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 components and larger heatsinks equal a better PSU.
DC Output Voltage Load Regulation
To simulate real world operation, the XClio power supply 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 under a moderately heavy load. The DC output voltages were measured with a FLUKE digital multimeter at the ATX connector.
The ATX tolerance for voltages states how much each output (rail) is allowed to fluctuate.
The following table lists the DC voltage regulation results for the XClio 750W PSU.
As you can see, all of the DC outputs were held well within the ATX specification while operating under a wide range of combined loads — very good.
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. In each case, I adjusted the O-scope time base to look for AC ripple at both low and high frequencies. The ATX 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 supplies complied with the ATX standard. The following table lists the ripple/noise results during our 263 w load test. The four main output voltages of interest (+3.3 V, +5.0 V, +12 V and +5 VSB) were recorded after the 24 hr burn-in period.
The XClio power supplies exhibited good AC ripple suppression on all of the measured outputs.
Power Factor (PF)
Power factor (PF) is one of those mysterious properties of AC that even most electrical engineers have a hard time explaining. A thorough technical discussion goes beyond the scope of this review (for a more detailed explanation please look here).
I measured the AC Power Factor with a WattsUp? Pro power analyzer. All of the XClio GreatPower power supplies incorporate active power factor correction circuits.