RECTIFIER CIRCUITS USING PN JUNCTION DIODES

admin January 18, 2011 2 Comments

AIM

To implement the half wave rectifier and full wave rectifier using 1N 4007 diode

COMPONENTS AND EQUIPMENTS REQUIRED


1. Diodes

2. Centre tap transformer

3. Resistors

4. CRO

CIRCUIT DIAGRAM

HALF WAVE RECTIFIER

FULL WAVE CENTRE TAP RECIFIER

FULL WAVE BRIDGE RECTIFIER

WAVEFORMS

HALF WAVE RECTIFIER WITHOUT CAPACITOR FILTER

WITH CAPACITOR FILTER

FULL WAVE RECTIFIER WITHOUT CAPACITOR FILTER

FULL WAVE RECTIFIER WITH CAPACITOR FILTER

THEORY

A diode is using to pass current in a single direction. Alternating current is a current which flows in both directions. In some applications we need dc power supply. A method to obtain dc supply is by using batteries. But it is not economical at all times. It is possible to obtain dc from ac supply .That process is known as rectification. Rectification is of two types: 1.half wave rectification 2.full wave rectification

HALF WAVE RECTIFIERS

In a half wave rectifier only one half cycle of ac voltage is taking. The circuit is given. Here only one diode is using. During the positive half cycle of ac voltage the diode conducts. So current flows through load. During the negative half cycle, the diode is reverse biased .So no current flows through the diode. This type of rectification needs only one diode. But the efficiency is not so good as that of full wave rectifier

FULL WAVE RECTIFIERS

Unlike a half wave rectifier, a full wave rectifier conducts in both half cycles of ac voltage.

A full wave rectifier can be implemented in two ways

a) Full wave bridge rectifier

In full wave bridge rectifiers 4 diodes are using. During positive half cycle, D1 and D4 are in forward biased condition. In the negative half cycle of ac D3 and D2 are in forward biased condition. So in both the half cycles current through the load is in single direction. Thus rectification can be done. This circuit does not need a centre tap rectifier. But it requires more number of diodes than centre tap and half wave rectifiers.

b) Full wave centre tap rectifier

This is another method to obtain full wave rectification. In this method only two diodes are using. But it requires a center tap transformer. During the positive half cycle diode D1 conducts. In the negative half cycle diode D2 conducts. So in both half cycles current flowing through load in same direction. Thus rectification can be obtained.

PROCEDURE

1. Test the devices before wiring.

2. Wire up the half wave rectifier circuit

3. Apply the sine wave from the transformer secondary.

4. Plot the wave forms

5. Repeat the same steps for full wave rectifiers

RESULT

Rectifier circuits using 1N 4001 diode were implemented and wave forms were plotted.

SAMPLE VIVA QUESTIONS

1. What is a half wave rectifier?

In a half wave rectifier only one half cycle of ac voltage is taking. The circuit is given. Here only one diode is using. During the positive half cycle of ac voltage the diode conducts. So current flows through load. During the negative half cycle, the diode is reverse biased .So no current flows through the diode. This type of rectification needs only one diode. But the efficiency is not so good as that of full wave rectifier

2. What is a full wave rectifier?

Unlike a half wave rectifier, a full wave rectifier conducts in both half cycles of ac voltage. So output gets in both the half cycles.

3. What are the two schemes of full wave rectifiers?

1. Centre tap rectifier

2. Bridge rectifier

4. What are the advantages of bridge rectifier over center tap rectifier?

It does not need a centre tap transformer

5. What is the disadvantage of bridge rectifier over centre tap rectifier?

4 diodes are needed.

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