DC Load Regulation and AC Ripple
DC Output Load Regulation
To simulate real world and maximum loading conditions, the EVGA SuperNOVA 750 G2 and 850 G2 power supplies were connected to the load testers and supplied with a constant 115 VAC. In this test we are interested in seeing how well a PSU can maintain the various output voltages while operating under different loads.
The ATX12V V2.2 tolerance for voltages states how much each output (rail) is allowed to fluctuate and has tighter tolerances now for the +12V outputs. I have also included a second table of expanded tolerances (±1% to ±6%) for reference.
SuperNOVA 750 G2: The following tables list the DC voltage results for the 750 G2 PSU while operating on 115 VAC, 60 Hz.
The 750 G2 produced excellent voltage regulation on all of the DC outputs and all of the measured values fell easily within the 2% tight voltage regulation range that EVGA claims for their new G2 units; very good!
SuperNOVA 850 G2: The following tables list the DC voltage results for the 850 G2 PSU while operating on 115 VAC, 60 Hz.
The 850 G2 also produced outstanding voltage regulation, again staying easily within the claimed tight voltage regulation parameters of 2%.
AC Ripple and Noise on the DC Outputs
The amount of AC ripple and noise present on the DC outputs was checked using a digital 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. We adjust the O-scope time base to look for AC ripple at both low and high frequencies. The 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 ripple (repetitive) or noise (random) 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 main output voltages of interest.
SuperNOVA 750 G2:
The 750 G2 power supply exhibited excellent AC ripple suppression on all of the primary outputs, all the way up to full load.
SuperNOVA 850 G2:
The results for the 850 G2 power supply were nearly identical to the 750 G2. Again, very good!