X-bit labs

Topower Power Supply Units Roundup (page 5)

Category: Other

by Oleg Artamonov

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

Featuring dedicated voltage regulation, the PSU delivers very stable voltages just as you may have expected. None of the three tracked voltages gets close to the maximum allowable deflection of 5% from the nominal value at any load.

There are problems with the output voltage ripple, though. At maximum load the +5V oscillogram shows spikes that are somewhat higher than the 50 millivolts permitted by the standard. The manufacturer should have used better electrolytic capacitors on the output or shunt them with additional ceramic capacitors.

There is low-frequency pulsation, too. It is quite strong on the +12V rail although never goes beyond the allowable maximum of 120 millivolts.

The PSU is cooled with a 120x120x25mm fan (Globe Fan S1202512M).

The fan speed is constant at loads below 350W. After that it grows up linearly, but not too fast. If the initial speed were lower, the TOP-500P7 U12 might be called a quiet PSU. At 1100rpm it is only average in terms of noisiness. The temperature increase inside the PSU is quite high, by the way.

I guess there are two reasons for the temperature to increase so much despite the not-very-slow fan: a rather low efficiency and a high component density of the PCB (contrary to the common opinion, heatsinks with a lot of narrow ribs are not very efficient because they provide a high resistance to air flow; you can note that the quiet PSUs from Seasonic, Corsair and Zalman have heatsinks of a simpler shape than the ones employed in the TOP-500P7).

The efficiency is constant through a large range of loads but is only 76% at the maximum. That’s a very modest result for a modern PSU. The power factor is not high due to the lack of any type of correction.

So, the TOP-500P7 U12 is a regular mainstream PSU. None of its parameters is exceptional, and its circuit design is somewhat outdated. The PSU even didn’t meet the requirements of ATX12V Power Supply Design Guide in terms of output voltage ripple, even though by just a little. The increased length of the case is a drawback, too. The PSU of this wattage might have been designed within a standard-size case.