X-bit labs

Topower Power Supply Units Roundup (page 14)

Category: Other

by Oleg Artamonov

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

The PSU has four “virtual” +12V lines with a max combined load of 624W. Note the full range of supply voltages – this is the result of using active PFC.

Alas, the TOP-700P8 U14 wasn’t good under real conditions. At a load over 550W I felt the smell of overheat plastic from it. At a load of 680W and an ambient temperature of 24°C (which is much lower than a normal temperature inside a system case) it just failed after 4 minutes of operation. That’s why I don’t publish the oscillograms of the output voltage ripple – I just couldn’t make them.

The cross-load diagram shows that the PSU doesn’t have independent regulation of voltages. Moreover, even if you compare it with the above-discussed Silent Green (that has combined regulation of voltages as well), the TOP-700P8 U14 is obviously inferior. The +5V voltage goes all the way from the bottom (4.75V) to top (5.25V) limit in the diagram. As a result, the PSU can only yield a maximum of 160-170W out of the promised 220W combined on the +5V and +3.3V rails.

The reason for the failure of the PSU becomes clear when you take a look at the diagram that shows the correlation between the fan speed and the load. Starting at a modest 830rpm, the fan reaches 1350rpm under a load of 400W and that’s all. Its speed doesn’t grow up at higher loads while the temperature of the PSU continues to grow. So, it is clear that the reason for the overheat and death of the PSU was the inadequate operation of the fan speed controller.

The efficiency is in fact the single good impression about the TOP-700P8 U14. The transition to the new circuit design helped the P8 series surpass the 80% barrier at last. The PSU is 84% efficient at the maximum; its power factor is 0.98. These are much better results than those of the outdated P7 series models described above.

Anyway, this PSU didn’t impress me much. It has poor stability of the output voltages, large dimensions and a faulty fan controller that allowed the PSU to die prematurely.