main article
technology > instrumentation > power supply & control
Download download article

Power supply

Article index
 General description
 Electrical power supplies
 Computer power supply
A power supply (sometimes known as a power supply unit or PSU) is a device or system that supplies electrical or other types of energy to an output load or group of loads. The term is most commonly applied to electrical energy supplies.

General description

The complete range of power supplies is very broad, and could be considered to include all forms of energy conversion from one form into another. Conventionally though, the term is usually confined to electrical or mechanical energy supplies. Constraints that commonly affect power supplies are the amount of power they can supply, how long they can supply it for without needing some kind of refueling or recharging, how stable their output voltage or current is under varying load conditions, and whether they provide continuous power or pulses.

The voltage regulation of power supplies is done by incorporating circuitry to tightly control the output voltage and/or current of the power supply to a specific value. The specific value is closely maintained despite variations in the load presented to the power supply's output, or any reasonable voltage variation at the power supply's input.

Electrical power supplies

This term covers the mains power distribution system together with any other primary or secondary sources of energy such as:
  • Conversion of one form of electrical power to another desired form and voltage. This typically involves converting 120 or 240 volt AC supplied by a utility company (see electricity generation) to a well-regulated lower voltage DC for electronic devices. For examples, see switched-mode power supply, linear regulator, rectifier and inverter (electrical).
  • Batteries
  • Chemical fuel cells and other forms of energy storage systems
  • Solar power
  • Generators or alternators (particularly useful in vehicles of all shapes and sizes, where the engine has rotational power to spare, or in semi-portable units containing an internal combustion engine and a generator) (For large-scale power supplies, see electricity generation.) Low voltage, low power DC power supply units are commonly integrated with the devices they supply, such as computers and household electronics.

Computer power supply

A computer power supply typically is designed to convert 120 V or 240 V AC power from the electrical company to usable power for the internal components of the computer. The most common computer power supply is built to conform with the ATX form factor. This enables different power supplies to be interchangeable with different components inside the computer. ATX power supplies also are designed to turn on and off using a signal from the motherboard (PS-ON wire), and provide support for modern functions such as the Standby mode of many computers.

Computer power supplies are rated for certain wattages based on their maximum output power. Typical wattages range from 200 W to 500 W, although some new personal computers with high energy requirements may draw as much as 1000 W (1 kW).

Most computer power supplies have a large bundle of wires emerging from one end. One connector attached to the opposite end of some wires goes to the motherboard to provide power. The PS-ON wire is located in this connector. The connector for the motherboard is typically the largest of all the connectors. There are also other, smaller connectors, most of which have four wires: two black, one red, and one yellow. Unlike the standard electrical wire color-coding, each black wire is a Ground, the red wire is +5 V, and the yellow wire is +12 V.

Inside the computer power supply is a complex arrangement of electrical components, ranging from diodes to capacitors to transformers. Also, many power supplies have metal heatsinks and fans to dissipate large amounts of heat produced. It is dangerous to open a power supply while it is connected to an electrical outlet as high voltages may be present even while the unit is switched off.

In desktop computers, the power supply is a small (PSU) box inside the computer; it is an important part of the computer because it provides electrical power in a form that is suitable for every other component inside or attached to the computer in order for it to work. If only a small voltage is needed, the mains power needs to be transformed to a suitable level in order for the component to work.

In portable computers there is usually an external power supply that produces low voltage DC power from a mains electrical supply (typically a standard AC wall outlet). Circuitry inside the portable computer uses this transformed power to charge the battery as needed, in addition to providing the various voltages required by the other components of the portable computer.
forumReply to this article
All fields are required. Your personal information will not be displayed on our website. Hyfoma does not supply machines, but only refers to the companies that do. Most of the suppliers listed supply machines for the food industry, and do not produce food themselves.

Name: Email:
Function: Company:

power supply & control

A power supply (sometimes known as a power supply unit or PSU) is a device or system that supplies electrical or other types of energy to an output load or group of loads. The term is most commonly applied to electrical energy supplies.... read full description
Endress+Hauser is a global supplier of process automation...