The power supply unit is the most vital component in the operation of a personal computer (PC). This unit supplies power to the other components in a computer – it converts alternating current (AC) from an electrical outlet to direct current (DC) which is needed by the computer. Power supplies use ‘switcher technology’ to convert AC input into lower DC voltages. Each component requires different voltage and current to function. The power supply is able to switch the voltages and distribute it to all components. The typical voltages required inside a computer are 3.3 volts (V), 5V and 12V. The two lower voltages are generally used for digital circuitry, whereas 12V is used to run the motors in disk drives and cooling fans.

Power supplies are sold based on their total power output, also known as the wattage. When you are selecting a power supply, you need to find one that will provide enough power for all the components connected to the system and has sufficient connections for all these components. It is important that the power supply can support the various voltage levels and the current supplied. The more advanced you want your computer to become, the more robust your power supply has to be.

Most power supplies should have a lifespan of 100, 000 hours or more. This is referred to as the mean time before failure (MTBF). Ensure you find out what the MTBF is for your power supply before you select one. Another feature to check is whether the power supply is equipped with a short circuit protection feature. This will prevent the computer components from drawing excess currents, leading to the destruction of internal chips.

You will also want to purchase a power supply that does not make a loud noise. The main reason for a power supply to be noisy is an indicator that heat is not being dissipated fast enough. This means that the fan has to work extra hard to keep temperatures low. Make sure that you buy a power supply with a powerful fan to effectively dissipate the heat away. Also, most of the power supplies in the market are of the ATX form factor. If you are using a micro ATX computer case however, you will have to get a micro ATX power supply for it to be able to fit inside your case.