DC Load Regulation and AC Ripple
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
• Differential Temperature
The Seasonic FOCUS PLUS 650W Gold 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 (+12V1, +12V2, +12V3, and +12V4)
• (2) 200W Precision resistor load bank (+12V5 and +12V6)
• 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)
• Extech Model 407738 digital sound level meter (Accuracy ±1.5 dB)
The following connectors were used to attach the FOCUS PLUS PSU to the PCPerspective power supply test equipment.
• (1) 20+4 pin ATX
• (1) 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 FOCUS PLUS 650W Gold power supply was connected to the load testers and supplied with 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 Seasonic FOCUS PLUS 650W Gold PSU while operating on 120 VAC, 60 Hz.
The voltage regulation was excellent, staying within ±1% of the recommended ATX guidelines for the three main outputs and complying with Seasonic’s own Micro Tolerance Load Regulation claims.
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 FOCUS PLUS 650W Gold power supply also exhibited very good AC ripple and noise suppression across the full range of loads.
Good read – and good to see
Good read – and good to see Seasonic on top of their game yet. I’m due for a new build soon and this looks like a really good option.
My main gaming PC is running a 10 year old Seasonic M12 SS-600HM and it’s still going strong through a couple board/CPU upgrades and multiple graphics card upgrades.
It is good that PSU
It is good that PSU manufacturers understand that the 230 mm power supplies of half a decade ago are not really needed anymore. Sure, it may look cool to some because they believe bigger to be better, but a short power supply for anything under a kilowatt is just fine given proper design.
I just need a reason to
I just need a reason to change my 7 year old seasonic that is serving its 3rd build.. But am feeling guilty of replacing a perfectly good, reliable and working PSU that has no problems.. Damn you Seasonic.
Well done Seasonic-you set
Well done Seasonic-you set the standards by which
others are measured…………
The box art is making me
The box art is making me hungry for chips.
This PSU seems to be of
This PSU seems to be of insane value as it is smaller, better AND cheaper then the Corsiar RM650x!
“our PSU was delivered
“our PSU was delivered straight from Newegg.com inventory.” On front page yet last page says “Our thanks to Seasonic for sending us the FOCUS PLUS 650W Gold PSU to review!” Guess they are getting the cherry picked samples.
It ordered by Seasonic from
It ordered by Seasonic from reseller’s stock… Good job Sherlock to find out nothing… 😉
650RM vs 650FX, 650RM “old
650RM vs 650FX, 650RM “old model” is better than the “new” 650FX
the old had more available cables such as 4+4 attached for cpu power and an extra 1×8 12v for cpu as well, this way here you did not need buy a higher wattage PSU that you will not need for nothing.
some builds that you may have an extra powerful cpu you may not have need of an extra power gpu, but even than, 450w of power is quite a bit of juice for even a very high end core i7 overclocked as well as pretty much any modern AMD or Nvidia graphics card (single one at least) in an overclocked state, so 54a 12v is plenty really, this saves you from having to buy an adapter for the extra cpu power (which quite a few motherboards are now using)
Seasonic is top quality bar none, but, it seems they took a hit on functionality “upgrading” from the semi-modular 650RM to the full modular 650FX, not quite as much in the 3v or 5v rails as well as a few cable change but also costing on average a little bit more $.
glad I bought the 650RM….as well, the cables that are not modular 99% of the time you will be using them anyways ^.^
Hello, do you have maybe
Hello, do you have maybe cab;e pinout for focus plus series?
Hey guys should i put into PSU another 8pin cable for my new 3080 OR it will be enough if I stick with one that’s is connected to my 1060 (it has another 8pin plug)
Technically just one cable is enough to support both 8-pin connectors, but I like to use two separate cables when possible. The 3080 is capable of pulling quite a bit over 320 W in instantaneous bursts.
Thanks fo the reply 🙂 i will pług second cable for platform stability 🙂
And one more quick question in second PC i will probably install 3070 (unit with same seasonic psu) in that rig one cable should be totally ok