In many industrial applications, it is required to convert a fixed-voltage dc source into a variable voltage dc source. A dc chopper converts directly from dc to dc and is also known as a dc-to-dc converter. A chopper can be considered as dc equivalent to an ac transformer with a continuously variable turn's ratio. Like a transformer, it can be used to step-down or step-up a dc voltage source. Choppers are widely used for traction motor control in electric automobiles. They provide smooth acceleration control, high efficiency and fast dynamic response.