X-bit labs

Topower Power Supply Units Roundup (page 12)

Category: Other

by Oleg Artamonov

[ 11/07/2007 | 11:31 AM ]

The 700W unit boasts an excellent quality of regulation. None of the three tracked voltages deflects by more than 2% from the nominal value.

The output voltages of the senior model are somewhat less stable due to unclear reasons (the two PSUs have an identical circuit design). Anyway, none of the voltages violates the allowable limits at any permissible load on the PSU.

TOP-700P7 SEZ

TOP-750P7 FEZ

The oscillograms of the output voltage ripple show a familiar picture. Both PSUs are close to the allowable maximum of 50 millivolts (1 division of the vertical axis) on the +5V rail and even exceed it during individual spikes.

The PSUs are cooled with couples of Sanyo Denki "San Cooler 80" fans (9A0812H401 model, 80x80x25mm form-factor).

Their speed is constant (about 1500rpm) at loads below 200W. Then it grows up linearly to reach a maximum of 2700rpm. Despite the smaller fan speed in comparison with the above-discussed TOP-700P7 FR, the temperature of air was lower at the output. That’s an interesting thing, probably resulting from the use of different fans. Neither the TOP-750P7 FEZ nor the TOP-700P7 SEZ had overheat-related problems.

Alas, these PSUs have an efficiency of only 77%. The power factor is 0.7 (the PSUs don’t have any kind of power factor correction notwithstanding the pretty pictures on the boxes).

So, the SEZ and FEZ models of the P7 series are versions of the FR models with detachable cables. Alas, this is the single good point of their design. The cables themselves are impractical. It is going to be difficult to lay them properly in a small and even medium system case. Moreover, with their high stiffness they are going to mechanically stress the connector of the powered device (I can remember IBM’s ICL35 series HDDs in which a permanent stress on the power connector would often lead to a loss of contact between the hermetic block and the electronics card, and the HDD would just fail as the consequence). Very high stability of the output voltages is the only notable thing about the electrical parameters of these PSUs.