A power supply is an electrical device that supplies power to an electrical load. The power supply draws current from an input power source like main power lines, 电池, 燃料电池, 和发电机, and delivers the correct 电压, current 和频率 to the load.
Power supplies can be standalone, or built into the load they power. Standalone supplies like benchtop units, inverters and converters typically limit main line current to safe levels before delivering power to the load. Built-in units perform similar functions for desktop computers and other consumer electronics devices.
Power supply units can deliver AC or DC power, convert from one signal to the other, 调节电流, 电压, 和频率, provide overload protection, and provide an uninterruptible source of power in the event of lost source power.