Electronic PRINCIPLES

Transcription

1 MALVINO & BATES Electronic PRINCIPLES SEVENTH EDITION Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

2 Chapter 24 Regulated Power Supplies Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

3 Topics Covered in Chapter 24 Supply characteristics Shunt regulators Series regulators Monolithic linear regulators Current boosters DC-to-dc converters Switching regulators Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

4 Supply characteristics Load regulation how much the output voltage changes when load current changes Line regulation how much the load voltage changes when the line voltage changes Output resistance determines the load regulation Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

5 Power supply regulation V line V out V Load regulation = NL - V FL x 100% V FL V Line regulation = HL - V LL x 100% V LL Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

6 Shunt regulator The zener regulator is the simplest example of a shunt regulator Adding transistors and op amps will improve line and load regulation The main disadvantage is low efficiency Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

7 Zener diode shunt voltage regulator R S Power supply V in V Z V out V out = V Z I S = V in - V out R S I L = V out I Z = I S - I L Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

8 Improved shunt voltage regulator R S Power supply V in V Z V out V out = V Z + V BE I S = V in - V out R S I L = V out I C I S - I L Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

9 Series regulator Uses a pass transistor instead of a series resistor Has a higher efficiency than a shunt regulator A zener follower is the simplest series regulator Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

10 Zener follower is a series voltage regulator Power supply V in R S P D (V in - V out )I L V out = V Z V BE V Z V out Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

11 Two-transistor voltage regulator +V in R 1 R 2 V out = R 3 + R 4 R 4 (V Z + V BE ) Q 2 R 3 V Z Q 1 R 4 V out Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

12 Improved voltage regulator +V in V out = R 2 + R 3 R 3 V Z R 1 R 2 V Z R 3 V out Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

13 Regulator with current limiting Q 1 V out = R 2 + R 3 R 3 V Z +V in R 4 R 1 R 2 R 5 Q 2 V out I SL = V BE R 4 R 3 V Z Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

14 V L Simple current-limiting V reg V BE(Q2) 06 V Constant current region I SL I L Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

15 Foldback current limiting R 1 Q 1 K = +V in R 4 R 7 R 6 +R 7 R 6 R 7 I SL = V BE KR 4 R 2 R 5 Q 2 R 3 V Z I max = I SL + (1-K)V out KR 4 Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

16 V L Foldback current-limiting V reg Foldback current region I SL I max I L Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

17 Monolithic linear regulators IC regulators can be: Fixed positive Fixed negative Adjustable Classified as: Standard Low power Low dropout Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

18 Monolithic regulator with current booster V in Q 1 R LM78XX 3 V out Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

19 Current booster An outboard transistor is used to increase the regulated load current Short-circuit protection is provided by adding another transistor Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

20 Current booster with current limiting V in R 2 Q 2 Q LM78XX V out R 1 3 Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

21 Dc-to dc converter Used to convert an input dc voltage to an output dc voltage of another value Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

22 DC-to-DC converter circuit +V in R 1 Q 2 T 1 v in Q 1 Q 3 R 2 Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

23 Switching regulators The pass transistor is switched between cutoff and saturation Better efficiency than linear Topologies: Buck: steps the voltage down Boost: steps the voltage up Buck-boost: inverts the input voltage Popular in computer and portable electronic systems Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

24 Buck regulator Q +V in D L C R 2 PWM V out = DV in V REF R 1 Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

25 Boost regulator +V in L V kick V p Q D C R 2 PWM V p = V in + V kick V REF R 1 Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

26 Buck-boost regulator Q +V in L D C R 2 PWM V REF R 1 Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

27 Monolithic buck regulator +V in 5 4 IN OUT L C 1 LT1074 D C 3 R 2 R 3 C 2 COMP 2 FB 3 1 V out = R 1 + R 2 R 1 (221 V) R 1 Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display

28 Using the charge pump of the MAX633 IC +V in 4 IN OUT CP MAX C V C 3-12 V 1,3,7 D 1 D 2 C 2 Copyright The McGraw-Hill Companies, Inc Permission required for reproduction or display