A device or a circuit which rectifies only one-half of each. cycle of an alternating voltage is called a half-wave rectifier.
Electric circuit : The alternating voltage to be rectified is applied across the primary coil (P1 P2) of a transformer. The secondary coil (S1 S2) of the transformer is connected in series with the junction diode and a load resistance R , as shown in below figure. The alternating voltage across the secondary coil is the ac input voltage Vi . The dc voltage across the load resistance is called the output voltage V0.
Working : Due to the alternating voltage Vir , the p-region of the diode becomes alternatively positive and negative with respect to the n-region.
During the half-cycle when the p-region is positive, the diode is forward biased and conducts. A current IL passes through the load resistance RL in the direction shown.
During the next half cycle, when the p-region is negative, the diode is reverse biased and the forward current drops to zero.
Thus, the diode conducts only during one-half of the input cycle and thus acts as a half-wave rectifier. The intermittent output voltage V0 has a fixed polarity but changes periodically with time between zero and a maximum value.
IL is unidirectional. Above figure shows the input and output voltage waveforms.
The pulsating dc output voltage of a halfwave rectifier has the same frequency as the input.
