Power Supplies

power supply As computer requires a direct current (DC) to operate and a computer power supply converts the alternating current (AC) to direct current.

Power Supply Specifications

The important specifications when considering power supplies include AC input, DC output, power supply style, form factor, common features, and environmental parameters.

Style

Computer motherboards are available in various styles and cases. Usually a power supply style is according to the case style. The power supply styles commonly available include AT, ATX, Flex ATX, micro ATX, NLX, LPX, TFX, and SFX power supplies.

AC and DC characteristics

  • AC input is concerned with AC input voltage and frequency. Input voltage can be 115 VAC and 230 VAC with frequencies 50 Hz, 60 Hz, or 400 Hz.
  • DC output considerations focus on DC output current corresponding to the DC output voltage, number of outputs, and output power of the supply. Common choices available for power supplies provide output voltage as + / - 3.3 V, + / - 5 V, + / - 12 V, + / - 15 V, + / - 24 V, and + / - 48 V.

Features

Some extra feature common in most power supplies can be integral heat sink, over voltage and over current protection, short circuit protection, power factor correction, remote on /off switches, water cooled, and fan cooled. Some power supplies contain heat sinks for cooling whereas in some cooling fans are used. Moreover some power supplies are water-cooled. Some power supplies contain internal over voltage and over current protection circuitries. When voltage or current increases from the maximum supplied voltage of the power supply the circuitry brings the voltage or current back to original level.
Phase difference between current and voltage is a big concern in electronic circuits. Power supplies with power factor correction correct this phase difference and optimize the output. Some power supplies contain remote on / off switch that allows the computer to control power supply remotely. Moreover some power supplies contain internal circuitry that automatically recovers or protects the system in case of any short circuit.

Power Supply Types

Powers supplies are available in number of styles supporting technologies as mentioned earlier such as AT, ATX, or PC 104. Common choices for power supplies can be categorized as: