Rectifiers
are the electronic circuits that 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
article, we will try to elaborate some important concepts about full wave
rectifiers.
What is Full Wave Rectifier?
A full wave
rectifier is the type of rectifier circuit which offers full wave
rectification, means the conversion of the full waveform of the AC signal into
a pulsating DC signal.
As they
utilize both halves of the AC waveforms to convert into pulsating DC, unlike
the half wave rectifiers which utilizes only one half of the AC waveform. These
rectifiers provide improved efficiency as compared to half wave rectifiers.
Therefore, these rectifiers are preferred over half wave rectifiers.
Circuit Diagram of Full Wave Rectifier
For the
efficient conversion of full waveform of AC input signal into pulsating DC
signal, a full wave rectifier circuit uses two types of configurations i.e. center
tapped full wave rectifier and full wave bridge rectifier.
Center Tapped Full Wave Rectifier
In this type of full wave rectifier circuit configuration, two
one-way semiconductor switches, such as diodes SCRs, MOSFETs etc. and a center tapped transformer are connected as shown in the given figure. The name “center
tapped” derives from the application of a center tapped transformer.
Full Wave Bridge Rectifier
In this
type of full wave rectifier circuit configuration, four one-way semiconductor
switches are connected in a bridge-like arrangement in the same orientation as
shown in the given figure.
Full Wave Rectifier Working
We have created separate articles for the Center Tapped Full Wave Rectifier and Full Wave Bridge Rectifier. In these articles, we discuss their
circuit diagrams, working principles, output waveforms, formulas and other
important concepts.
Types of Full Wave Rectifier
As discussed above there are two types of full wave rectifier circuit configuration i.e. Full Wave Bridge Rectifier and Centre Tapped Full Wave Rectifier. These rectifier circuits can be designed by using any semiconductor switches that have unidirectional current conduction property. In power electronics these semiconductor switches are categorized as controlled switches and uncontrolled switches. The type of switches used determine the controlling nature of the rectifier circuit.
So, on the basis of the switch used or controlling the output voltage, full wave rectifiers can be further classified into three types.
- Uncontrolled Full Wave Rectifier
- Half-Controlled Full Wave Rectifier or Semi-Converter
- Controlled Full Wave Rectifier or Full Converter
Uncontrolled
Full Wave Rectifier
A
full wave rectifier circuit which is designed by using only uncontrolled
switches such as diodes is known as uncontrolled full wave rectifier. This
type of rectifier provides a fixed DC output voltage from a fixed AC input
voltage. ex. Diode Bridge Rectifier
Half-Controlled Full Wave Rectifier or Semi-converter
This
type of full wave rectifier can be designed by using the combination of both
uncontrolled switches, such as diodes, and controlled switches, such as SCRs.
This type of rectifier provides variable DC output voltage from fixed AC input
voltage. However, in this type of rectifiers, we have limited control over the
DC output voltage, which is why they are known as the half-controlled full
wave rectifiers or semi-converter.
By
“limited control”, we mean that they only provide constant (positive) polarity
DC voltage. Since the direction of current flow remains the same throughout the
operation of the rectifier means the current is also positive therefore, they
provide only one quadrant operation. This property would not allow these
rectifiers to work as an inverter. However, as a converter they have better
performance than controlled full wave rectifiers or full converters.
Controlled Full Wave Rectifier or Full Converter
As
the name implies controlled full wave rectifiers, in this type of rectifier we
have complete control over the DC output voltage. This type of rectifier
circuit can be designed by using only controlled switches.
By
“complete control”, we mean that we can get the both negative and the positive
average output voltages. Since the direction of current flow remains the same
throughout the operation of the rectifier means the current is positive
therefore, these rectifiers provide two quadrant operation. This property
allows these rectifiers to work as an inverter while charging the battery
(under certain conditions).
Why is Full Wave Rectifier better than Half Wave Rectifier?
Full
wave rectifiers have certain listed advantages over half wave rectifiers, due
to which they are preferably used over half wave rectifiers.
- A full wave rectifier converts the full waveform of AC input supply into pulsating DC, whereas a half rectifier converts only half waveform of the AC input supply into DC pulsating with the other half being wasted. Consequently, the full wave rectifiers are more efficient than the half wave rectifiers. Generally, the maximum efficiency of full wave rectifiers is 81.2% which is almost double as that of half wave rectifiers (This proposed efficiency is the maximum efficiency for full wave rectifiers using diodes under ideal condition, it may vary depending on the switches used, load and other various factors).
- In the case of a full wave rectifier circuit, the ripple in output voltage is less as compared to half wave rectifier circuit. Less ripple means a smoother DC waveform. Hence, in full wave rectifier circuits filtering requirements are less.
- A full wave-controlled rectifier circuit can work as an inverter while charging a battery, whereas the half wave rectifier circuit cannot.
Disadvantages of Full Wave Rectifier
- Full wave rectifier circuits require more components as compared to half wave rectifiers such as a center tapped rectifier circuit requires a center tapped transformer and a bridge rectifier circuit requires more number of switches Therefore, full wave rectifier circuits are costlier than half wave rectifier circuits.
- In bridge rectifiers, two switches conduct the current at time, whereas in half wave rectifiers, only one switch conducts the current. As a result, the forward voltage drop in bridge rectifiers is twice as compared to half wave rectifiers.
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