Abbreviated as PS or P/S, a power supply or PSU (Power Supply Unit) is a hardware component of a computer that supplies all other components with power. The power supply converts a 110-115 or 220-230 volt AC (Alternating Current) into a steady low-voltage DC (direct current) usable by the computer and rated by the number of watts it generates. The picture shows an Antec True 330, a 330 Watt power supply.
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Caution
Never open the casing of a power supply. It contains capacitors capable of holding a strong electrical charge, even if the computer is off and unplugged for an extended period.
Tip
You can protect your power supply and your computer from surges and voltage drops by investing in a UPS (Uninterruptible Power Supply). If you cannot afford a UPS, make sure the computer is at least plugged into a surge protector.
The power supply is located at the back of the computer, usually at the top. However, many more recent tower computer cases house the power supply at the bottom back of the case. In a desktop computer case (all-in-one), the power supply is located at the back left or back right.
Below are parts you may find on the back of the power supply.
On the front of the power supply, which is not visible unless the computer is opened, you find several cables. These cables connect to the computer motherboard and other internal components. With an ATX (Advanced Technology eXtended) motherboard, a power supply connects to the motherboard using an ATX style connector and may have one or more of the following power cables.
Below are parts inside a power supply.
The order that these internal power supply components function is as follows.
Everything contained in the computer chassis is powered by the power supply. For example, the motherboard, RAM (Random-Access Memory), CPU (Central Processing Unit), hard drive, disc drives, and most video cards (if the computer has one) are all drawing power from the power supply. Any other external devices and peripherals, such as the computer monitor and printer, have a power source or draw power over the data cable like some USB (Universal Serial Bus) devices.
Note
If the computer is a laptop or an All-in-One computer, the display is powered by the computer power supply.
While the computer is on, the fan(s) inside a power supply should always be running. If the fan is not running (spinning), either the computer is not working or the fan has failed and the power supply should be replaced.
Note
Some power supplies have variable controls that may increase or decrease the speed of the fan depending on its temperature. However, it should always be spinning.
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If there is any one component that is absolutely vital to the operation of a computer, it is the power supply. Without it, a computer is just an inert box full of plastic and metal. The power supply unit, also known as a PSU, converts the alternating current (AC) line from your home to the direct current (DC) needed by the personal computer. In this article, we'll learn how PC power supplies work and what the wattage ratings mean.
In a personal computer (PC), the power supply is the metal box usually found in a corner of the case. The power supply is visible from the back of many systems because it contains the power-cord receptacle and the cooling fan. A typical PSU will have integrated connectors to send power to the motherboard, microprocessors, and SATA storage. Laptops and mini-PCs usually have their power supplies separate from the computer assembly, instead of integrated into their charging cables.
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Power supplies, often referred to as "switching power supplies", use switcher technology to convert the AC input to lower DC voltages. The typical voltages supplied are:
3.3 volts
5 volts
12 volts
The 3.3 and 5 volts are typically used by digital circuits, while the 12 volt is used to run motors in disk drives and fans. The main specification of a power supply is in watts. A watt is the product of the voltage in volts and the current in amperes or amps. If you have been around PCs for many years, you probably remember that the original PCs had large red toggle switches that had a good bit of heft to them. When you turned the PC on or off, you knew you were doing it. These switches actually controlled the flow of 120-volt power to the power supply.
Today you turn on the power with a little push button, and you turn off the machine with a menu option. The operating system can send a signal to the power supply to tell it to turn off. The push button sends a 5-volt signal to the power supply to tell it when to turn on. The power supply also has a circuit that supplies 5 volts, called VSB for "standby voltage" even when it is officially "off", so that the button will work.
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