A PRESENTATION ON HALF WAVE RECTIFIER

H A L F W A V E

R E C T I F I E R

Simranjit Singh Shubham RanaShalini Shweta Panchal Vivek Sagar Himanshu Payal Suresh

A P R E S E N T A T I O N BY

?WHAT

A

HALF WAVE RECTIFIER

IS

.A rectifi er is an electrical device

that converts the alternating current (AC) , which periodical ly reverses direction, into the direct current (DC) , which fl ows only in one direction. This process is known as Rectifi cation.

.Physical ly, rectifi ers take a

number of forms, including vacuum tube diodes, mercury-arc valves, copper and selenium oxide rectifi ers, semiconductor diodes, si l icon-control led rectifi ers and other si l icon-based semiconductor switches .

.In half wave rectification of a single-phase

supply, either the positive or negative half of the AC wave is passed, while the other half is blocked.

.Because only one half of the input waveform

reaches the output, mean voltage is lower.

.Half-wave rectification requires a single diode in

a single-phase supply, or three in a three-phase supply. Rectifiers yield a unidirectional but pulsating direct current.

.Half-wave rectifiers produce far more ripple than

full-wave rectifiers, and much more filtering is needed to eliminate harmonics of the AC frequency from the output.

Circuit diagram

T h e h a l f - w a v e r e c t i fi e r c i r c u i t u s i n g a s e m i c o n d u c t o r d i o d e ( D ) w i t h a l o a d r e s i s t a n c e R L   . T h e d i o d e i s c o n n e c t e d i n s e r i e s w i t h t h e s e c o n d a r y o f t h e t r a n s f o r m e r a n d t h e l o a d r e s i s t a n c e R L .   T h e p r i m a r y o f t h e t r a n s f o r m e r i s b e i n g c o n n e c t e d t o t h e a c s u p p l y m a i n s .T h e a c v o l t a g e a c r o s s t h e s e c o n d a r y w i n d i n g c h a n g e s p o l a r i t i e s a f t e r e v e r y h a l f c y c l e o f i n p u t w a v e . D u r i n g t h e p o s i t i v e h a l f - c y c l e s o f t h e i n p u t a c v o l t a g e   i . e . W h e n u p p e r e n d o f t h e s e c o n d a r y w i n d i n g i s p o s i t i v e w. r. t I t s l o w e r e n d , t h e d i o d e i s f o r w a r d b i a s e d a n d t h e r e f o r e c o n d u c t s c u r r e n t . I f t h e f o r w a r d r e s i s t a n c e o f t h e d i o d e i s a s s u m e d t o b e z e r o ( i n p r a c t i c e , h o w e v e r, a s m a l l r e s i s t a n c e e x i s t s ) t h e i n p u t v o l t a g e d u r i n g t h e p o s i t i v e h a l f - c y c l e s i s d i r e c t l y a p p l i e d t o t h e l o a d r e s i s t a n c e R L , m a k i n g i t s u p p e r e n d p o s i t i v e w. r. t . I t s l o w e r e n d . T h e w a v e f o r m s o f t h e o u t p u t c u r r e n t a n d o u t p u t v o l t a g e a r e o f t h e s a m e s h a p e a s t h a t o f t h e i n p u t a c v o l t a g e .D u r i n g t h e n e g a t i v e h a l f c y c l e s o f t h e i n p u t a c v o l t a g e   i . e .   W h e n t h e l o w e r e n d o f t h e s e c o n d a r y w i n d i n g i s p o s i t i v e w. r. t . I t s u p p e r e n d , t h e d i o d e i s r e v e r s e b i a s e d a n d s o d o e s n o t c o n d u c t . T h u s d u r i n g t h e n e g a t i v e h a l f c y c l e s o f t h e i n p u t a c v o l t a g e , t h e c u r r e n t t h r o u g h a n d v o l t a g e a c r o s s t h e l o a d r e m a i n s z e r o . T h e r e v e r s e c u r r e n t , b e i n g v e r y s m a l l i n m a g n i t u d e , i s n e g l e c t e d . T h u s f o r t h e n e g a t i v e h a l f c y c l e s n o p o w e r i s d e l i v e r e d t o t h e l o a d .T h u s t h e o u t p u t v o l t a g e ( V L ) d e v e l o p e d a c r o s s l o a d r e s i s t a n c e R L     i s a s e r i e s o f p o s i t i v e h a l f c y c l e s o f a l t e r n a t i n g v o l t a g e , w i t h i n t e r v e n i n g v e r y s m a l l c o n s t a n t n e g a t i v e v o l t a g e l e v e l s . S i n c e o n l y h a l f -c y c l e s o f t h e i n p u t w a v e a r e u s e d , i t i s c a l l e d a   h a l f w a v e r e c t i fi e r.  

W o r k i n g o f a h a l f w a v e r e c t i fi e r

.TRANSFORMER.DIODE

.IC (7912).LED

.CAPACITOR.RESISTOR

Components required to make half wave rectifier :

transformer resistor

capacitor

IC (7912) diode

LED

T H A N K Y O U