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Transient Response Tests, Timing 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 additional capacitance on the rails.

Advanced Transient Response at 20% – 200ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.100V	11.995V	0.87%	Pass
5V	4.997V	4.878V	2.38%	Pass
3.3V	3.316V	3.153V	4.92%	Pass
5VSB	5.066V	5.007V	1.16%	Pass

Advanced Transient Response at 20% – 20ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.099V	11.941V	1.31%	Pass
5V	4.995V	4.849V	2.92%	Pass
3.3V	3.316V	3.119V	5.94%	Fail
5VSB	5.066V	5.025V	0.81%	Pass

Advanced Transient Response at 20% – 1ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.098V	11.972V	1.04%	Pass
5V	4.996V	4.852V	2.88%	Pass
3.3V	3.316V	3.119V	5.94%	Fail
5VSB	5.067V	5.018V	0.97%	Pass

Advanced Transient Response at 50% – 200ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.095V	11.998V	0.80%	Pass
5V	4.991V	4.866V	2.50%	Pass
3.3V	3.311V	3.141V	5.13%	Pass
5VSB	5.029V	4.970V	1.17%	Pass

Advanced Transient Response at 50% – 20ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.095V	11.935V	1.32%	Pass
5V	4.991V	4.839V	3.05%	Pass
3.3V	3.311V	3.106V	6.19%	Fail
5VSB	5.030V	4.982V	0.95%	Pass

Advanced Transient Response at 50% – 1ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.092V	11.943V	1.23%	Pass
5V	4.992V	4.841V	3.02%	Pass
3.3V	3.312V	3.108V	6.16%	Fail
5VSB	5.030V	4.985V	0.89%	Pass

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(Image credit: Tom's Hardware)

Results 25-29: Transient Response

The transient response at +12V, which is the most crucial rail, is good. The voltage deviations are high on the minor rails, though, especially at 3.3V.

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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(Image credit: Tom's Hardware)

Turn-On Transient Response Scope Shots

The voltage at +12V takes some time to reach the nominal value. This won't create any problems, though.

Power Supply Timing Tests

There are several signals generated by the power supply, which need to be within specified, by the ATX spec, ranges. If they are not, there can be compatibility issues with other system parts, especially mainboards. From year 2020, the PSU's Power-on time (T1) has to be lower than 150ms and the PWR_OK delay (T3) from 100 to 150ms.

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T1 (Power-on time) & T3 (PWR_OK delay)	Row 0 - Cell 1	Row 0 - Cell 2
Load	T1	T3
20%	78	316
100%	88	316

The PWR_OK delay is out of the 100-150ms region, so according to the ATX spec, the PSU does not meet the requirements of the alternative sleep mode.

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-degree Celsius increase can cut into a cap's useful life by 50%. 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	12.0 mV	10.3 mV	6.8 mV	5.5 mV	Pass
20% Load	16.9 mV	12.9 mV	8.6 mV	5.7 mV	Pass
30% Load	20.0 mV	12.9 mV	9.6 mV	5.9 mV	Pass
40% Load	22.5 mV	12.9 mV	10.1 mV	5.9 mV	Pass
50% Load	24.4 mV	14.2 mV	10.5 mV	6.3 mV	Pass
60% Load	25.9 mV	15.2 mV	11.0 mV	7.2 mV	Pass
70% Load	27.6 mV	16.8 mV	11.0 mV	6.7 mV	Pass
80% Load	28.7 mV	17.7 mV	13.7 mV	8.5 mV	Pass
90% Load	29.6 mV	21.1 mV	14.3 mV	9.1 mV	Pass
100% Load	31.1 mV	24.3 mV	15.5 mV	8.4 mV	Pass
110% Load	33.3 mV	24.8 mV	16.4 mV	9.5 mV	Pass
Crossload 1	16.0 mV	17.7 mV	11.8 mV	5.4 mV	Pass
Crossload 2	30.6 mV	16.3 mV	13.9 mV	7.6 mV	Pass

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(Image credit: Tom's Hardware)

Results 30-33: Ripple Suppression

The lack of in-cable capacitors doesn't allow for flawless ripple suppression. Nonetheless, the PSU achieves satisfactory performance in this section.

Ripple At Full Load

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(Image credit: Tom's Hardware)

Ripple Full Load Scope Shots

Ripple At 110% Load

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(Image credit: Tom's Hardware)

Ripple 110% Load Scope Shots

Ripple At Cross-Load 1

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(Image credit: Tom's Hardware)

Ripple CL1 Load Scope Shots

Ripple At Cross-Load 2

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(Image credit: Tom's Hardware)

Ripple CL2 Load Scope Shots

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. For example, it can be the cause of increased static noise in your headphones or/and speakers.