One of the basic measures of any ATX power supply is the unit’s overall physical weight. This may seem rather simplistic but it generally holds that more industrial grade components and larger heatsinks equal a better PSU. The following graph illustrates how the Akasa Power+ 650W PSU compares to some other popular power supplies.
(click to enlarge)
In addition to being quite heavy for a PSU in this output range the Akasa 650W PSU is also longer than the typical ATX power supply, measuring a full 180mm long — make sure your case can accommodate the extra length before you purchase one.
DC Output Voltage Load Regulation
To simulate real world operation, the Power+ PSU was connected to my home made load tester, supplied with 115 VAC, and allowed to burn-in for 24 hrs before voltage readings were taken. In this test we are interested in seeing how well a PSU can maintain the various output voltages while operating under different loads. The DC output voltages were measured with a FLUKE digital multimeter.
The new ATX12V V2.2 tolerance for voltages states how much each output (rail) is allowed to fluctuate and has tighter tolerances for the +12V1 and +12V2 outputs.
The following table lists the DC voltage results at different loads for the Akasa AK-P650FH PSU while operating on 115 VAC, 60 Hz.
The Akasa Performance+ PSU produced very good voltage regulation on all of the outputs across a broad range of loads.
AC Ripple (electrical noise) on DC Outputs
The amount of AC ripple present on the outputs was checked using an oscilloscope. This AC component may be present in the KHz range where most switching power supplies operate or it may be more prevalent at the 60 Hz line frequency. I adjusted the O-scope time base to look for AC ripple at both low and high frequencies.
The new ATX12V V2.2 specification for DC output noise/ripple is defined in the ATX12V Power Supply Design Guide.
Ideally we would like to see no AC noise on the DC outputs — the cleaner the better! But in reality there will always be some present. I measured the amplitude of the AC signal (in millivolts, peak-to-peak) to see how well the power supply complied with the ATX standard. The following table lists the ripple/noise results during our 263 w load test for the five main output voltages of interest.
The Akasa 650W power supply exhibited very good AC ripple suppression on all of the measured outputs, which was well within the ATX12V V2.2 specification.