Active Learning Assignment

Subject : Analog Electronics.Topic : IC voltage regulator and fixed voltage regulator. Branch : Electrical Engineering.Division : B-1

Presented By : Aniruddh Joshi(140120109001) Dheeraj Yadav(140120109010)

Chandresh Jiyani(140120109013)

Guided By : Prof. Pratik Gohel.

Gandhinagar Institute of Technology

VOLTAGE REGULATOR

A voltage regulator is designed to automatically maintain a constant voltage level. A voltage regulator may be simple “ feed forward” design or may include negative feedback control loops. It may use an electromechanical mechanism, or electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages.

IC VOLTAGE REGULATOR

IC voltage regulator means integrated circuit voltage regulator. They are basically series regulator with all the basic blocks present inside integrated circuit. IC voltage regulators are easy to use and easy to operate.

IC voltage regulators are three-terminal devices that provide a constant DC output voltage that is independent of the input voltage, output load current, and temperature.

FEATURES OF IC VOLTAGE REGULATOR

Programmable outputs.

Facility to boost the voltage/current.

Internally provided short circuit current limiting.

Thermal shut down.

Floating operation to facilitate higher voltage output.

Versatility and low cost.

CLASSIFICATION OF IC VOLTAGE REGULATOR

IC voltage regulator : Liner regulator.

: Switching regulators.

LINEAR REGULATORS

A linear regulator is a system used to maintain a steady voltage. The resistance of the regulator varies in accordance with the load resulting in a constant output voltage.

In linear regulators, a series pass transducer is used. The impedance f this transistor is continuously changed to supply the desired load current.

The series pass transistor always operates in its active region.

The linear IC regulator are either fixed voltage regulator ICs(78XX series or 79XX series) or they are variable voltage regulator ICs such as LM 317 or LM 337.

SWITCHING REGULATORS

Switching regulators are basically series type regulators with the series transistor operating as a switch.

Due to this power dissipation of the transistor is reduced and the efficiency of the regulator is increased.

This type regulator is ideal for high current applications since less power is dissipated

With switching regulators 90% efficiencies can be achieved.

Advantages of IC regulator

The power supply design becomes easy and quick.

The IC regulator are cheap and are easily available.

IC regulators are small hence they reduce the size of the power supply.

They are easy to use.

IC regulators are versatile.

They have features such as programmable output, facility to boost the Out put voltage or current, internal protection such as thermal shut down, floating operation to facilitate out put voltage etc.

Classification of three terminal IC voltage regulator

The three terminal IC voltage regulators are classified in to following categories.

Fixed voltage regulator (positive and/or negative output).

Adjustable output voltage regulator (positive and/or negative output).

The fixed voltage regulator and the adjustable voltage regulator ICs are 3-pin ICs.Therefore they are called three pin voltage regulator ICs.

Block diagram of three terminal IC voltage regulator

The block diagram is basically a series voltage regulator.

The resistor R2 & R1 from the sampling network to produce the feed back signal proportional to the output voltage.

Vref is internally generated voltage reference. This voltage reference is compared with the feed back signal by the comparator, to produce the control signal.

This control signal is routed through the thermal shut down and current limiting block to the series pass transistor.

The thermal shut down and current limiting block provides the protection increased internal temperature or over current.

If the internal temp. exceeds a predetermined value, then thermal shut down block will not allow the control signal to pass through to the series pass transistor.

This will turn off the chip automatically. The current limiting circuit protects the regulator against over current.

Three terminal fixed voltage regulator

In the fixed voltage regulator category we have positive voltage regulator and negative output voltage regulator

The μA 78XX series is a series of fixed voltage regulators and μA 79XX is the fixed negative voltage regulator.

78XX series (fixed positive voltage regulator)

78XX series are three terminal, positive fixed voltage regulator. Hence XX indicate the output voltage.

These regulators are available in seven different output voltage option, such as 5,6,8,12,15,18 and 24.

Thus if we select a regulator IC numbered ‘7812’, it provides us a 12 V regulated output voltage.

IC No. 7805 7806 7808 7812 7818 7824

O/P voltage 5V 6V 8V 12V 18V 24V

79XX series (fixed negative voltage regulator)

79XX series is also available in three pin fixed voltage category. This series or regulator Ics has designed to provide a fixed negative output voltage.

These ICs can provide -5,-6,-8,-12,-15,-18 & -24 output voltage like 78XX series.

Thus if we select a regulator IC numbered ‘7812’, it provides us a -12 V regulated output voltage.

IC No. 7905 7906 7908 7912 7918 7924

O/P voltage -5V -6V -8V -12V -18V -24V

THANK YOU