Centre-Tap Full-Wave Rectifier
Centre-Tap Full-Wave Rectifier:
In such a rectifier, the ac input is applied through a transformer, the anodes of the two diodes D1 and D2 (having similar characteristics) are connected to the opposite ends of the centre tapped secondary winding and two cathodes are connected to each other and are connected also through the load resistance RL and back to the centre of the transformer, as shown.
When the top of the transformer secondary winding is positive, say during the first half-cycle of the supply, the anode of diode D1 is positive w.r.t. cathode, and anode of diode D2 is negative w.r.t. cathode. Thus only diode D1 conducts, being forward biased and current flows from cathode to anode of diode D1 through load resistance RL and top half the transformer secondary making cathode end of load resistance RL positive. During the second half-cycle of the input voltage the polarity is reversed, making the bottom of the secondary winding positive w.r.t. centre tap and thus diode D2 is forward biased and diode D1 is reverse biased. Consequently during this half-cycle of the input only the diode D2 conducts and current flows through the load resistance RL and bottom of the transformer secondary making the cathode end of the load resistance RL positive. Thus the direction of flow of current through the load resistance RL remains the same during both halves of the input/supply voltage. Thus the circuit shown acts as a full-wave rectifier.