BY

PROF VISHNU NARAYAN SAXENA

RECTIFIER

RECTIFIER IS A DEVICE THAT CAN CONVERT AC IN TO DC

SO THERE ARE TWO QUESTIONS

WHY WE NEED TO CONVERT A.C. IN TO D.C.

AND WHAT IS A.C. AND WHAT IS D.C.

ALTERNATING CURRENT IS THAT CURRENT WHICH DIRECTION REVERSE PERIODICALLY

AND

IN DIRECT CURRENT IS THAT CURRENT IN WHICH THE DIRECTION OF CURRENT REMAIN SAME

1.Step Down Transformer

The function of step down transformer is to convert high A.C. Voltage(230 V) to Low A.C. Voltage (15V,12V etc)Because we can't apply high ac voltage to diode directly

2. Semiconductor Diode

Building Blocks of Rectifier

Diode is a semiconductor switching device Which has two terminal

1. Anode

2. Cathode

Diode can be conncted in any circuit either in forward bias or reverse bias

FORWARD BIAS: When anode is connected with +ve terminal of battery and cathode is connected with –ve terminal of Battery Diode is in forward bias and its resistance drop down to 0(r = 0) and it behaves like a close switch

REVERSE BIAS: When anode is connected with -ve terminal of battery and cathode is connected with +ve terminal of Battery Diode is in reverse bias and its resistance rises up to infiniteand it behaves like an open switch

AC Voltage is first stepped down then applied to the diode

During +ve Half Cycle Point A Will be at positive potential whereas point B will be at –ve Potential

Diode D Will be in Forward Bias and behave like a close switch

And positive half cycle will be passed as it is As Shown in fig

During Negative Half Cycle Point A will be At Negative Potential As Compared to Point B So Diode is in Reverse Bias and Behaves Like an Open Switch and negative half cycle does not passes to the load resistance

NOW WORKING OF RECTIFIER

DURING POSITIVE HALF CYCLE DIODE IS IN FORWARD BIAS AND BEHAVES LIKE A CLOSED SWITCH AND POSITIVE HALF CYCLE PASSES TO THE LOAD RESISTANCE

DURING NEGATIVE HALF CYCLE DIODE IS IN REVERSE BIAS AND BEHAVES LIKE AN OPEN SWITCH AND NEGATIVE HALF CYCLE DOES NOT PASSES TO THE LOAD RESISTANCE

IN THIS WAY HALF WAVE RECTIFIER CONVERT HALF CYCLE OF AN A.C. VOLTAGE TO THE D.C. VOLTAGE