REGULATORS AND POWER SUPPLY
Functions of each block:
1)Transformer:ItConverts an AC input source toAC required outputwithout changing frequency. The
transformer is step up or step down transformer.
2)Rectifier:It is a circuit which is usedto convertAC into pulsating DC. A rectifying diode is used.
3) Filter:It is a circuit usedto convert pulsatingDC into pure DC. A inductor and capacitors are usedas
filter
4)Voltage regulator:Anunregulated DC voltage isconverted into regulatedDC voltage. IC 78XX &
79XX series are used as regulator.
ZENER DIODE AS A VOLTAGE REGULATOR
DIAGRAMof zener diode as voltage regulator:
, WORKING :
I. Zener Diodes arewidely used as Shunt Voltage Regulatorsto regulate voltageacross small loads.
II. Zener Diodeshave a sharp reverse breakdown voltageandbreakdown voltage will be constant for
a wide range of currents.
III. Thus we will connect the zener diode parallel to the loadsuch that the applied voltage will reverse
bias it.
IV. Thusif the reverse bias voltage across the zenerdiode exceeds the knee voltage, the voltage across
the load will be constant.
VOLTAGE REGULATOR
NEED
● Thepurposeof a voltage regulatoris to keep thevoltage in a circuit relatively close to a desired
value.
● There areconsiderable variations in a.c. line voltagecaused by outside factors.This changes the
d.c. output voltage and may damage the electronic circuitsand appliances. This necessitates to use
regulator.
● Theinternal resistance of ordinary power supplyisrelativelylarge(>3Ω). Therefore, output
voltage is affected by the amount of load currentdrawn from the supply.
● These variation in d.c. voltage may cause deviation in operation of electronic circuits.Therefore,
voltage regulator is the only solution in such situations.
Functions of each block:
1)Transformer:ItConverts an AC input source toAC required outputwithout changing frequency. The
transformer is step up or step down transformer.
2)Rectifier:It is a circuit which is usedto convertAC into pulsating DC. A rectifying diode is used.
3) Filter:It is a circuit usedto convert pulsatingDC into pure DC. A inductor and capacitors are usedas
filter
4)Voltage regulator:Anunregulated DC voltage isconverted into regulatedDC voltage. IC 78XX &
79XX series are used as regulator.
ZENER DIODE AS A VOLTAGE REGULATOR
DIAGRAMof zener diode as voltage regulator:
, WORKING :
I. Zener Diodes arewidely used as Shunt Voltage Regulatorsto regulate voltageacross small loads.
II. Zener Diodeshave a sharp reverse breakdown voltageandbreakdown voltage will be constant for
a wide range of currents.
III. Thus we will connect the zener diode parallel to the loadsuch that the applied voltage will reverse
bias it.
IV. Thusif the reverse bias voltage across the zenerdiode exceeds the knee voltage, the voltage across
the load will be constant.
VOLTAGE REGULATOR
NEED
● Thepurposeof a voltage regulatoris to keep thevoltage in a circuit relatively close to a desired
value.
● There areconsiderable variations in a.c. line voltagecaused by outside factors.This changes the
d.c. output voltage and may damage the electronic circuitsand appliances. This necessitates to use
regulator.
● Theinternal resistance of ordinary power supplyisrelativelylarge(>3Ω). Therefore, output
voltage is affected by the amount of load currentdrawn from the supply.
● These variation in d.c. voltage may cause deviation in operation of electronic circuits.Therefore,
voltage regulator is the only solution in such situations.
