draws on the design tradition of the BlueStorm series in its appearance, but with certain differences. The color of the case is of a somewhat different hue and looks prettier, in my opinion. The fan has changed from blue to lusterless transparent, but still hasn’t acquired highlighting.

A glance at the internals of this power supplies usually provokes a cry of surprise from a specialist as the heatsinks look far too small for the declared wattage of 700W. The heatsink with the output diode packs and the cross metal bar that is pressed – and not wholly so – to the steel side panel of the case are the only heat-spreaders to have any ribbing at all. The heatsinks of the active PFC device (the leftmost one in the picture) and of the inverter’s transistors (in the middle) are bare aluminum bars.

By the way, take note of the text on the PCB that reads: “FSP700-80GLC Main Board”. I said above that the Epsilon is a GNL model, having a 12mm fan, but there’s no inconsistency here: the GLC and GLN series use the same PCBs but differ in the configuration of the heatsinks optimized for the particular type of the fan.

Running a little ahead, I’d like to tell you this power supply had no problems working under full load continuously. Before describing the PSU’s components, I’d want to give you a couple more snapshots of its internals to better illustrate its design features. Here’s a side view:

And here’s the PCB taken out of the case:

In most “ordinary” power supplies, high-voltage output rails use large diode packs in TO-247 packaging, but the first thing to draw my attention here is that the packs on the appropriate heatsink are all Fairchild’s YM3045N (MBRP3045N) in small TO-220 packages, yet there are as many as eight in total! Closer examination shows that the packs are connected in parallel in pairs, two of them belonging to the +5V line, two more to the +3.3V line, and the remaining four to the +12V. So, there are two diode packs, each with a max current of 30A, on the +5V channel whose allowable current is 30A, too. Why this double reserve? The fact is the temperature of a diode pack depends on two factors: the passing current and the voltage drop on it (Power = I*U), but these parameters are not independent because the voltage is higher when the current is higher. Thus, the amount of power dissipated by a diode pack grows up at a faster rate than the current passing through this pack, and two packs, each of which passes a current of 15A through, dissipate less heat than one 30A pack. Talking about the specific characteristics of the YM3045N packs, it is easy to calculate that the difference in heat dissipation between these two designs is more than 30% if the current is 30A.

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