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.

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

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.

DC motors and AC motors accomplish this task in different ways. DC machines can be classified as self-excited, separately excited, permanent magnet (PM), and brushless.