Bridge Rectifier

Bridge Rectifier

During the positive half cycle of the input ac, A becomes +ve and B becomes -ve. Hence the diode D1 and D3 becomes forward biased and D2 and D4 becomes reverse biased. Hence D1 & D3 act as short circuit and D2 & D4 act as open circuit. The current flows through the load resistor R in the direction A-D1-a-b-D3-B.

During the negative half cycle of the input ac, A becomes -ve and B becomes +ve. Hence the diode D2 and D4 becomes forward biased and D1 and D3 becomes reverse biased. Hence D2 & D4 act as short circuit and D1 & D3 act as open circuit. The current flows through the load resistor R in the direction B-D2-a-b-D4-A.

It can be seen that both during +ve half cycle and -ve half cycle, the current through the load resistor R flows from a to b. Hence output voltage will be always positive

Here all the diodes are assumed as ideal ones. 

If silicon diodes are used the maximum output voltage will be reduced to Vm-1.2 Volt. ie 0.6 V will be dropped across two diodes in each half cycle (0.6 + 0.6 )

Center Tap Full Wave Rectifier

Full Wave Rectifier

There are two types of Full wave rectifiers

• Center Tap Full wave rectifier
• Bridge Rectifier 

Center Tap Full Wave Rectifier

The center tap transformer split the primary input ac signal into two equal but opposite phase ac signals. 

During the +ve half cycle of the input ac, the diode D1 is forward biased and diode D2 is reverse biased. Hence D1 will conduct and D2 will not conduct. The current flows in the direction D1 - RL - Ground. 

During the -ve half cycle of the input ac, the diode D2 is forward biased and diode D1 is reverse biased. Hence D2 will conduct and D1 will not conduct. The current flows in the direction D2 - RL - Ground. 

It can be seen that in both the half cycles the output current flows through the load resistor RL in the same direction and hence the circuit is working as a full wave rectifier.

The PIV of this rectifier is 2Vm   (Vm is the maximum secondary voltage induced)

Output frequency = 2fin  Twice that of input frequency

Rectifiers

Rectifiers

Rectifier is an electronic circuit that converts an alternating current/voltage (AC) into a direct current/voltage (DC).

There are two types of rectifiers a) Half Wave rectifier     b) Full Wave Rectifier

Half Wave rectifier

The above circuit diagram represents a half wave rectifier. It consists of a step down transformer, a diode and a load resistor.

Working

During the positive half cycle of the input AC, the secondary of the step down transformer A becomes +ve and B becomes -ve. This will make the diode forward biased and will allow the current flow. The current flows from A to X to Y to B. If the diode is an ideal diode the maximum output voltage will be Vm. If the diode is a silicon make, the maximum output voltage will be Vm - 0.7; where 0.7 is the cut-in voltage of silicon diode.

During the negative half cycle of the input AC, A becomes -ve, B becomes +ve and the diode becomes reverse biased. No current flows through the diode and hence output voltage will be zero.

Welcome

Welcome to My Blog on Electronic circuits