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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