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 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 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
• (2) SATA
• (2) 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 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 0.02V. Very impressive!
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 750W Titanium power supply exhibited outstanding AC ripple and noise suppression across the full range of loads.
I’m a little concerned about
I’m a little concerned about the switch from Sanyo Denki fans to Hong Hua, but given that warranty, it seems that Seasonic is confident that the fans will last.
If it’s anyhting like their
If it’s anyhting like their previous PSUs, the fan never spins anyway if you size it slightly bigger than your needs.
Just bought an X850 Gold dirt
Just bought an X850 Gold dirt cheap on Newegg and it has the Sanyo Denki fan.
I’ve been hoping you guys
I’ve been hoping you guys would review this PSU. Good job!
How about coil whine? It will
How about coil whine? It will not show up in normal sound pressure measurements. Did you notice any coil whine?
I had extreme trouble finding a power supply without bad coil whine. I went through several very expensive and recognized brands before settling on the Corsair RM750.
Neither of my Seasonic X
Neither of my Seasonic X Series have coil whine and i am EXTREMELY sensitive to it. My ears fill with fluid sometimes as the result of a back and neck injury, so coil whine(or any high frequency sounds) actually cause me physical pain 🙂
From what i read, this Seasonic will not have coil whine since its coils are encased in something specifically to prevent vibration.
Seasonic or something they
Seasonic or something they have created for OEM is the only power supplies I buy, but usually they have a really understated design, a shame they have gone away from that, this is starting to remind me of something “gaming” branded!
i’m using Seasonic X-750
i’m using Seasonic X-750 (KM3) but frankly speaking, Seasonic had the highest & the worst failure rate ever.
Wheres the data?
Wheres the data?
I had a X-series 750 blow a
I had a X-series 750 blow a cap. but they replaced it really quick. Excellent Customer Service
https://www.techpowerup.com/f
https://www.techpowerup.com/forums/threads/quality-seasonic-psu-kicks-the-bucket-early.213005/
http://www.hardware.fr/articles/947-6/disques-durs.html
dude, google is your friend. please don’t denied that Seasonic higher failure rate.
by the way, i’m Seasonic fan-boy.
650W versions apparently got
650W versions apparently got delayed because the cables had issues/defects during tests on a Chroma station.
Hence why only reviews of the 750W one are showing up for now.
I would like to see a review
I would like to see a review of the Seasonic Prime 1000W Platinum PSU once it’s available.