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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	12.033V	11.935V	0.81%	Pass
5V	5.047V	4.990V	1.13%	Pass
3.3V	3.307V	3.201V	3.21%	Pass
5VSB	5.032V	4.993V	0.78%	Pass

Advanced Transient Response at 20% – 20ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.032V	11.902V	1.08%	Pass
5V	5.047V	4.980V	1.33%	Pass
3.3V	3.307V	3.187V	3.63%	Pass
5VSB	5.032V	4.983V	0.97%	Pass

Advanced Transient Response at 20% – 1ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.078V	11.962V	0.96%	Pass
5V	4.931V	4.790V	2.86%	Pass
3.3V	3.309V	3.100V	6.32%	Fail
5VSB	4.906V	4.806V	2.04%	Pass

Advanced Transient Response at 50% – 200ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.027V	11.935V	0.76%	Pass
5V	5.036V	4.977V	1.17%	Pass
3.3V	3.300V	3.187V	3.42%	Pass
5VSB	5.015V	4.973V	0.84%	Pass

Advanced Transient Response at 50% – 20ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.022V	11.905V	0.97%	Pass
5V	5.037V	4.968V	1.37%	Pass
3.3V	3.301V	3.172V	3.91%	Pass
5VSB	5.015V	4.959V	1.12%	Pass

Advanced Transient Response at 50% – 1ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.023V	11.911V	0.93%	Pass
5V	5.037V	4.971V	1.31%	Pass
3.3V	3.301V	3.170V	3.97%	Pass
5VSB	5.015V	4.972V	0.86%	Pass

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(Image credit: Tom's Hardware)

Results 25-29: Transient Response

The transient response at +12V is tight, and this is what matters the most in contemporary systems. We are also fully satisfied by the performance of the 5V and 5VSB rails, while the 3.3V rail might not have high deviations. Still, its voltage drops below 3.2V and in one test it fails to keep it above 3.14V.

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

Almost flawless performance here. We only notice a minor spike at 5VSB.

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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PSU Timings Table
T1 (Power-on time) & T3 (PWR_OK delay)
Load	T1	T3
20%	84ms	282ms
50%	88ms	284ms

The PWR_OK delay is out of the 100-150ms region, so the PSU does not support the alternative sleep mode, which will be a requirement by the ATX v2.52 from 2020.

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	9.7 mV	6.8 mV	25.8 mV	9.3 mV	Pass
20% Load	9.7 mV	4.9 mV	13.1 mV	8.7 mV	Pass
30% Load	9.4 mV	4.1 mV	12.1 mV	8.5 mV	Pass
40% Load	11.1 mV	5.0 mV	12.1 mV	8.9 mV	Pass
50% Load	14.7 mV	5.6 mV	14.0 mV	9.5 mV	Pass
60% Load	16.6 mV	5.8 mV	14.8 mV	9.9 mV	Pass
70% Load	15.8 mV	5.8 mV	15.3 mV	8.8 mV	Pass
80% Load	17.7 mV	6.4 mV	16.6 mV	9.4 mV	Pass
90% Load	18.4 mV	7.0 mV	16.6 mV	9.3 mV	Pass
100% Load	25.4 mV	7.5 mV	18.8 mV	11.0 mV	Pass
110% Load	26.5 mV	7.3 mV	20.1 mV	11.2 mV	Pass
Crossload 1	11.4 mV	5.4 mV	18.6 mV	9.7 mV	Pass
Crossload 2	24.7 mV	6.8 mV	15.6 mV	10.8 mV	Pass

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(Image credit: Tom's Hardware)

Results 30-33: Ripple Suppression

The ripple suppression is good on all rails.

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.