Testing
Physical Weight
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 BFG Tech 1kW PSU compares to some other popular power supplies on the market.
(click to enlarge)
As you can see, the BFG Tech 1kW PSU falls halfway between the other two 1kW units on our chart. The overall depth of the enclosure is 175mm.
DC Output Voltage Load Regulation
To simulate real world and maximum loading conditions, the BFG 1kW PSU was connected to the load tester, supplied with 115 VAC, and allowed to burn-in for 24 hours 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 +12V outputs than the previous spec did.
The following table lists the DC voltage results at different loads for the BFG 1kW PSU while operating on 115 VAC, 60 Hz.
The BFG Tech 1kW power supply produced good voltage regulation on all of the outputs across a broad range of loads; even when delivering the maximum rated output of 1,000 watts.
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 all of the load tests for the seven main output voltages of interest.
The BFG 1kW power supply provided acceptable ripple suppression at lower power levels but by 600W, the AC ripple was high out of spec on both the +3.3V, +5V and +5VSB rails. Significant ripple was present on the +12V outputs as well but it stayed within specification. This is not good and can potentially lead to system instability.
