PSU

By Tyler Downer
3/15/08

What is a PSU?

A PSU, or Power Supply Unit, is the unsung hero of the computer. Just as an army marches on it's stomach, so a computer runs on it's power supply. That is a PSU's job, to give all of the computer components just the right amount of power in the right voltage and amperage.

Household power cannot be piped directly into a computer as is. It must be cleaned, converted and divided to the correct connector. This is a complex job that can only be done by the PSU.

How it Works

The typical house in the US has 120-volt AC (Alternating Current) electricity. However, most computer components need 12-volt DC (Direct Current). This is where a PSU comes in. A transformer in the PSU takes the 120-volt AC, and converts it to 12-volt AC. But wait, computers need Direct Current, not Alternating Current. So next a rectifier changes the AC to DC. Finally, a capacitor evens the power out, preventing minor surges, spikes and other noise that could damage the delicate components. Finally it uses different connectors to feed to cleaned, ready electricity to various components. This processes produces a lot of heat. Computers can only take so much heat, the cooler the better. To combat this, almost every PSU includes a heatsink and fans that blow the hot air out of the computer and suck more in.

What a PSU does not do

While a PSU does clean out some line noise, and some high-end models do a very good job, a very high surge can still wipe it and your computer out. To prevent that, you should always invest in a good surge protector to absorb most of the impact. These are getting more and more inexpensive and a high-quality one with battery backup can often be purchased for around $100. Please note that after a high surge, the surge protector will usually be wiped out and need to be replaced. Also, a PSU cannot provide unlimited power. Each model is designed for a certain range of watts, for example, <350 watts. However, this is only a concern if you have added more hardware to your computer or built it your self.

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