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How computer power supplies work – KitGuru Guide

KitGuru takes the subject of power supplies very seriously, this is why we have a dedicated team behind the scenes, experts in their specific fields to produce some of the most detailed power related reviews online. Today one of our resident experts ‘IronLaw’ will explain exactly how a computer power supply works. While this can be a complex subject matter, if you take your time reading it you will find it is not a ‘dark art’ subject, or something impossible to understand. We hope this will be both educational and informative.

Power supply units are perhaps the most neglected piece of equipment in the history of technology. It is no overstatement to say that they are the most critical part of almost every electronic device as they are the one component which is absolutely vital to their operation. Almost no technology equipment can operate without them. That is because no equipment can actually operate by directly using the utility grid AC voltage, which also varies in level and frequency depending on your position on the planet. It is the power supply’s job to convert that AC voltage to another form, suitable for the equipment. Or, to be even more accurate, the definition of a power supply is that “it is an apparatus designed to convert one form of electric energy to another“.

Several people may believe the power supplies are limited to computer applications. That is incorrect since almost every piece of technology needs a power supply to operate. Some examples include your phone charger, your TV, your alarm clock and any other electronic household equipment. Users are simply not aware of the presence of power supplies because they are often integrated into the equipment. They are not replaceable because those devices have no expandability or upgradeability and are (hopefully!) designed to exceed the product’s lifetime. For example, you cannot replace the power supply of your TV because there is no way to upgrade or expand your TV and force it to require more power, meaning that ultimately there is no reason to perform a power supply upgrade. Computers are an entirely different matter; they are fully expandable and customizable, meaning that not only each and every one of them has different power needs but that the needs of every single computer can be altered several times during its operational lifetime.

A power supply transforming the utility grid AC voltage to DC voltage for the equipment to use must perform certain functions at the highest possible efficiency and at the lowest possible cost. The basic functions usually are:

  • Rectification – Convert the input AC voltage to DC voltage.
  • Voltage transformation – Adjust the supplied voltage to the required levels.
  • Filtering – Smoothen the ripple of the supplied voltage.
  • Regulation – Control the supplied voltage regardless of line, load and/or temperatures changes.
  • Isolation – Electrically isolate the input voltage source from the output.
  • Protection – Prevent any damaging power phenomena from reaching or take effect at the output.

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  • Tim

    Bloody Nora IronLaw, that certainly is detailed. I made it to page 2, now I need a glass of coke (cola not powder). I shall return later once I absorb the basics !

  • Tech Head

    I am one of the most demanding readers on the face of the planet. The standard of editorial content on this site is without a doubt leading the way on the net right now. Some of the news stories are very ermm interesting, but the reviews are fantastic.

  • Flo

    I have bookmarked this, I shall spend a few hours Sunday afternoon chilling and trying to work this out. I need to read this at a snails pace to get to grips with it all.

  • Eric K

    Well this is taking power supplies to the next level. I got lost in parts, and im quite technical, but its well written and rather complex. Nice idea these articles, at least you guys expect the readers to know more than the usual tech site reader

  • Stefan

    Thank you, thank you , thank you.; I always wanted something like this, with images and easy to understand text. I have struggled on page 4 and 5, but I have picked up more from this than any other PSU related article on the net.

  • fluffychicken

    A hell of a lot of work in this Ironlaw. Thank you very much for making all this effort to educate us peasant mortals πŸ™‚


    brain overload………… ekkk.

    I am just too stupid to understand half of this, but thanks anyway ! the last page was as far as I made in understanding it all :p

  • dilbert

    Stunning work IronLaw, technically way above my level, but I feel a little better for having read it. I love the PSU reviews on KitGuru too. at the same level as Hardocps (which are also excellent).

  • derek

    With standard of content like this on a regular basis, you will go far ! top marks KG

  • Flo

    Christ on a stick. lost for words. This is more for apprentice engineers !

  • Jeo

    Normally I see these guides and think, oh here we go again, some idiot reviewer ranting on about something stupid and trying to understand it himself.

    Not in this case. Ironlaw is a cut above! really really enjoyed this one.

  • Trev Mang

    **claps** – I understood most of it, which is surprising as I only know the basics about power supplies. I hope to see more of these. I would like one explaining what exactly we need to buy when looking for a PSU, single rail 12v? multiple rails. and making sense of actual ratings. who needs 1200W psus for instance? do we ?!

  • Brad

    Well that was surprising. very very good reading. bit complex for me in parts, but I picked up bits and pieces.

  • Cecil

    Ironlaw, thank you. very informative reading for a friday morning πŸ™‚ now off to work to type in numbers.

  • Luke Trent

    lol, I just read something so badly written on bittech, then I come here to read this. its like comparing nickelodean to the discovery channel.

  • Frank Smith

    I feel educated, thank you πŸ™‚

  • Dark Knight

    For such a complex article it is very informative, a little complex for this geek, but im sure many people love all this about PSU’s. The last page was helpful :p

  • Gareth Cringle

    I shall email Zardon for permission to use parts of this for an edu guide I am writing for college kids.

  • Fraline

    Brilliant piece of work. 10/10

  • Davey

    I find power supplies totally confusing. I just buy one and get a good one after reading several reviews online. I actually ordered the thermaltake one after reading the review on kitguru. This was educational but honestly a little over my head for 70 percent of it. I learned a little, which is more than I normally do every day !

  • dbdb

    Fantastic writing and very educational as other people have said. I read the power supplies reviews here in the last month and I prefer them to johnny guru. Johnny is great with PSUs but his writing style annoys me, jokes are fine, but half the review is him trying to be funny. The reviews on this site are just as detailed but more focused. I hope you get the corsair 1200w PSU to review, I want to order it, but its 260 here and im not sure if its worth it.

  • tech head

    read it in detail – very good work indeed Ironlaw, you know your work πŸ˜‰

  • My brain hurts.

    Where do i find the for dummies version?
    Nice work mate πŸ˜‰

  • Cool and easy to understand

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