A rectifier is an electronic device that converts alternating current (AC) into direct current (DC) by allowing current to flow through the device in one direction only. The process of converting AC to DC is called rectification. Rectifiers are made up of one or more diodes, which act as one-way valves to maintain the flow of current in a single direction. There are several types of rectifiers, including:

• Half-wave rectifier: Allows only one half of an AC waveform to pass through to the load.
• Full-wave rectifier: Converts both half-cycles of the AC voltage waveform to an unbroken series of voltage pulses of the same polarity.
• Uncontrolled rectifier: A type of rectifier whose voltage cannot be controlled.
• Controlled rectifier: A type of rectifier whose voltage can be controlled.

Rectifiers have many uses, but they are most commonly found as components of DC power supplies and high-voltage direct current power transmission systems. They are also used in electric welding to provide polarized voltage, as signal peak detectors in AM radio, and in gas heating systems to detect the presence of a flame.