DC

A DC-to-DC converter is an electronic circuit or electromechanical device that converts a source of direct current from one voltage level to another. It is a type of electric power converter. Power levels range from very low to very high.
Before the development of power semiconductors, one way to convert the voltage of a DC supply to a higher voltage, for low-power applications, was to convert it to AC by using a vibrator, then by a step-up transformer, and finally a rectifier. Where higher power was needed, a motor–generator unit was often used, in which an electric motor drove a generator that produced the desired voltage. These relatively inefficient and expensive designs were used only when there was no alternative, as to power a car radio that require much higher voltages than available from a 6 or 12 V car battery)....