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

Advanced Transient Response Tests

For details about 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% – 200ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.161V	12.114V	0.39%	Pass
5V	5.083V	4.995V	1.73%	Pass
3.3V	3.378V	3.259V	3.52%	Pass
5VSB	5.080V	5.030V	0.98%	Pass

Advanced Transient Response at 20% – 20ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.160V	12.104V	0.46%	Pass
5V	5.083V	4.977V	2.09%	Pass
3.3V	3.375V	3.230V	4.30%	Pass
5VSB	5.082V	5.041V	0.81%	Pass

Advanced Transient Response at 20% – 1ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.160V	12.075V	0.70%	Pass
5V	5.082V	4.977V	2.07%	Pass
3.3V	3.374V	3.242V	3.91%	Pass
5VSB	5.083V	5.035V	0.94%	Pass

Advanced Transient Response at 50% – 200ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.084V	12.037V	0.39%	Pass
5V	5.062V	4.973V	1.76%	Pass
3.3V	3.360V	3.235V	3.72%	Pass
5VSB	5.046V	4.995V	1.01%	Pass

Advanced Transient Response at 50% – 20ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.084V	12.028V	0.46%	Pass
5V	5.062V	4.956V	2.09%	Pass
3.3V	3.358V	3.208V	4.47%	Pass
5VSB	5.047V	5.000V	0.93%	Pass

Advanced Transient Response at 50% – 1ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.085V	12.023V	0.51%	Pass
5V	5.062V	4.954V	2.13%	Pass
3.3V	3.357V	3.202V	4.62%	Pass
5VSB	5.048V	5.000V	0.95%	Pass

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The transient response of the +12V rail is very good. The minor rails also achieve good performance in 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.

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There is a minor spike at 5VSB which is nothing to worry about. In the second test the slope is smooth, while in the last test there is a really small voltage overshoot, which is barely noticeable.

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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Test	12V	5V	3.3V	5VSB	Pass/Fail
10% Load	12.1 mV	7.9 mV	12.1 mV	14.0 mV	Pass
20% Load	12.3 mV	9.8 mV	11.8 mV	16.0 mV	Pass
30% Load	13.0 mV	10.8 mV	12.3 mV	17.5 mV	Pass
40% Load	13.8 mV	12.3 mV	13.4 mV	17.8 mV	Pass
50% Load	14.5 mV	14.4 mV	14.2 mV	19.3 mV	Pass
60% Load	16.0 mV	15.7 mV	14.6 mV	20.4 mV	Pass
70% Load	15.9 mV	17.0 mV	15.1 mV	22.5 mV	Pass
80% Load	16.9 mV	18.9 mV	18.3 mV	25.1 mV	Pass
90% Load	30.6 mV	30.2 mV	43.8 mV	39.8 mV	Pass
100% Load	30.7 mV	30.5 mV	41.4 mV	43.3 mV	Pass
110% Load	31.6 mV	32.4 mV	42.9 mV	47.0 mV	Pass
Crossload 1	14.1 mV	19.5 mV	23.3 mV	13.5 mV	Pass
Crossload 2	27.9 mV	26.2 mV	35.9 mV	36.4 mV	Pass

The ripple suppression is good at +12V, satisfactory at 5V and mediocre on the other two rails.

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Ripple At Full Load

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Ripple At 110-Percent Load

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Ripple At Cross-Load 1

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Ripple At Cross-Load 2

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EMC Pre-Compliance Testing – Average and 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. For example, it can be the cause of increased static noise in your headphones or/and speakers.