X-bit labs

ATX Power Supply Units Roundup. Part VII (page 11)

Category: Other

by Oleg Artamonov

[ 09/04/2007 | 10:40 AM ]

Alas, the cross-load diagram for the 700W model looks bad. The +5V voltage drops quickly as the load on the corresponding rail is increasing. As a result, it goes below the allowable minimum at a load much smaller than declared (about 130W for the +5V and +3.3V combined, the declared maximum being 155W).

It’s even worse with the higher-wattage models. The 800W model has a too high +12V voltage (see the red color in the left of the diagram). Both PSUs went out of the allowable range for the +5V voltage even sooner than the Epsilon 700 did. Of course, modern PCs do not load the +5V rail much, but when the manufacturer promises up to 175W, you expect to have 175W, not only half that wattage, even if you’ll never need that much.

FSP Epsilon 700

At full load the output voltage ripple was at the limit (50 millivolts) on the 700W model’s +5V and +3.3V rails.

FSP Epsilon 800

This limit is exceeded by the Epsilon 800: 60 millivolts on the +5V rail and 100 millivolts on the +3.3V rail.

FSP Epsilon 900

The picture is different with the senior model: the pulsation is a little higher than the allowable 50 millivolts on the +5V and +3.3V rails but there are short spikes on the +12V rail. With those spikes the pulsation is as high as 120-150 millivolts on the +12V rail, the allowable maximum being 120 millivolts.

Thus, the Epsilon 700 is the only PSU out of the three that complies with the requirements of the Power Supply Design Guide in terms of output voltage ripple at full load.