As discussed above the purpose of the rectifier is to convert the incoming ac from a transformer or other ac source to some form of pulsating dc. That it is it takes current that flows alternately in both directions and modifies it so that the output current flows only in one direction. All rectifier circuits may be classified into one of two categories as follows:
Half Wave Rectifiers : An easy way to convert ac to pulsating de is to simply allow half of the ac cycle to pass while blocking current to prevent it from flowing during the other half cycle. Because these circuits operate on the entire incoming ac wave they are known as half wave rectifiers.
Full Wave Rectifiers : The more common approach is to manipulate the incoming ac wave so that both halves are used to cause output current to flow in the same direction. Because these circuits operate on the entire incoming ac wave they are known as full wave rectifiers.