AC Ripple and Power Factor
AC Ripple and Noise on the DC Outputs
The amount of AC ripple and noise present on the DC outputs was checked using an 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. I adjusted the O-scope time base to look for AC ripple at both low and high frequencies.
The new 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 Corsair AX1200i Digital power supply exhibited excellent AC ripple suppression across the entire load range, even when delivering 1,200W; very clean.
Power Factor (PF)
Power factor is defined as the ratio of true power (measured in watts) to apparent power (measured in Volt Amps). It measures how effectively AC power is being used by a device. The difference between true power and apparent power is expressed as the power factor and results from the way true power and apparent power are measured. Ideally we would like to have true power and apparent power equal to one another, which would result in a PF of 1.00 or 100% effective power utilization.
AC Volts x AC Amps = VA (Volt Amp)
Purely Resistive AC Load: VA = Watts (same as DC circuits)
Inductive/Reactive AC Load: VA x PF = Watts
AC Volts x AC Amps x PF = Watts
I measured the AC Power Factor with an Extech power analyzer at both 115 VAC and 240 VAC input voltages. The AX1200i power supply uses Active PFC circuits so as expected; the majority of readings were at or close to 1.0 at the higher loads.
Note: A power supply with active PFC is more environmentally friendly (doesn’t pollute the AC transmission grid with harmonics) and will draw less current, but it will not save you money on your monthly electric bill unless you are a commercial user whose bill is based on PF and usage.
Lee and or PCPER I am a bit
Lee and or PCPER I am a bit confused about the PSU test bench as described in this article. ‘Up to 2000W’ but also mention real-world test.
Which tests are you using the PC-based load for and which tests are you using simulated loads for ?
Or are you using both?
Many of the top review sites are using the imported ATX tester or home brew resistor grids which is not a ‘real world test’ (but a simulated one) and I am interested as to how you are pulling off a real world PSU test
Additionally, testing in open air versus mounted in a warm PC chassis, typically pushed against a wall or under a desk.
Thanks.
The PCPerspective PSU test
The PCPerspective PSU test bench uses a combination of six Progammable DC loads and up to three different banks of precision load resistors to create the various loads (up to 2,000W max). The real-world testing is stated because we mount each PSU in a modified case and recirculate some of the warm exhaust air back to the inlet to "simulate" real-world operating conditions. The loads are not real-world (actually much more precise and programmable) but the test environment is, temps gradually increase as the load increases just like in a real PC – the best of both worlds.
Hi I’m Carlos , I have a
Hi I’m Carlos , I have a Corsair AX1200.
ME DAMAGE IS A POWER SUPPLY CAPACITOR , THE POWER SUPPLY NOT OPERATE MORE. I’M FROM ARGETINA AND I CAN NOT GET THE CAPACITOR (2.2uf 450V) FROM THE +5VSB PCB. HOW CAN I FIX THE `POWER SUPPLY???
There is a led on the dongle
There is a led on the dongle that flashes between red and green, what is its meaning?
Thanks