(05) rectifiers

7/31/2019 (05) Rectifiers

1/37

Rectifiers 1, 16 2012

Thought of the Day

Soon or late,

the man who wins

is the man

WHO THINKS HE CAN !


2/37

Diode Rectifiers

D.C. Kulshreshtha


3/37


Block Diagram ofDC Power Supply


4/37


Diodes in Rectifier Circuits


5/37


Half-wave Rectifier


6/37

Rectifiers 6, 16

2012


7/37

Rectifiers 7, 16

2012


8/37

Rectifiers 8, 16

2012

Full-wave Rectifier(Centre-tap)


9/37

Rectifiers 9, 16

2012

Full-wave Rectifier(Bridge)


10/37

Rectifiers 10, 16

2012


11/37

Rectifiers 11, 16

2012

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.


12/37

Rectifiers 12, 16

2012

PIVRatings

For half-wave rectifier : Vm


13/37

Rectifiers13

, 16

2012


14/37

Rectifiers14

, 16

2012

Figures of Merit of a Rectifier1. Ripple Factor (r) :

2. Rectification Efficiency () :


15/37

Rectifiers 15

, 16

2012

Performance of Half-wave Rectifier


16/37

Rectifiers 16

, 16

2012

Total RMS Value :


17/37

Rectifiers 17

, 16

2012

RMS Value of AC Components :


18/37


Note that this is a general result. Now, for

Half-wave Rectifier :


19/37


Performance of Full-wave Rectifier

Its period is , and not 2.How much is its period in terms oft?


20/37



21/37


Total RMS Value :


22/37


Ripple Factor :


23/37


Rectification Efficiency :


24/37



25/37



26/37



27/37



28/37



29/37


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.


30/37


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.


31/37


Filtering action depends upon the fact

that:Capacitor allows ac only to pass.

Inductor allow dc only to pass.


32/37


Shunt Capacitor Filter


33/37


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.


34/37


Discharging time constant is quite large,because it discharges through the load

resistance.

As XC


35/37



36/37


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


37/37


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.

(05) rectifiers

Documents