A system that converts AC current from the wall outlet into the DC currents required by electronic circuits. A computer power supply converts AC into multiple DC voltages. For example, 12 volts is commonly used for drives, while 3.3v and 5v are used by the chips and other motherboard components.
Switching Power Supplies
Power supplies known as "switching" power supplies are commonly used. Their name is derived from the type of circuit used to change the voltage. For more details, see transformer. See power adapter.
This monitor displays the typical three voltages generated by a PC power supply.
One Size Does Not Fit All
Like everything else in our high-tech world, power supplies come in myriad sizes and shapes; witness this table full of different units from Sparkle Power Inc. (www.sparklepower.com).
Laptops use an external power supply, called a "power adapter" or "power brick." It converts AC to a single DC voltage that goes to the laptop's internal power supply, which generates all other required voltages. External adapters are used to reduce the size and weight of the laptop, yet they typically ride along in the laptop case, adding back the weight after all.