RECTIFIERS
“Rectifiers are the circuit which converts ac to dc”
Rectifiers are grouped into tow categories depending on the period of conductions.
1. Half-wave rectifier
2. Full- wave rectifier.
Half-wave rectifier
The circuit diagram of a half-wave rectifier is shown in fig below along with the I/P and O/P waveforms.
Half wave rectifier (i) Circuit diagram (ii) waveforms
• The transformer is employed in order to step-down the supply voltage and also to prevent from shocks.
• The diode is used to rectify the a.c. signal while , the pulsating d.c. is taken across the load resistor RL.
• During the +ve half cycle, the end X of the secondary is +ve and end Y is -ve . Thus , forward biasing the diode. As the diode is forward biased, the current flows through the load RL and a voltage is developed across it.
• During the –ve half-cycle the end Y is +ve and end X is –ve thus, reverse biasing the diode. As the diode is reverse biased there is no flow of current through RL thereby the output voltage is zero.
Full-wave rectifier
Full-wave rectifier are of two types
1. Centre tapped full-wave rectifier
2. Bridge rectifier
Centre tapped full –wave rectifier
Centre tapped Full wave rectifier (i) Circuit diagram (ii) waveforms
• The circuit diagram of a center tapped full wave rectifier is shown in fig. 2.6 above. It employs two diodes and a center tap transformer. The a.c. signal to be rectified is applied to the primary of the transformer and the d.c. output is taken across the load RL.
• During the +ve half-cycle end X is +ve and end Y is –ve this makes diode D1 forward biased and thus a current i1 flows through it and load resistor RL.Diode D2 is reverse biased and the current i2 is zero.
• During the –ve half-cycle end Y is +Ve and end X is –Ve. Now diode D2 is forward biased and thus a current i2 flows through it and load resistor RL. Diode D1 is reversed and the current i1 = 0.
Disadvantages
• Since, each diode uses only one-half of the transformer secondary voltage the d.c. output is comparatively small.
• It is difficult to locate the center-tap on secondary winding of the transformer.
• The diodes used must have high Peak-inverse voltage.
Bridge rectifier
Full wave bridge wave rectifier (i) Circuit diagram (ii) waveforms.
• The circuit diagram of a bridge rectifer is shown above. It uses four diodes and a transformer.
• During the +ve half-cycle, end A is +ve and end B is –ve thus diodes D1 and D3 are forward bias while diodes D2 and D4 are reverse biased thus a current flows through diode D1, load RL ( C to D) and diode D3.
• During the –ve half-cycle, end B is +ve and end A is –ve thus diodes D2 and D4 are forward biased while the diodes D1 and D3 are reverse biased. Now the flow of current is through diode D4 load RL ( D to C) and diode D2. Thus, the waveform is same as in the case of center-tapped full wave rectifier.
Advantages
• The need for center-taped transformer is eliminated.
• The output is twice when compared to center-tapped full wave rectifier.
for the same secondary voltage.
• The peak inverse voltage is one-half(1/2) compared to center-tapped full wave rectifier.
• Can be used where large amount of power is required.
Disadvantages
• It requires four diodes.
• The use of two extra diodes cause an additional voltage drop thereby reducing the output voltage.
“Rectifiers are the circuit which converts ac to dc”
Rectifiers are grouped into tow categories depending on the period of conductions.
1. Half-wave rectifier
2. Full- wave rectifier.
Half-wave rectifier
The circuit diagram of a half-wave rectifier is shown in fig below along with the I/P and O/P waveforms.
Half wave rectifier (i) Circuit diagram (ii) waveforms
• The transformer is employed in order to step-down the supply voltage and also to prevent from shocks.
• The diode is used to rectify the a.c. signal while , the pulsating d.c. is taken across the load resistor RL.
• During the +ve half cycle, the end X of the secondary is +ve and end Y is -ve . Thus , forward biasing the diode. As the diode is forward biased, the current flows through the load RL and a voltage is developed across it.
• During the –ve half-cycle the end Y is +ve and end X is –ve thus, reverse biasing the diode. As the diode is reverse biased there is no flow of current through RL thereby the output voltage is zero.
Full-wave rectifier
Full-wave rectifier are of two types
1. Centre tapped full-wave rectifier
2. Bridge rectifier
Centre tapped full –wave rectifier
Centre tapped Full wave rectifier (i) Circuit diagram (ii) waveforms
• The circuit diagram of a center tapped full wave rectifier is shown in fig. 2.6 above. It employs two diodes and a center tap transformer. The a.c. signal to be rectified is applied to the primary of the transformer and the d.c. output is taken across the load RL.
• During the +ve half-cycle end X is +ve and end Y is –ve this makes diode D1 forward biased and thus a current i1 flows through it and load resistor RL.Diode D2 is reverse biased and the current i2 is zero.
• During the –ve half-cycle end Y is +Ve and end X is –Ve. Now diode D2 is forward biased and thus a current i2 flows through it and load resistor RL. Diode D1 is reversed and the current i1 = 0.
Disadvantages
• Since, each diode uses only one-half of the transformer secondary voltage the d.c. output is comparatively small.
• It is difficult to locate the center-tap on secondary winding of the transformer.
• The diodes used must have high Peak-inverse voltage.
Bridge rectifier
Full wave bridge wave rectifier (i) Circuit diagram (ii) waveforms.
• The circuit diagram of a bridge rectifer is shown above. It uses four diodes and a transformer.
• During the +ve half-cycle, end A is +ve and end B is –ve thus diodes D1 and D3 are forward bias while diodes D2 and D4 are reverse biased thus a current flows through diode D1, load RL ( C to D) and diode D3.
• During the –ve half-cycle, end B is +ve and end A is –ve thus diodes D2 and D4 are forward biased while the diodes D1 and D3 are reverse biased. Now the flow of current is through diode D4 load RL ( D to C) and diode D2. Thus, the waveform is same as in the case of center-tapped full wave rectifier.
Advantages
• The need for center-taped transformer is eliminated.
• The output is twice when compared to center-tapped full wave rectifier.
for the same secondary voltage.
• The peak inverse voltage is one-half(1/2) compared to center-tapped full wave rectifier.
• Can be used where large amount of power is required.
Disadvantages
• It requires four diodes.
• The use of two extra diodes cause an additional voltage drop thereby reducing the output voltage.
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