DC Load Regulation and AC Ripple
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 Corsair HX850 Platinum 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 cables/connectors were used to connect the Corsair HX850 PSU to the PCPerspective power supply test equipment.
• (1) 20+4 pin ATX
• (2) 8-pin EPS/ATX12V
• (6) 6-pin PCI-E
• (6) SATA
• (3) Molex
DC Output Load Regulation
To simulate demanding and maximum loading conditions, the Corsair HX850 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 HX850 PSU while operating on 120 VAC, 60 Hz.
The Corsair HX850 PSU produced excellent voltage regulation on all of the DC outputs. The three main outputs stayed within ±2% of the recommended guidelines; very good!
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 HX850 power supply did an excellent job of keeping the AC ripple and noise well under control. Note how low the +12V output stayed, even at full load.
PSU reviews are immensely
PSU reviews are immensely boring.
While the number of
While the number of spectacular PSU failures has markedly decreased, reviews such as this excellent example are incredibly important when making purchasing decisions. Have a little respect for the work that Lee has put into this review.
Maybe reviewers could spice
Maybe reviewers could spice up the format by testing PSUs to the point of failure. I would like to see what it takes to physically destroy these things. Can one take a 850W PSU to 1000W? What happens if I short an active power cable? What happens to thermals without the fan active? Can I add a waterblock to it in a custom cooling loop? There are so many interesting questions.
Virtually all enthusiast
Virtually all enthusiast grade PSUs have built in safety circuits that are designed to protect the PSU from catastrophic failure. I have only had one PSU actually explode (fireball, sparks and smoke) during testing over the last fifteen years. Over Current protection or Over Power protection should shut the PSU down if too heavy a load is applied to a particular rail or the total output power is exceeded. Short circuit protection should shut it down if a short occurs on one of the outputs. And if the cooling fan fails, Over Temperature protection should shut the PSU down before it self destructs. Boring but safe!
And water-cooling a PSU is possible (although maybe not practical). I have done this in the past by attaching several custom made water blocks to the PSU's existing aluminum heat sinks. I chose a PSU that was designed to operate fanless, removed the cover and attached three custom water blocks. Use your imagination… 🙂
Maybe I missed it but I read
Maybe I missed it but I read through the review and didn’t see any info about what the 12v real switch actually does other then switching between single rail and multi rail mode.
Does this have any impact at all on the operation? Is effeciency affected? What kind of scenarios exist in which that feature is even useful? I can’t really think of one, although I’m not a die-hard PSU junkie.