Question

Explain the working of a half wave diode rectifier.

Answer 1

Half Wave Rectifier: A circuit which rectifies half of the a.c. wave is called half wave rectifier.
Figure shows the circuit for half wave rectification. The a.c. voltage $\left(V_S\right)$ to be rectified is obtained across the secondary ends of the transformer. The $P$-end of the diode $D$ is connected to $S_1$ of the secondary coil of the transformer.
The $N$-end of the diode is connected to the other end $S_2$ of the secondary coil of the transformer, through a load resistance $R_L$. The rectified output voltage $V_{dc}$ appears across the load resistance $R_L$.
During the positive half cycle of the input a.c. voltage $V_S$, $S_1$ will be positive and the diode is forward biased and hence it conducts.
Therefore, current flows through the circuit and there is a voltage drop across $R_L$. This gives the output voltage as shown in Figure.
During the negative half cycle of the input a.c. voltage $\left(V_S\right)$, $S_1$ will be negative and the diode $D$ is reverse biased. Hence the diode does not conduct. No current flows through the circuit and the voltage drop across $R_L$ will be zero. Hence no output voltage is obtained. Thus corresponding to an alternating input signal, unidirectional pulsating output is obtained.
The ratio of d.c. power output to the a.c. power input is known as rectifier efficiency. The efficiency of half wave rectifier is approximately $40.6$%.