Published on October 13, 2014
1. A Presentation on IC VOLTAGE REGULATORS submitted in partial fulfillment for the award of the degree of Bachelor Of Technology (Rajasthan Technical University, Kota) Submitted by:- Gajendra Singh 8th sem ECE Submitted to:- Sanjay Kumar Singhal Head Of Department
2. INTRODUCTION Voltage regulator :- It is a circuit that supplies constant voltage regardless of changes in the load current.
3. Need for regulation Without stable potentials, circuit performance degrades and if the variations are large enough the components may get destroyed. In order to avoid this problem regulation is used.
4. Basic power supply Transformer: Steps down high voltage AC mains to low voltage AC. Rectifier:converts AC to DC, but the DC output is varying. Filter: smooth the DC from varying greatly to a small ripple. Regulator : Eliminates ripple by setting DC output to a fixed voltage.
5. IC Voltage Regulators Advantages of IC voltage regulator Inexpensive Versatile Provides current /voltage boosting Internal short circuit current limiting
6. Classification of IC voltage regulators: There are basically two kinds of IC voltage regulators: Multi-pin type, e.g. LM723C 3-pin type, e.g. 78/79XX Multi-pin regulators are less popular but they provide the greatest flexibility and produce the highest quality voltage regulation. 3-pin types make regulator circuit design simple
7. Types of IC voltage regulators: 1. Fixed output voltage regulators: Positive fixed output regulator(78XX series) and negative fixed output regulator(79XX series). 2. Adjustable output voltage regulators: Positive (LM317) and negative(LM337). 3. Switching regulators: Motorola ‘s MC1723. NOTE: MC1723 is a general purpose regulator ;it can be used in many ways as a fixed positive or negative output voltage regulator, variable output voltage regulator or as a switching regulator. Due to its flexibility it has become as a standard type in the electronics industry.
8. Topics to be dealt • 78XX series • 79XX series • 317 variable regulators • 1723 switching regulators
9. Performance parameters of voltage regulators Line or input regulation: Defined as a change in output voltage for a change in input voltage. Load regulation: Defined as the change in output voltage for a change in load current. Temperature stability or average temperature coefficient of output voltage(TCVO): Defined as the change in output voltage per unit change in temperature and expressed in millivolts per degree Celsius. Ripple rejection: It is the measure of regulator’s ability to reject ripple voltages. It is usually expressed in decibels. The smaller the value of these performance parameters ,the better the regulator.
10. FIXED VOLTAGE REGULATOR a)Positive voltage regulator • The 78XX voltage regulators • Fig shows the connection diagram of 78XX series • Proper operation requires a common ground between the input and output voltages.
11. 78XX basic features IC No Voltage 7805 5V 7806 6V 7808 8V 7809 9V 7810 10V 7812 12V 7815 15V 7818 18V 7824 24V • Features • 3 terminal positive voltage regulator with nine voltage options • High Output Current - typically 1.5A • Short circuit current limit - 750mA at 5v • Max input voltage = 35v • Minimum Input Voltage = Vout + 2.5
12. 7805 as current source The 7805 regulators can also be employed as current sources. A typical connection diagram of 7805 IC as a 0.5 A current source is depicted in figure.
13. b)Negative voltage regulators • Negative voltage regulator IC's are available in 79XX series. • These IC's are similar to the 78 series, but operating on negative voltage, and providing a regulated negative output voltage. • The capacitors connected at the input and output sides are used to provide additional filter circuits of regulator circuits.
14. Features of 79XX IC No Voltage 7902 -2V 7905 -5V 7905.5 -5.2V 7906 -6.2V 7908 -8V 7912 -12V 7915 -15V 7918 -18V 7924 -24V • Same as that of 78XX series except that 79XX series are negative regulators • They are available in same seven voltage options with two extra voltage options,-2V and - 5.2V.
15. ADJUSTABLE VOLTAGE REGULATOR Adjustable voltage regulators are those who voltage can be varied and utilized. Advantages of adjustable voltage regulators Improved system performance Improved overload protection Improved system reliability Example: LM317
16. 1) Positive Adjustable Voltage Regulators- LM317 • The LM317 is a three terminal positive voltage regulator, which can be operated with the output voltage regulated at any setting over the range of 1.2 V to 57 V. • The three terminals are Vin. Vout and Adjustment(adj).
17. 2) Negative Adjustable Voltage Regulators- LM337 • The LM337 series of voltage regulators are a complement of LM317 series. • They are negative adjustable voltage regulators • These negative voltage regulators are available in the same voltage and current options as the positive adjustable voltage regulator LM317.
18. Switching Regulator • In switching regulator, the transistor acts as a switch. • When the transistor is off(switch is open), no current flows, therefore no power dissipation. • When the transistor is on,(switch is closed), high current flows but Vce becomes low and therefore power dissipation is less.
19. Features MC1723 • Delivers load current of about 150mA without an external pass transistor. • Output voltage range 3Vdc to 37 Vdc. • It is a general purpose regulator and can be used as fixed variable and switching regulator. • The regulator requires an external transistor and a 1mh choke. • To minimize its power dissipation during switching, external transistor used must be switching power transistor.
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