Voltage regulators

IC REGULATORS

1. V ol t a g e R egul a t o r s

2. Co n t e n ts • I n t r oduction Series o p- amp r egul at or IC v ol t a g e r egul a t o r s 723 g ene r al purpose r egul a t or S wi t ching r egul a t or • • • •

3. I n t r oduction • The funct i on of v ol t a g e r egul a t or is t o p r o v i d e a c on s t a n t s t able dc v ol t a g e f or po w er i ng other elect r onic ci r cuits. • V ol t a g e r egul a t o r s a r e c l assif i ed as: 1. 2. Ser i es or linear r egul at or S wi t ch i ng r egu l a t or

4. Series or Linear r egul a t or • T h e y use a p o w er t r ansi s t or c onne c t ed in ser i es b e t w een the un r egul a t ed dc i n put and load.

5. • T he o utput v ol t a g e i s c o n t r ol l ed b y the c o n ti n uous v ol t a g e d r op t a k i n g p l a c e a c r oss the ser i es pass t r ansi s t o r . As t r ansi s t o r s w or k s in the a cti v e o r l i near r egion, these r egul a t o r s also k n o wn as l i near r egul a t o r s. • a r e Series or Linear r egul a t or

6. • • Series or Linear r egul a t or Advantages Disadvantages Simple circuit configuration Few external parts Low noise Relatively poor efficiency Considerable heat generation Only step-down (buck) operation

7. S wi t ching r egul a t o r s • A switching regulator is a voltage regulator that uses a switching element to transform the incoming power supply into a pulsed voltage, which is then smoothed using capacitors, inductors, and other elements. Power is supplied from the input to the output by turning ON a switch (MOSFET) until the desired voltage is reached. Once the output voltage reaches the predetermined value the switch element is turned OFF and no input power is consumed. Repeating this operation at high speeds makes it possible to supply voltage efficiently and with less heat generation. • This gi v es im p r o v ed e f f i ciency o v er ser i es r egul a t o r .

8. S wi t ching r egul a t o r s Advantages Disadvantages High efficiency Low heat generation Boost/buck/negative voltage operation possible More external parts required Complicated design Increased noise

9. Series op - amp r egul a t or • A v ol t a g e r egul a t or is a elect r onic ci r cuit th a t p r o v i d es a s t able dc v ol t a g e i ndepende n t of lo a d, t empe r a tu r e and ac l i n e v ol t a g e v ari a tions.

10. • T he c i r cuit c onsi s ts of f our ma j or c omp o ne n ts. 1. 2. 3. 4. R e f e r ence v ol t a g e ci r cuit ( Z ener diode) Er r or amplifier (Di f f e r e n ce ampli f ier) Series pass t r ansi s t or (Q1) F e e db a ck n e t w ork (R1 and R2)

11. • T he t r ansi s t or Q1 is c onne c t ed as an emi t t er f ol l o w er a nd the r e f o r e p r o v i d e su f fic i e n t cur r e n t g ain t o dr i v e the lo a d. • T he o utput v ol t a g e i s sampled b y po t e n tial d i v i de r s R1 and R2 ( f eedback n e t w ork) a nd f eedback t o the i n v ert i ng i n put t erm i nal of the o p- amp er r or ampl i fie r . • If t he output v ol t a g e i nc r eases s a y due t o v ari a t i on in load cur r e n t the sampled v ol t a g e β V also i n c r eases. Wh i ch in turn r educes the outp u t v ol t a g e of the d i f f e r ence ampli f ier due t o the 180⁰ phase sh i ft p r o v i d ed b y the o p - amp amp l i f i e r .

12. IC V ol t a g e R egul a t or The r e a r e t w o c a t e g or i es 1. 78XX / 79XX Fi x ed V ol t a g e Series r egul at o r s 2. 723 g ene r al p u r p ose r egu l a t o r s

13. Fi x ed V ol t a g e Series R egul a t or • 78XX ser i es a r e th r ee t erm i nal pos i t i v e f i x ed v ol t a g e r egul a t o r s. • In 78 X X, the la s t t w o numbe r s ‘X X ’ i n d i c a t e the output v ol t a g e. • Eg : 7805 7808 +5V +8V • 79XX ser i es a r e th r ee t erm i nal, ne g a ti v e f i x ed v ol t a g e r egul a t o r s.

14. • Capa c i t o r s a r e c onnec t ed b e t w een input t erminal and g r ound t o c ancel the induc t i v e ef f ect due t o l o ng di s tr i bution leads. Ou t put c apaci t ance imp r o v es the t r ansie n t r esponse.

15. Cha r ac t eri s tics of IC V ol t a g e R egul a t o r s 1.  2.  3.  4. R e g ul a t ed out p ut v o l t a g e( V ) 7 8 XX has output v ol t a g e 5, 6 , 8 e t c. Un r eg u l a t ed input v ol t a g e(Vi n ) i.e If V =5 V t hen Vin=7 V | 𝑉 𝑖 | ≥ | 𝑉 | + 2𝑉 M a ximum output cu r r e n t( I 0m a x ) M a y v a r y f r om t o m a ximum r a t ed cur r e n t Thermal shu t down  H a s senso r s which turn s - o f f the IC when it be c omes c e lciou s ) t oo h o t (1 2 5 t o 1 5 0 deg

16. Limi t a tions • No short ci r cuit p r o t ection • Output v ol t a g e i s fi x ed

17. Impor t a n t per f ormance pa r am e t e r s

18. Impor t a n t per f ormance pa r am e t e r s

19. IC r egul a t or us e d as cur r e n t s o u r ce

20. Cur r e n t boo s t er ci r cuit

21. Impor t a n t f ormulas:

22. Fi x ed r egul a t or used as adju s t able r egul a t or

23. 723 Gene r al P urpose R egul a t or

24. 723 Gene r al P urpose R egul a t or

25. IC 723 PIN Diag r am

26. IC 723 as l o w v ol t a g e r egul a t or ( V o= 2V t o 7V)

27. IC 723 as high v ol t a g e r egul a t or ( V o>7V)

28. S wi t ching R egul a t or