The Secret to Buying a Good Power Supply

November 4, 2015 | By Joey Cheng | PCDIY

Nowadays, there are more and more enthusiasts that care about the performance and overall quality of their PSU before buying it. Users may check PSU review sites like JonnyGURU or HardOCP to make sure the PSU they’re getting is high quality. Typically, people will trend towards a reputable company due to word of mouth and the conceived idea of quality based on brand. More and more media sites are investing in equipment and professional reviewers to specifically test PSUs. While these reviews are important and give keen insight, many people don’t understand them.

Some readers still don’t know what those parameters mean, but the reviews are easier to understand based on the end score using the ten point scale. So in this article, I would like to go over those specific parameters mean and why they’re important.

Ripple Noise

Ripple Noise is the variation in voltage that SMPSs (Switching Mode Power Supplies) give off because the SMPS is oscillating while powered on. The output capacitor is charging and discharging continuously to create an AC based on nominal output voltage. Ripple noise is measured in mV (milli-volts). Ripple noise is variable and changes according to load. In Switching Mode Power Supplies, ripple noise is impossible to completely remove, so 1% of nominal output voltage has been set as the standard for ripple noise. Computer PSUs use +3.3V, +5V, +12V, -12V, and +5Vsb outputs, with Intel defining the standard of ripple amount as seen below.

Ripple noise is combined with nominal output which means the output voltage can end up being too high or low by this inference due to the variation in ripple noise. Voltage being too high or low may cause your components to have errors. Abnormally high or low voltage can cause system shutdown and in extreme cases may burn out components, especially to HDDs. Here at NZXT, we prioritize the elimination of ripple noise so we test our product not only at ambient temperature condition, but also at rated operation temperature condition.

Voltage Regulation

Voltage Regulation refers to the PSU maintaining accurate output voltage. Does  voltage regulation truly matter for PC components? Not as much as you think, but people rightfully want the best of the best for their PCs. That’s why most editors test this specification and define that a good PSU shall be within ±2%, although Intel stands for ±5% for major rails and ±10% for -12Vdc. In fact, PC components allow a variable input voltage range which is 10% tolerance from nominal output of PSU in design. For example, motherboards can allow input voltage from 10.8V up to 13.2V for +12Vdc rail.  But of course, a good PSU shall provide the most accurate output. Intel’s standard of voltage ripple is seen in the table below.

Hold-up Time

Hold-up Time refers to the time the PSU can maintain output power when the AC input is interrupted through either the main cutting off, brown out, or sag. There is little we can do when the AC mains break off when playing games or processing something because the input is completely gone – but we do care about maintaining continuity and power when the AC main suffers sag or brown out. Hold-up Time effects the cost of a power supply a fair amount. Standard Hold-up Time is approximately 16ms which is the cycle time of 60Hz AC mains. Some PSU providers utilize a 12ms hold-up time to cut costs. Review sites like JonnyGURU will usually test hold-up time claims, differentiating between the lower and higher quality PSUs. The bulk capacitor is the key component in the PSU that increases hold-up time and also impacts overall stability of switching power.

Cross Regulation

Cross Regulation is a stability and consistency of PSU output when load is unbalanced. Most of professional media sites test this value using a crossload test. They are loading all of the rails and measuring the accuracy in load, efficiency and voltage between the different rails. PSUs utilize a main regulator to control and power each rail, good cross regulation will allow your PC to run uninterrupted or affected by load changes. Extremely poor cross regulation will cause lousy voltage regulation and make many bad quality power supplies crumple to ground in a heap when voltage changes. Less serious cross load problems will cause system crashes.


Most PSU providers will highlight their PSUs are fully protected such as OVP (Over Voltage Protection), OCP (Over Current Protection), OPP (Over Power Protection), OTP (Over Temperature Protection), UVP (Under Voltage Protection), and SCP (Short Circuit Protection). These are fairly self explanatory, with these protection sets designed to keep your PSU up and running in the event of an error. NZXT tests for these parameters by using ATE (Auto Test Equipment) in factory.

PCB Layouts

The last part of this article is about the PCB layout and components placement to a PSU. A good PSU layout can ensure overall performance and a long product life. A clean layout with good components placement also impresses enthusiasts. We are not saying our product is the best design for PCB layout, but we do care about airflow and ensuring product longevity. We use copper bars to deliver energy from main board to modular board, saving space and ensuring good heat dissipation. We place those heatsinks, mylar-sheet, and an acrylic fan gate to create air tunnels to dissipate heat for those hotspots such as transformers, coils, capacitors, and semiconductors.

Got Any Questions?

We took your feedback into consideration with this blog post and really tried to delve into the more dense PSU stuff without making it too technical or hard to read. The power supply is not an easy component to get a full grasp on so we will continue to share more about PSU knowledge giving different point of views to help enthusiasts and novice builders alike take these specs into account. As always, feel free to contact us if you have any questions!


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Joey Cheng

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