The closest thing to a linear dc-dc power supply would be a dc motor driving a dc generator, which isn’t a very efficient proposition.

Despite being viable for a lot of the same applications, the difference between brush dc motors and brushless dc motors are not subtle.

Typically, engineers can choose between direct-current (DC) or alternating-current (AC) motors. Machine Design has covered the difference between basic types of motors in the past.

When energy-efficiency costs come into play, more designers are opting for the electronically commutated motor rather than familiar AC and DC versions.