DC Load Regulation

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

All three of the Seasonic PRIME Titanium Series power supplies were 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 Titanium power supplies to the PCPerspective power supply test equipment.
•    (1) 20+4 pin ATX
•    (2) 8-pin EPS/ATX12V
•    (4) 6-pin PCI-E (650W and 750W), (6) 6-pin PCI-E for the 850W
•    (6) SATA
•    (6) 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 three PSUs while operating on 120 VAC, 60 Hz.

Seasonic PRIME 650W Titanium PSU


Seasonic PRIME 750W Titanium PSU


Seasonic PRIME 850W Titanium PSU

All three PRIME Titanium power supplies produced outstanding voltage regulation on all of the DC outputs while delivering the full rated load. And the three primary rails stayed within the claimed 0.5% load regulation!

What really impressed us however is how close the numbers are from one power supply to another. This is a very good indicator of high quality.

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