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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% – 20ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.150V	11.979V	1.40%	Pass
5V	5.001V	4.917V	1.67%	Pass
3.3V	3.299V	3.183V	3.53%	Pass
5VSB	5.078V	5.041V	0.73%	Pass

Advanced Transient Response at 20% – 10ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.148V	11.989V	1.31%	Pass
5V	5.002V	4.915V	1.73%	Pass
3.3V	3.298V	3.182V	3.51%	Pass
5VSB	5.078V	5.029V	0.97%	Pass

Advanced Transient Response at 20% – 1ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.146V	12.006V	1.15%	Pass
5V	5.002V	4.905V	1.95%	Pass
3.3V	3.298V	3.184V	3.44%	Pass
5VSB	5.078V	5.033V	0.88%	Pass

Advanced Transient Response at 50% – 20ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.121V	12.027V	0.77%	Pass
5V	4.995V	4.907V	1.76%	Pass
3.3V	3.291V	3.169V	3.71%	Pass
5VSB	5.044V	5.002V	0.84%	Pass

Advanced Transient Response at 50% – 10ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.120V	12.031V	0.73%	Pass
5V	4.995V	4.904V	1.81%	Pass
3.3V	3.291V	3.169V	3.70%	Pass
5VSB	5.044V	4.993V	1.01%	Pass

Advanced Transient Response at 50% – 1ms

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Voltage	Before	After	Change	Pass/Fail
12V	12.122V	12.040V	0.68%	Pass
5V	4.995V	4.908V	1.74%	Pass
3.3V	3.291V	3.172V	3.61%	Pass
5VSB	5.044V	4.999V	0.90%	Pass

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EVGA 1000 P6 — (Image credit: Tom's Hardware)

Transient response is good on all rails but 3.3V, where despite the low deviation, voltage drops below 3.2V the moment the transient load is applied on this rail. With a higher nominal voltage at 3.3V, this wouldn't be an issue.

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 only found a small step at 5VSB, which is nothing to worry about. Both 12V slopes are fine.

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. Since 2020, the PSU's Power-on time (T1) has had to be lower than 150ms and the PWR_OK delay (T3) from 100 to 150ms, to be compatible with Alternative Sleep Mode.

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PSU Timings Table
T1 (Power-on time) & T3 (PWR_OK delay)
Load	T1	T3
20%	90.5ms	132ms
100%	92ms	128.5ms

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PSU Timing Charts

The PWR_OK delay is within the 100-150ms region, so the PSU supports the alternative sleep mode recommended by the ATX spec.

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	5.5 mV	4.6 mV	5.3 mV	8.6 mV	Pass
20% Load	8.5 mV	4.4 mV	5.4 mV	9.4 mV	Pass
30% Load	8.1 mV	5.5 mV	5.9 mV	10.1 mV	Pass
40% Load	7.2 mV	6.1 mV	6.6 mV	10.8 mV	Pass
50% Load	7.6 mV	7.9 mV	7.7 mV	13.8 mV	Pass
60% Load	7.6 mV	8.2 mV	7.6 mV	10.9 mV	Pass
70% Load	7.8 mV	8.8 mV	8.0 mV	16.9 mV	Pass
80% Load	8.4 mV	8.4 mV	9.8 mV	16.9 mV	Pass
90% Load	8.6 mV	11.4 mV	13.4 mV	14.4 mV	Pass
100% Load	12.4 mV	14.1 mV	14.9 mV	15.1 mV	Pass
110% Load	12.4 mV	16.2 mV	16.4 mV	15.3 mV	Pass
Crossload 1	6.0 mV	6.4 mV	10.3 mV	9.7 mV	Pass
Crossload 2	5.4 mV	7.3 mV	5.7 mV	8.2 mV	Pass
Crossload 3	5.8 mV	4.1 mV	10.0 mV	8.3 mV	Pass
Crossload 4	12.4 mV	12.4 mV	13.4 mV	13.9 mV	Pass

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Ripple suppression is excellent on all rails.

Ripple At Full Load

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Ripple At 110% Load

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Ripple At Cross-Load 1

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Ripple At Cross-Load 4

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EMC Pre-Compliance Testing – Average & Quasi-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 nearby devices.

Electromagnetic Interference (EMI) stands for the electromagnetic energy a device emits, and it can cause problems in other nearby devices if too high. For example, it can be the cause of increased static noise in your headphones or/and speakers.