DC Load Regulation and AC Ripple
PSU Testing Methodology
Establishing an accurate load is critical to testing and evaluating a PC power supply. PCPerspective’s power supply test bench can place a precise DC load on the PSU under test. Each power supply is tested under controlled, demanding conditions up to its maximum rated load (at 40ºC). Our current suite of tests includes:
• DC Load Regulation
• AC Ripple and Noise
• Efficiency
• Differential Temperature
• Noise
The Seasonic PRIME Ultra 750W Titanium power supply was evaluated on both features and performance. A full range of equipment was used to test the power supply under controlled load conditions.
• (2) CSI3710A Programmable DC load (+3.3V and +5V outputs)
• (4) CSI3711A Programmable DC load (+12V)
• (3) 218W Precision resistor load bank (+12V)
• Switchable precision resistor load bank (-12V and +5VSB)
• Agilent 34401A digital multimeter (Accuracy ±0.0035% vDC)
• Extech 380803 Power Analyzer (Accuracy ±0.5% of full scale)
• DS1M12 "StingRay" digital oscilloscope (20M S/s with 12 Bit ADC)
• Powerstat Variable Autotransformer, 1.4 KVA, 0-140 VAC
• Extech Model 407738 digital sound level meter (Accuracy ±1.5 dB)
The following cables/connectors were used to connect the Prime Ultra 750W power supply to the PCPerspective power supply test equipment.
• (1) 20+4 pin ATX
• (2) 8-pin EPS/ATX12V
• (4) 6-pin PCI-E
• (6) SATA
• (3) Molex
DC Output Load Regulation
To simulate demanding and maximum loading conditions, the power supply was connected to the load testers and supplied with a constant 120 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.
The following tables list the DC voltage results for the PSU while operating on 120 VAC, 60 Hz.
The PRIME Ultra 750W Titanium power supply produced outstanding voltage regulation on all of the DC outputs while delivering the full rated 750 watts total load. All of the primary rails stayed within the claimed 0.5% load regulation and the all-important +12V output only dropped 0.03V. Awesome!
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.
The PRIME Ultra 750W Titanium power supply exhibited outstanding AC ripple and noise suppression across the full range of loads and stayed well below the claimed 20mV p-p.
I just wonder how are you
I just wonder how are you going to clean, while still keeping it under warranty, something that has a 12 year warranty.
I have an original Prime 650
I have an original Prime 650 (not Ultra) and would like to know specifically how they differ.
It would seem the Ultra is just a Prime, with a couple of meaningless upgrades. Is this true?
Yes, as we said above, the
Yes, as we said above, the Ultra is an upgraded PRIME. Along with some minor tweaks to the design (Seasonic does not specify exactly what) the main difference is the longer 12-year warranty – I wouldn't call that meaningless. If you have an original PRIME you should be well served for many years to come.
They did specify it, when
They did specify it, when they released upgraded Ultra line. See:
https://seasonic.com/news/post/prime-ultra-power-supplies/
Are the PSUs really that
Are the PSUs really that quiet? Basically not audible, quieter than the room? My computer’s fan go at 450RPM and I have no HDDs to make spinning noises anymore.
Yes, they are very quiet. But
Yes, they are very quiet. But sound/noise is subjective. Even though the SPL numbers are hard data different people respond differently to sound. To my ears, this PSU was very quiet – silent until the fan kicked in (no coil whine or electro-mechanical noise). The test lab is relatively cool and quiet (fairly constant 73 deg and 27 dBA) – to the point I opt to turn off the building A/C air handler during testing. Both the background temp and sound level will contribute to your experience of how loud a system is. Hope that helps answer your question.