Question
State the principle of working of p-n diode as a rectifier. Explain, with help of a circuit diagram, the use of p-n diode as a full wave rectifier. Draw a sketch of the input and output waveforms.
Solution
Principle of rectifier:
The rectifier is a device that is capable of converting an alternating current into a unidirectional or pulsating form of direct current.
The process of conversion of alternating currents into direct currents is known as rectification.
Circuit diagram for a full wave rectifier:
Working of a rectifier:
1. A full wave rectifier uses two diodes and gives the rectified output voltage corresponding to both the positive and negative half-cycle of alternating current.
2. The p-side of the two diodes are connected to the ends of the secondary of the transformer and, the n-sides of the diodes are connected together.
3. Output is taken from between the common-point of the two diodes and secondary of the transformer. Hence, the secondary of the transformer is provided with center tapping and is also called the centre-tap transformer.
4. Let, the input voltage to A with respect to the centre be positive and, at the same instant, voltage at B being out-of-phase will be negative. Therefore, diode D1 is forward biased and starts conducting whereas, D2 being reverse biased does not conduct.
5. Thus, we get an output current and a output voltage across the load resistance RL in the first positive half-cycle.
6. During the course of the negative half - cycle, that is, when voltage at A becomes negative and voltage at B becomes positive, We will have D1 as reverse biased and D2 forward biased.
7. In the negative part of the cycle, only diode D2 will conduct giving an output current and output voltage across RL.
8. For both positive and negative half cycle we will get the output voltage. This rectified output voltage has the shape of half sinusoids.
Input and output waveforms:
The rectifier is a device that is capable of converting an alternating current into a unidirectional or pulsating form of direct current.
The process of conversion of alternating currents into direct currents is known as rectification.
Circuit diagram for a full wave rectifier:
Working of a rectifier:
1. A full wave rectifier uses two diodes and gives the rectified output voltage corresponding to both the positive and negative half-cycle of alternating current.
2. The p-side of the two diodes are connected to the ends of the secondary of the transformer and, the n-sides of the diodes are connected together.
3. Output is taken from between the common-point of the two diodes and secondary of the transformer. Hence, the secondary of the transformer is provided with center tapping and is also called the centre-tap transformer.
4. Let, the input voltage to A with respect to the centre be positive and, at the same instant, voltage at B being out-of-phase will be negative. Therefore, diode D1 is forward biased and starts conducting whereas, D2 being reverse biased does not conduct.
5. Thus, we get an output current and a output voltage across the load resistance RL in the first positive half-cycle.
6. During the course of the negative half - cycle, that is, when voltage at A becomes negative and voltage at B becomes positive, We will have D1 as reverse biased and D2 forward biased.
7. In the negative part of the cycle, only diode D2 will conduct giving an output current and output voltage across RL.
8. For both positive and negative half cycle we will get the output voltage. This rectified output voltage has the shape of half sinusoids.
Input and output waveforms:
