3.14.1 The Power Supply

Learn the basic functions of a power supply, the hardware component that provides electricity to the system.

An ATX power supply means that the battery adheres to the ATX form factor specifications.

Back Panel

On the back panel, you'll find a power switch and sometimes a voltage selector switch, used to toggle between 115-230 volts to output, depending on how much power your system needs. Other types of power supplies automatically switch between voltages, which is why they specify if and what voltage range they're compatible with, typically 100-240 volt. Most power supplies also have air holes on the back, and some even have their fan there instead on the top panel.

AC to DC Power

On the back panel of all power supplies is a C14 connector. This is where the power cord from the wall plugs into. However, the electricity from the wall is 120 volt AC power, while the components inside a computer use DC power. The battery supply is responsible for converting the AC power from the wall to DC power for use.

The 120 volt AC power goes to the power supply where it's converted into three voltage levels: 12, 5, and 3.3 volts, all for use with different components that have different voltage requirements.

Technical Stuff

Each voltage output circuit is referred to as a rail and can power multiple devices. They're known as dual rail power supplies. Separate rails balance the power load between multiple circuits, preventing any one circuit from becoming overloaded.

Also, different nations/regions have different power outlet standards or whatever. You can change the voltage using the manual voltage switch on the power supply. If there isn't one, that means it most likely automatically does the voltage conversion and no action is necessary for mismatched power voltages.

Wire Bundles & Connectors

Every power supply has a wire bundle, which contains a variety of connectors that plug into components and provide them with their required voltage of DC power. The different colored wires play different roles and have different voltages.

• Black - Ground
• Yellow - +12V
• Orange - +3.3V
• Red - +5V

Now, just because a power supply has 10 hard drive connectors doesn't mean it can power 10 hard drives.

For that, you'll need to know wattage. All power supply use wattage as their standard power rating, which specifies the maximum power output it can handle. For most desktop computers a 350 watt power supply should be sufficient. However, when you start to add other components that also need power, such as the optical and hard drives along with GPUs, it's better in the long run to invest in a more powerful power supply like a 500 or 650 watt one.

Thermal Management

Oh yeah the fan on a power supply also functions as a case fan, so it's placed strategically to help with the case's airflow and stuff.

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