A rectifier
is a device that causes a great current to flow in one direction of the applied
voltage than the other.
The differences between rectifiers can be summarized
as follows by comparing their mode of current rectification.
In a half wave rectification, the rectifier
conduct current only during the positive half cycle of the input a.c supply. The native half cycle of a.c supply are
suppressed, i.e during the negative half cycle no current is conducted and
hence no voltage appears across the load. Current only flow in one direction of
the applied voltage through the load after every half cycle.
in a half wave rectifier circuit, the a.c
voltage across the windings changes potentials after every half cycle , during
the positive half cycle of input a.c voltage , end say A, becomes positive with respect to end say B ,
this makes the diodes forward biased and hence it conduct current. During the
negative half cycle, end A is negative with respect to end B, under this
conditions the diode is reversed biased and it conduct the diode is reversed
biased and it conduct no current. Therefore current flow through the diode
during the positive half cycle of input a.c only, it is blocked during the
negative half cycle. In this way, current flow through the circuit always in
one direction.
While in full-wave
rectification, current flows through the load in the same direction for both
the half cycles of and input a.c voltage. This can be achieved by two or more
diode working alternatively; center tap full wave rectifier and bridge
rectifier are the most common type used.
let us now consider a center tap full wave rectifier, the circuit employ two diode, a center tap secondary
windings is used with two diodes connected so that each uses only half cycles
of input a.c voltage . In other words, diode D1, the 1st diode
utilizes the a.c voltage appearing across the upper half of secondary windings
for rectification while the 2nd diode D2, used the lower half
winding.
during the
positive the positive half cycle of secondary voltage the end say A of the secondary windings becomes positive and end say B
becomes negative, this makes the first diode D1 forward biased and the 2nd
diode D2 reversed biased.
Therefore diode D1 conduct while diode D2 does
not. the conventional current flow in through the diode D1 , the load resistor and
upper half of secondary windings.
during the negative half cycle, end A of the secondary
windings becomes negative and end B positive . therefore diode D2, conduct
while diode D1 does not. the current
flow in through the diode D2, load resistor and lower half winding.
the current in the load is in the same direction
in both the half cycles.
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