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7/31/2019 (05) Rectifiers
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Rectifiers 1, 16 2012
Thought of the Day
Soon or late,
the man who wins
is the man
WHO THINKS HE CAN !
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Diode Rectifiers
D.C. Kulshreshtha
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Block Diagram ofDC Power Supply
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Diodes in Rectifier Circuits
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Half-wave Rectifier
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Full-wave Rectifier(Centre-tap)
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Full-wave Rectifier(Bridge)
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Diode Ratings
1. Current Handling Capacity.2. Peak Inverse Voltage (PIV):It is the
largest reverse voltage that is expected
to appear across the diode. Usually,diodes are selected which have VZat
least 50 % greater than PIV.
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PIVRatings
For half-wave rectifier : Vm
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Figures of Merit of a Rectifier1. Ripple Factor (r) :
2. Rectification Efficiency () :
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Performance of Half-wave Rectifier
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Total RMS Value :
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RMS Value of AC Components :
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Note that this is a general result. Now, for
Half-wave Rectifier :
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Performance of Full-wave Rectifier
Its period is , and not 2.How much is its period in terms oft?
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Total RMS Value :
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Ripple Factor :
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Rectification Efficiency :
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Filter Circuits
The output of a rectifier is not purely dc.It also has some ac components, calledripples.
The ripples are maximum in half-wave
rectifier, and are less in full-wave rectifier
Filter circuit converts pulsating output of arectifier into a steady dc level.
Filters simply smoothen out the ripples.
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There are two ways to do it :
1. Ripples are bypassed around a theload by using a shunt capacitor.
2. Ripples can be limited to a low value
by a series inductor. A filter circuit is generally a
combination of capacitors and
inductors.
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Filtering action depends upon the fact
that:Capacitor allows ac only to pass.
Inductor allow dc only to pass.
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Shunt Capacitor Filter
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Operation of Capacitor Filter
During the conduction period, thecapacitor gets charged and stores energy.
During the non-conduction period, the
capacitor discharges through the loadresistance delivering energy to it.
Capacitor gets charged to the peak valuequickly because charging time constant isalmost zero.
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Discharging time constant is quite large,because it discharges through the load
resistance.
As XC
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Obviously, a large-value capacitor shouldbe preferred.
Any disadvantage ?
Ans . : Yes. Diode may get damaged.
How does the ripple factor vary with
increase in the load current ?
Ans. : Increases.
Review
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Review Block Diagram of
DC Power Supply. Half-wave Rectifier.
Full-wave Rectifier(Centre-tap).
Full-wave Rectifier(Bridge).
Diode Ratings.1. Current Handling
Capacity.2. PIVRatings.
Figures of Merit of aRectifier :1. Ripple Factor.
2. Rectification Efficiency.
Performance of Half-
wave Rectifier.Idc, Irms, Irms, r,
Performance of Full-wave Rectifier.
Idc, Irms, Irms, r, Filters.