Rectifier diodes are electronic devices that allow electrical current to flow in one direction only. Because of this electrical property, diodes are used to convert alternating current electrical energy into direct current electrical energy. In an automotive electrical system, diodes can be found in several places, including the alternator. Alternator diodes perform three critical functions for the automotive charging system.

Conversion from AC to DC Power

An alternator converts mechanical energy into electrical energy by creating a variable electromagnetic field. This field is induced across alternator windings, and creates an alternating current signal. However, the electrical devices in a car require direct current electrical energy. The electrical energy passes through a device called a rectifier, which is made up of six or more diodes. The rectifier converts the alternating current energy produced by the alternator into direct current energy the automobile can use.