Commercial AC power distributed from power plants cannot be supplied directly to the ICs and other electronic components built into electronic devices in automated office and factory equipment without destroying the components due to the high voltage of commercial AC power. Devices called power supplies or regulated DC power supplies are therefore required to convert commercial AC power into regulated DC power to drive ICs and other electronic components.

The methods for controlling Regulated DC Power Supplies can be largely classified into the following two types. Switch-mode Power Supplies and linear Power Supplies are generally referred to as Power Supplies. Currently, switch-mode Power Supplies are the most prevalent.

Switch-mode power supplies convert commercial AC power into the required high-frequency DC power using the high-speed switching of semiconductors. Switch-mode power supplies are so compact, light, and efficient that they are used as power supplies by most electronic devices.