Download - Lecture 02 Halfwave Rectifier
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EE
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112 Basic Electronics Dr. Faraz Akram
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EE
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112 Basic Electronics Dr. Faraz Akram
A rectifier is an electrical device that converts alternating
current (AC), to direct current (DC).
What is AC and DC? In direct current (DC), the current only flows in one direction.
In alternating current (AC), changes direction periodically.
Is house current AC or DC?
Name some devices that work on AC
Why we need to convert AC to DC?
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EE
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112 Basic Electronics Dr. Faraz Akram
Rectifiers are found in all DC power supplies that operate from an AC voltage
source.
DC power supply converts the standard 220 V, 50Hz ac voltage into a constant
dc voltage
220V, 50Hz
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112 Basic Electronics Dr. Faraz Akram
220V, 50Hz
In half wave rectification, the positive half of the ACwave is passed, while the other half is blocked.
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EE
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112 Basic Electronics Dr. Faraz Akram
Note: The diode
is considered to
be ideal.
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EE
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112 Basic Electronics Dr. Faraz Akram
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EE-112 Basic Electronics Dr. Faraz Akram
Example: What is the average value of the half-wave rectified
voltage in Figure
= =
=
2
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EE-112 Basic Electronics Dr. Faraz Akram
In the previous discussion, the diode was considered ideal. When
the practical diode model is used with the barrier potential of 0.7V
taken into account, this is what happens.
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EE-112 Basic Electronics Dr. Faraz Akram
Draw the output voltages of each rectifier for the indicated
input voltages.
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EE-112 Basic Electronics Dr. Faraz Akram
Thepeak inverse voltage (PIV) equals the peak value of theinput voltage, and the diode must be capable of withstanding
this amount of repetitive reverse voltage.
= ()
A diode should be
rated at least 20%
higher than the
PIV.
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EE-112 Basic Electronics Dr. Faraz Akram
A transformer is often used to couple the ac input voltage from
the source to the rectifier, as shown in Figure
Transformer coupling provides two advantages. First, it allows the source voltage to be stepped down as needed.
Second, the ac source is electrically isolated from the rectifier, thus
preventing a shock hazard in the secondary circuit.
Half wave rectifier with transformer
coupled input voltage
=
= 0.7
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EE-112 Basic Electronics Dr. Faraz Akram