Learn the fundamentals of DC power supplies. How they work and learn the basics of HWR, FWR and BR using simple concepts. This slideshow is based on the textbook 'APPLIED ELECTRONICS' written by Vidyasagar Sir. For more details about this book, visit: http://www.yashplus.com/portfolio/vocational-electronics-publications/

1. Rectifiers (HWR, FWR & BR)
Filter Circuits (Series & Shunt)
Regulators (Zener & Transistor)
3-Terminal Voltage Regulators
Switch Mode Power Supply

3. Vp

Rectifier Circuits (HWR)
It is a low quality rectifier circuit.
It rectifies only one half cycle of AC.
Its output voltage is equal to Vp/.
The PIV of the diode is greater than Vp.
Its ripple frequency is equal to
frequency of AC voltage.
The current through the diode is equal
to load current.
27.02.2009
Designed by:
D.S.Vidyasagar

5. Rectifier Circuits (FWR)
It is a good quality rectifier circuit.
It rectifies both half cycles of AC.
Its output voltage is equal to 2Vp/.
The PIV of diode is greater than 2Vp.
Its ripple frequency is double than the
frequency of AC voltage.
The current through each diode is half
of the total load current.
27.02.2009
Designed by:
D.S.Vidyasagar

7. Rectifier Circuits (BR)
It is a best quality rectifier circuit.
It rectifies both half cycles of AC.
Its output voltage is equal to 2Vp/.
The PIV of the diode is greater than Vp.
Its ripple frequency is double than the
frequency of AC voltage.
The current through each diode is equal
to the total load current.
27.02.2009
Designed by:
D.S.Vidyasagar

8. Filter Circuits (Basics)
The ripple means variations in impure DC
voltage.
Due to ripples the quality of DC voltage is
reduced.
Thus, the ripple factor is defined as the
ratio of r.m.s. value of AC voltage to DC
voltage.
The ripple factor is independent of RL.
27.02.2009
Designed by:
D.S.Vidyasagar

9. Filter Circuits (Basics-2)
The inductor can also store electricity in
The capacitor can store electricity in the
form of of across it.
the form PDPD across it, for a short time.
InIn capacitor currentlags voltage by 90.
inductor current leads voltage by 90 .
It charges upallows DCand discharges up
to 63.28% current and
The inductor
to 36.72% in time T=RxC.
produces high opposition (XL) to AC.
It allows AC current with opposition (Xc)
Thus,blocks DC.steady current but
but it allows
opposes changing current.
27.02.2009
Designed by:
D.S.Vidyasagar

11. Capacitor Filter Circuit
When filter circuit is used load must be
connected across the output.
When first half cycle arrives, the capacitor
charges up to Vp.
When rectifier voltage drops, it gives out
its stored energy to the load.
Thus, it maintains constant voltage.
Its filtration decreases as RL decreases.
27.02.2009
Designed by:
D.S.Vidyasagar

13. Inductor Filter Circuit
When filter circuit is used load must be
connected across the output.
When first half cycle arrives, the current
through inductor increases.
When voltage of first half cycle drops
counter current opposes this change.
Thus, inductor produces opposition to
changing current and allows pure DC only.
Its filtration increases as RL decreases.
27.02.2009
Designed by:
D.S.Vidyasagar

15. Voltage Regulators
A load means anything which we connect
across the output of a circuit.
When load is connected, loading effect is
produced.
Due to loading effect, the output voltage
drops.
This loaded voltage is called apparent
voltage.
The apparent voltage is always less than
true voltage.
27.02.2009
Designed by:
D.S.Vidyasagar

16. Voltage Regulators
Load regulation is defined as the
change in output voltage when load
current changes from minimum to
maximum.
Line regulation is defined as change
in output voltage for a specified range
of line voltage.
27.02.2009
Designed by:
D.S.Vidyasagar

17. Voltage Regulators
Voltage regulator has two important
facilities –
It has over voltage protection i.e.
when line voltage is abnormal it is
switched off.
It has over load protection i.e. when
load current exceeds the limit, it is
switched off.
27.02.2009
Designed by:
D.S.Vidyasagar

18. Zener Regulators
The zener diode is a special PN junction
diode.
Its doping concentration decides the zener
voltage.
When a  +ve, k  –ve, its forward
voltage is 0.7V.
It cannot be used in rectification, since it
conducts in both directions.
When load resistor is disconnected from
the circuit, total current flows through it.
27.02.2009
Designed by:
D.S.Vidyasagar

19. Shunt Zener Regulator
The circuit stabilizes the output voltage,
when RL = constant, as follows –
When Vin  Is  Iz  but IL= constant
So (Vin – Vz) and Vz = Vo = constant
When Vin  Is  Iz  but IL= constant
So (Vin – Vz)  and Vz = Vo = constant
27.02.2009
Designed by:
D.S.Vidyasagar

20. IS = IZ + IL
constant

21. IS = IZ + IL
constant

22. Shunt Zener Regulator
The circuit stabilizes the output voltage
when Vin = constant, as follows –
When RL IL but Is = constant
So Iz  and keeps Vo = constant
When RL IL  but Is = constant
So Iz  and keeps Vo = constant
27.02.2009
Designed by:
D.S.Vidyasagar

23. constant
IS = IZ + IL
constant

24. constant
IS = IZ + IL
constant

25. +ve
+ve
In any other
Forward biased
condition it is
reversed biased
–ve

26. Ic
Ie = Ic + Ib
Ib
Ic =  x Ib
Ie

27. Ic
Ie = Ic + Ib
Ib
Ic =  x Ib
Ie

28. Ie = Ic + Ib
Ib
Ic =  x Ib

29. Vb
Vc

30. Vb
Vc

31. constant

32. constant

33. 0.6V
FB
Vo = 0

34. Pin-1 unregulated input
Pin-2 regulated output
Pin-3 ground pin

35. Vo = Vin – Vce
constant

36. Vo = Vin – Vce
constant

37. 175

39. LM 340–12
15V
12V

40. 15V
12V
LM 340–05

41. Switch Mode Power Supply
It is a sophisticated power supply.
It produces very pure DC voltage.
It has a square wave generator
circuit.
Its operating frequency is 20kHz.
During +ve half cycle of square wave,
the transistor conducts.
During –ve half cycle, it is cut-off.
27.02.2009
Designed by:
D.S.Vidyasagar

42. Switch Mode Power Supply
Its operating frequency is very high,
generally 20kHz.
So the valleys at output have small
width.
This width can be easily filled up
using small filter capacitor.
Its output voltage Vo = D x Vin
27.02.2009
Designed by:
D.S.Vidyasagar

43. Advantages of SMPS
The transistor dissipates very little
power in it.
So output is proportional to input.
It has high efficiency output.
It has high current output.
Hence, loading effects are negligible.
Due to high frequency, ripples are less.
27.02.2009
Designed by:
D.S.Vidyasagar

44. 22.12.2013
Designed by:
Prof. D.S.Vidyasagar