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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.

Advanced Transient Response at 20 Percent – 200ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.194V	12.057V	1.12%	Pass
5V	5.001V	4.942V	1.18%	Pass
3.3V	3.328V	3.212V	3.49%	Pass
5VSB	5.091V	5.039V	1.02%	Pass

Advanced Transient Response at 20 Percent – 20ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.187V	11.993V	1.59%	Pass
5V	5.002V	4.932V	1.40%	Pass
3.3V	3.329V	3.188V	4.24%	Pass
5VSB	5.093V	5.043V	0.98%	Pass

Advanced Transient Response at 20 Percent – 1ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.191V	11.993V	1.62%	Pass
5V	5.001V	4.929V	1.44%	Pass
3.3V	3.329V	3.191V	4.15%	Pass
5VSB	5.093V	5.036V	1.12%	Pass

Advanced Transient Response at 50 Percent – 200ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.179V	12.134V	0.37%	Pass
5V	4.993V	4.930V	1.26%	Pass
3.3V	3.325V	3.201V	3.73%	Pass
5VSB	5.055V	4.999V	1.11%	Pass

Advanced Transient Response at 50 Percent – 20ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.176V	12.104V	0.59%	Pass
5V	4.994V	4.920V	1.48%	Pass
3.3V	3.326V	3.178V	4.45%	Pass
5VSB	5.056V	4.998V	1.15%	Pass

Advanced Transient Response at 50 Percent – 1ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.178V	12.109V	0.57%	Pass
5V	4.993V	4.918V	1.50%	Pass
3.3V	3.326V	3.178V	4.45%	Pass
5VSB	5.056V	5.001V	1.09%	Pass

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During the 20 percent load test, the PSU operates in PWM mode. Hence the voltage drops once we apply the transient load are increased. This is not the case with 50 percent load where the unit operates in FM mode. The overall performance is decent, though definitely not the best. With the added caps that the ATX spec requires, the transient response is vastly improved, especially on the minor rails.

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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We notice some tiny spikes here, but they're nothing to worry about.

Ripple Measurements

Ripple represents the AC fluctuations (periodic) and noise (random) found in the PSU's DC rails. This phenomenon significantly decreases the capacitors' life span because it causes them to run hotter. A 10 degree 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	13.8 mV	6.5 mV	14.2 mV	10.6 mV	Pass
20% Load	13.6 mV	7.0 mV	14.7 mV	10.7 mV	Pass
30% Load	7.5 mV	6.6 mV	14.6 mV	10.8 mV	Pass
40% Load	7.7 mV	7.3 mV	15.9 mV	11.6 mV	Pass
50% Load	8.2 mV	7.7 mV	15.8 mV	12.7 mV	Pass
60% Load	9.3 mV	7.4 mV	15.7 mV	15.0 mV	Pass
70% Load	10.2 mV	8.4 mV	16.4 mV	16.1 mV	Pass
80% Load	11.1 mV	8.1 mV	18.4 mV	16.8 mV	Pass
90% Load	11.7 mV	8.5 mV	19.7 mV	19.4 mV	Pass
100% Load	19.2 mV	10.9 mV	21.8 mV	23.6 mV	Pass
110% Load	24.1 mV	12.5 mV	22.3 mV	25.9 mV	Pass
Crossload 1	17.6 mV	10.3 mV	21.4 mV	13.2 mV	Pass
Crossload 2	19.7 mV	8.5 mV	15.4 mV	22.0 mV	Pass

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The ripple suppression is good overall here. At 3.3V and 5VSB we measure over 20mV under full load. That's not the best performance, but far from mediocre.

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 & 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, whichcan cause problems in other close-by devices if too high.