Corsair VS650 Power Supply Review: Affordable Yet Capable

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Transient Response Tests, Ripple Measurements and EMC Pre-Compliance Testing

Advanced Transient Response Tests

For details on our transient response testing, please click here.

In the real world, power supplies are always working with loads that change. It's of immense importance, then, for the PSU to keep its rails within the ATX specification's defined ranges. The smaller the deviations, the more stable your PC will be with less stress applied to its components. 

We should note that the ATX spec requires capacitive loading during the transient rests, but in our methodology we also choose to apply a worst case scenario with no extra capacitance on the rails. 

Advanced Transient Response at 20 Percent – 200ms

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Advanced Transient Response at 20 Percent – 20ms

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Advanced Transient Response at 20 Percent – 1ms

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Advanced Transient Response at 50 Percent – 200ms

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Advanced Transient Response at 50 Percent – 20ms

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Advanced Transient Response at 50 Percent – 1ms

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The +12V rail copes pretty well with the transient loads, but the minor rails register high deviations with the 3.3V rail failing in most of the tests (without the capacitor that the ATX spec requires for these tests).

Turn-On Transient Tests

In the next set of tests, we measure the PSU's response in simpler transient load scenarios—during its power-on phase. Ideally, we don't want to see any voltage overshoots or spikes since those put a lot of stress on the DC-DC converters of installed components.

There is a notable spike at 5VSB, which stays below the corresponding limit (5.4V) though. In the +12V rail there is only a small voltage overshoot in the last test.

Ripple Measurements

Ripple represents the AC fluctuations (periodic) and noise (random) found in the PSU's DC rails. This phenomenon significantly decreases the capacitors' lifespan because it causes them to run hotter. A 10°C increase can cut into a cap's useful life by 50 percent. Ripple also plays an important role in overall system stability, especially when overclocking is involved.

The ripple limits, according to the ATX specification, are 120mV (+12V) and 50mV (5V, 3.3V, and 5VSB).

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10% Load7.1 mV8.1 mV19.2 mV13.2 mVPass
20% Load6.4 mV8.3 mV24.4 mV16.2 mVPass
30% Load8.6 mV8.9 mV24.4 mV16.8 mVPass
40% Load12.4 mV10.4 mV24.8 mV16.0 mVPass
50% Load15.1 mV12.1 mV30.0 mV19.5 mVPass
60% Load16.7 mV13.3 mV33.2 mV18.9 mVPass
70% Load18.7 mV13.4 mV33.9 mV19.7 mVPass
80% Load21.1 mV14.4 mV38.3 mV21.6 mVPass
90% Load22.4 mV16.8 mV39.6 mV23.1 mVPass
100% Load36.9 mV23.9 mV48.4 mV27.2 mVPass
110% Load41.4 mV27.1 mV48.7 mV36.4 mVPass
Crossload 114.5 mV36.5 mV31.6 mV17.0 mVPass
Crossload 239.2 mV29.5 mV40.3 mV18.1 mVPass

The ripple suppression at +12V is pretty good while at 5V and 5VSB is satisfactory. On the contrary, the 3.3V rail needs more filtering caps or a better design, since with 100% load, it is very close to the 50mV limit. Nevertheless, in the full load test we exceeded by more than 10°C the max operating temperature that Corsair mentions, and the higher the ambient the more stress to the regulation circuits hence the ripple performance deteriorates, vastly in some cases.

Ripple At Full Load

Ripple At 110-Percent Load

Ripple At Cross-Load 1

Ripple At Cross-Load 2

EMC Pre-Compliance Testing – Average & Peak EMI Detector Results

Electromagnetic Compatibility (EMC) is the ability of a device to operate properly in its environment without disrupting the proper operation of other close-by devices.

Electromagnetic Interference (EMI) stands for the electromagnetic energy a device emits, and it can cause problems in other close-by devices if too high.

The conducted EMI emissions stay low throughout the entire frequency range (150Hz - 30MHz).

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Aris Mpitziopoulos
Contributing Editor

Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.