SHAHAJIRAO PATIL VIKAS PRATISHTHANS. B. PATIL COLLEGE OF ENGINEERING, INDAPUR, DIST: PUNE. DEPARTMENT OF ELECTRICAL ENGINEERING

Experiment No: Study of voltage regulation of IC 7812, 7912 and LM317.

1.0 AIM:

Study of voltage regulation of IC 7812, 7912 and LM317.

APPARATUS:

Voltage regulator IC 7812, 7912 & LM317 kit.

C.R.O.

Digital multi meter.

3.0 THEORY:

3.1 VOLTAGE REGULATORS:

Figure shows the basic connection of a three-terminal voltage regulator IC to a load. The fixed voltage regulator has an unregulated dc input voltage Vin applied to one input terminal, a regulated output dc voltage V0 from a second terminal, with third terminal connected to ground. For a selected regulator, IC device specifications lists a voltage range over which the input voltage can vary to maintain a regulated output voltage over a range of load current. The specifications also list the amount voltage change resulting from a change in load current (load regulation) or input voltage (line regulation).

3.2 FIXED POSITIVE VOLTAGE REGULATOR:

The series 78 regulators provide fixed regulated voltages from 5 to 24 V. An IC 7812 is connected to provide voltage regulation with output from this unit of +12V dc. An unregulated input voltage Vin is filtered by capacitor connected to the ICs IN terminal. ICs OUT terminal provides a regulated +12V, which is filtered by capacitor at the out terminal (mostly for any high frequency noise).The third IC terminal is connected to ground (GND).

The ac line voltage (230 VRMS) is stepped down to 18 VRMS across each half of the center-tapped transformer. A full-wave rectifier and capacitor filter then provides an unregulated dc voltage, shown as a dc voltage of about 22V. with ac ripple of a few volts as input to the voltage regulator. The 7812 IC then provides an output that is a regulated +12V dc.

3.3 FIXED NEGATIVE VOLTAGE REGULATORS:

The series 79xx ICs provide negative voltage regulation, similar to those providing positive voltage regulations.

3.4 ADJUSTABLE VOLTAGE REGULATOR:

The regulators are also available in circuits that allow the user to get the output voltage to desired regulated value. LM317 can be with the output voltage regulated at any setting over the range of voltage 1.2V to 37V. Resistor R1 & R2 set the output to any desired voltage over adjustable range.

4.0 CIRCUIT DIAGRAM:

Draw neat circuit diagram and pin diagram of all 7812, 7912 and LM317 voltage

regulator ICs.

PROCEDURE:

Do connections as shown in the circuit diagram.

Make power on to the unit.

For various input voltages verify output of IC regulator. Take down readings in observation table1.

For various load resistances verify output of IC regulator. Take down readings in observation table2.

6.0 OBSERVATION TABLE 1 (LINE REGULATION):

To verify that output voltage remains constant, irrespective of the changes In the input supply voltage.

SR.NO.

Input ac voltageOutput voltage of the

(Vin)regulator (Vo)

1

2

3

4

7.0 OBSERVATION TABLE 2 (LOAD REGULATION):

To verify that output voltage remains constant, irrespective of the changes in the load.

SR.NO.LOAD RESISTANCELOADOUTPUT

CURRENTVOLTAGE OF

(IL) IN mATHE

REGULATOR(V0)

1RL1

2RL1 + RL2

3RL1 +RL2 +RL3

4RL1 +RL2+ RL3+ RL4

8.0 CONCLUSION:

QUESTIONS RELATED TO EXPERIMENT:

What is voltage regulation? Why is it necessary?

State and explain any four parameters of voltage regulation?