Question

Draw the circuit diagram of a full wave rectifier and explain its working. Also, give the input and output waveforms.

Answer 1

Full wave rectifier



A full wave rectifier consists of two diodes connected in parallel across the ends of secondary winding of a centre tapped step down transformer. The load resistance $R_L$ is connected across secondary winding and the diodes between $A$ and $B$ as shown in the circuit.

During positive half cycle of input a.c., end $A$ of the secondary winding becomes positive and end $B$ negative. Thus, diode $D_1$ becomes forward biased, whereas diode $D_2$ reverse biased. So, diode $D_1$ allows the current to flow through it, while diode $D_2$ does not, and current in the circuit flows from $D_1$ and through load $R_L$ from $X$ to $Y$.

During negative half cycle of input a.c., end $A$ of the secondary winding becomes negative and end $B$ positive, thus diode $D_1$ becomes reverse biased, whereas diode $D_2$ forward biased. So, diode $D_1$ does not allow the current to flow through it but diode $D_2$ does, and current in the circuit flows from $D_2$ and through load $R_L$ from $X$ to $Y$.



Since, in both the half cycles of input a.c., electric current through load $R_L$ flows in the same direction, so d.c. is obtained across $R_L$. Although the direction of electric current through $R_L$ remains same, but its magnitude changes with time, so it is called pulsating d.c.