Rectifiers are the electronics circuits which convert AC voltage into DC voltage and the process of conversion of AC voltage into DC voltage is known as rectification.
Generally, there are two types of rectification processes i.e. half wave rectification and full wave rectification and on the basis of rectification there are two types of rectifiers i.e. Half Wave Rectifier and Full Wave Rectifier.
In this particular article, we will try to elaborate each and
every concept about Full Wave Rectifiers. If any aspect is not there, please
feel free to provide feedback in the comment section.
Full Wave Rectifier
A Full Wave Rectifier is the
type of rectifier circuit which offers full wave rectification. Full wave
rectification means the conversion of the full waveform for AC signal into a
pulsating DC signal.
Circuit Diagram of Full Wave Rectifier
For the efficient conversion of
full waveform of AC input signal into DC signal, a full wave rectifier circuit
uses two types of configurations.
In the first configuration, a full wave rectifier circuit is designed by using two one-way switches (like Diode, SCR, MOSFET etc.) and a centre tapped transformer. As this circuit uses a centre tapped transformer, this circuit is also known as centre tapped full wave rectifier. The circuit diagram for centre tapped full wave rectifier is shown in the given figure.
In the given figure, we see that
S1 and S2 are the two switches which are connected in the same orientation with
the terminal A and B of the secondary of the transformer. And the load is
connected between the other terminals of the switches and the secondary of the
transformer with the help of tapping, as the name indicates it is tapped at the
centre of the secondary of the transformer.
In the second configuration, a
full wave rectifier circuit is designed by using four one-way switches which
are connected in a bridge-like arrangement in the same orientation. As, in this
type of circuit switches are connected in bridge-like arrangement, this type of
circuit is also known as full wave bridge rectifier. The circuit diagram
for full wave bridge rectifiers shows in the given figure.
In the given figure we see that
S1, S2, S3, and S4 are the four switches which are connected across the sides
of the square in the same orientation. This square shape arrangement is
referred to as a bridge. In the bridge rectifier circuit, the AC supply is
given to the two opposite corners of the bridge (A and C) and the load is
connected with the other two opposite corners of the bridge (B and D).
Note:- Here orientation means, the
anode and cathode of the switches are connected in the same manner.
Full Wave Rectifier Working
As we discussed that there are two types of full wave rectifier configurations i.e. Centre Tapped Full Wave Rectifier and Full Wave Bridge Rectifier. Let us understand the working of these two types of full wave rectifiers separately in detail.
To make it
easy to understand, we assumed that the switches used in the above circuits are
ideal. By ideal we mean that the forward voltage drop and the reverse recovery
time of the switches are negligible.
Centre Tapped Full Wave Rectifier
As we
discussed above, a full wave rectifier which is designed by using two switches
and a centre tapped transformer is known as centre tapped full wave rectifier.
The circuit diagram of the centre tapped full wave rectifier is shown above in
the full wave rectifier circuit diagram section.
Let us say
Vs = Vm . sin(ωt) is the voltage applied to the primary
winding of the transformer and the turns ratio of the transformer is 1:2, so
that when the load is tapped at the centre of the secondary winding then the
turns ratio of each half winding and primary winding is 1:1.
So, in this rectifier circuit, when the positive half of AC waveform is given then the terminal A is positive with respect to B, as a result switch S1 is forward biased and it conducts and the switch S2 is reversed biased and it does not conduct. In this case switch S2 experiences an inverse voltage of 2Vs. (discussed in detail in the separate article regarding centre tapped rectifier). In this case the current flows through the switch S1 and the load which is tapped at the centre of the secondary winding of the transformer as shown in the given figure by the red line.
Similarly, if the
negative half of the AC voltage is given then the switch S2 conducts and S1
does not conduct. In this case the current flows through the switch S2 and the
load which is tapped at the centre of the secondary winding of the transformer
as shown in the given figure by the green line and the switch S1 experiences an
inverse voltage of 2Vs.
Full Wave Bridge Rectifier
As we
discussed above, a full wave rectifier which is designed by using four switches
like Diode, SCR, MOSFET etc. which are connected in a bridge-like arrangement
is known as full wave bridge rectifier. The circuit diagram of the full wave
bridge rectifier is shown in the full wave rectifier circuit diagram
section.
In the
bridge rectifier circuit two diagonally opposite switches conduct for one half
of the AC supply and the other two diagonally opposite switches conduct for the
other half of the AC supply. In this particular bridge rectifier switch S1 and
S3 conduct for the positive half of the AC supply and the direction of flow of
current is shown by the red lines in the given figure.
For the negative half cycle switch S2 and S4 conduct and the direction of flow of current in this condition is shown by green lines in the given figure.
The full wave bridge rectifier is preferably used over centre tapped full wave rectifier circuits in modern electronics due to some advantages. These advantages are listed below.
Advantages of Bridge Rectifier
- The centre tapped rectifier circuit uses a centre tapped transformer this centre tapped transformer is quite expensive, hence the centre tapped rectifier circuit is costlier than the bridge rectifier circuit, that's why the bridge rectifier circuit is preferably used over the centre tapped rectifier circuit.
- The centre tap transformer is large in size, as a result the centre tapped rectifier is bulkier as compared to the bridge rectifier circuit.
- The switches used in centre tapped rectifier circuit have high Peak Inverse voltage and the high PIV switches are expensive as compared to low PIV switches, that's why a bridge rectifier circuit is preferably used over the centre tapped rectifier circuit.
Types of Full Wave Rectifier
On the
basis of circuit configuration there are two types of full wave rectifiers i.e.
Full Wave Bridge Rectifier and Centre Tapped Full Wave
Rectifier. The circuit diagram, working, advantages, disadvantages and
other concepts of these circuits are discussed in the above sections.
On the
basis of the switch used or controlling the output voltage, a full wave
rectifier can be further classified into three types.
- Uncontrolled Full Wave Rectifier
- Half-Controlled Full Wave Rectifier / Semiconverter
- Controlled Full Wave Rectifier / Full Converter
Uncontrolled
Full Wave Rectifier
A full wave rectifier circuit which is designed by using only diodes
(uncontrolled switch) is known as uncontrolled full wave rectifier. Ex diode bridge rectifier and centre tapped rectifier using diode. In this type of
rectifier, we cannot control the DC output voltage.
Half-Controlled Full Wave Rectifier
This type
of full wave rectifier can be designed by using the combination of diode
(uncontrolled switch) and SCR (half-controlled switch). In this type of
rectifiers, we have limited control over the DC output voltage hence this type
of rectifier is also known as semi-converter.
Semi
converters offer one quadrant operation means, in semi converters we cannot get
negative DC output voltage, consequently this rectifier cannot be operated as
an inverter.
Controlled Full Wave Rectifier
As the name
implies controlled full wave rectifier, in this type of rectifier we have
complete control over the DC output voltage. This type of rectifier circuit can
be designed by using SCR (half-controlled switch) or MOSFET (controlled switch)
or any other half controlled or controlled switch. This type of rectifier is
also known as full converters.
Full
converters offer two quadrants operation means, in full converter we can also
get negative DC output voltage, consequently, a full Wave controlled rectifier
can be worked as an inverter.
Advantages of Full Wave Rectifier
- In case of full wave rectifier circuit, the full waveform of AC input supply is converted into pulsating DC, whereas in the case of half rectifier only half waveform of the AC input supply is utilised and the other half is wasted. Hence, the full wave rectifier circuits are more efficient than the half wave rectifier circuits.
- In case of a full wave rectifier circuit the ripple in output voltage is less as compared to half wave rectifier circuit. Hence, less filtering requirements in full wave rectifier circuits.
- A full wave-controlled rectifier circuit can work as an inverter, whereas the half wave rectifier circuit cannot.
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