Circuits that are used to convert the Alternating Current (AC) input power into a Direct Current (DC) output power is known as rectifier circuits. Rectifiers are found in almost all equipment, from a low voltage battery charger to High Voltage DC transmission systems. Basically, rectifiers are classified into Controlled rectifiers and uncontrolled rectifiers. In controlled rectifiers, semiconductor switches such as thyristors, BJTs, MOSFETs, IGBT etc are used. The output parameters of a controlled rectifier can be easily controlled with the help of semiconductor switches. In this article only the uncontrolled rectifiers are discussed. As the name indicates these rectifiers cannot be controlled externally. Controlled rectifiers are made up of a few diodes and conditioning elements such as capacitors.