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The left hand waveform
shows the input voltage
(50 Hz AC in the UK).
The voltages at points A
and B on the transformer
are changing in opposite
directions.
When A is increasing in
a positive direction, B
is increasing
negatively.
It is like the opposite
ends of a see-saw.
During the first half
cycle, A is positive and
B is negative.
D1 has positive on its
anode, D2 has negative
on its cathode.
Both are forward biased.
Current flows around the
circuit formed by these
diodes, the load and the
transformer winding, as
shown in the second
diagram.
The current flowing up
through the load
produces a pulse of
voltage across the load
as shown in the right
hand waveform.
During the next half
cycle, A is negative and
B is positive.
D4 has positive on its
anode, D3 has negative
on its cathode.
Both are forward biased.
Current flows around the
circuit as shown in the
bottom diagram, again
flowing in the same
direction through the
load and producing
another pulse of
voltage.
Since the full cycle is
used this circuit is
called a FULL-WAVE
rectifier.
Since there are two
pulses for each cycle of
input, there are 100
pulses per second out
(in the UK).
The pulsating DC can be
smoothed with a
reservoir capacitor, as
in the half-wave
rectifier circuit.
Since the pulse
frequency is higher than
that of the half-wave
rectifier, it is easier
to smooth.
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