Pulse-width modulation

Pulse-width modulation, also known as pulse-duration modulation or pulse-length modulation, is a method of representing a signal as a rectangular wave with a varying duty cycle. It controls the average power or amplitude delivered by an electrical signal by switching the supply fully on and off faster than the load can respond, so that the longer the switch stays on, the more power reaches the load. Its main advantage is very low power loss in the switching devices, since there is almost no current when the switch is off and almost no voltage drop when it is on. It suits inertial loads such as motors, works well with digital controls, and is used in lamp dimmers, motor drives, audio amplifiers, computer power supplies and solar panel charge control. The switching frequency must be chosen with care for the application.