The document discusses power electronics and regulators. It covers topics such as semiconductors, doping, PN junctions, transistors, silicon controlled rectifiers, zener diodes, and regulator circuits. The key points are: - Semiconductors like silicon can be doped to create N-type or P-type materials which form the basis of diodes and transistors. - A PN junction is formed when P-type and N-type materials are joined, creating a depletion region. - Transistors involve two PN junctions and have three terminals - base, collector, emitter. Darlington transistors have very high current gain. - Zener diodes

1. Power Electronics –Regulator
Application

2. Diode and Diode Circuit
• All materials can be classified (electrically) into three categories:
» Conductors.
» Insulators.
» Semiconductors
• Conductors easily allow current to pass through them.
• Insulators do not allow current to pass through them.
Semiconductors are a group of material that posses the property of
neither insulator nor good conductor, but somewhere in between
Example of semiconductors are silicon (Si) and germanium (Ge).
• Pure semiconductors are poor conductors, because the low number of
free electrons. However, the resistivity can be reduced (so that it
conducts more current) by putting in impurities into the pure
semiconductors. The process of introducing a small amount of
impurities (during manufacturing) into the semiconductors is called
doping.

3. DOPING
•
• The type of material that is added to the pure semiconductor will determine
whether it will become n-type or p-type semiconductor.
• N-type semiconductor is produced if the impurity is either phosphorus (P),
arsenic (As), or antimony (Sb) - all from group 5 of periodic table. The
introduction of either one of these impurities into a pure
semiconductor produces more free electron in the semiconductor.
• P-type semiconductor is produced if the impurity is either aluminium (Al),
boron (B), or gallium (Ga) - all from group 3 of periodic table. The
introduction of either one of these impurities into a pure semiconductor
produces more "hole" in the semiconductor. A hole is a condition where
there is absence of one electron, which gives the effect of more positive
charge.

4. PN JUNCTION
• A p-n junction is piece of semiconductor material in which part of the material is
p-type and part is n-type. In order to examine the charge situation, assume that
separate blocks of p-type and n-type materials are pushed together. Also assume
that a hole is a positive charge carrier and that an electron is a negative charge
carrier.
• At the junction, the donated electrons in the n-type material, called majority
carriers, diffuse into the p-type material and the acceptor holes in the p-type
material diffuse into the n-type material as shown by the arrows in Figure 2.2.
• Because the n-type material has lost electrons, it acquires a positive potential with
respect to the p-type material and thus tends to prevent further movement of
electrons.
• The p-type material has gained electrons and becomes negatively charged with
respect to the n-type material and hence tends to retain holes. Thus after a short
while, the movement of electrons and holes stops due to the potential difference
across the junction, called the contact potential.
• The area in the region of the junction becomes depleted of holes and electrons due
to electron-hole recombination's, and is called a depletion layer, as shown in
Figure 2.3.

5. PN JUNCTION

6. PN JUNCTION

7. Transistors
• Transistors often involve power transfer and are usually manufactured from
silicon (resistor) material.
• The name ‘transistor’ derives from TRANSfer and resISTOR.
• The general form of a transistor is a crystal (usually silicon) in which two
pn junctions are formed.
• The junctions can be npn or pnp.
• The basic transistor has three electrode regions within the one crystal
structure (compared to two in the pn junction diode).
• These regions in a transistor are termed as base, collector, and emitter and
that there will be three connection terminals
• This form of transistor if often termed a junction transistor or bipolar
transistor.

8. Transistor

9. Transistors

10. Silicon Controlled Rectifier
• Silicon Controlled Rectifier (SCR).
• Thyristor is used for requiring high speed & high
power switching.
• Handle V & I up to 1 kV & 1000A
• Anode : high +ve voltage with relative to cathode &
gate at small +ve potential w.r.t cathode.

11. SCR

12. Transistors

13. Power electronics

16. Zener Diode
With the application of sufficient reverse voltage, a p-n junction will experience
a rapid avalanche breakdown and conduct current in the reverse direction.
Zener Regulator
The constant reverse voltage of the zener diode makes it a valuable component
for the regulation of the output voltage. The current through the zener will change
to keep the voltage at within the limits of the threshold current and the
maximum power it can dissipate

17. Is
Vo  Vz
Vs  IsRs  Vo
Vs  Vo
Is 
Rs
Vo
IL 
RL
KCL : Is  Iz  Io
Iz  Is  Io
(Any components in parallel with Zener, it will follow Vz)

18. Proton Saga 1.3L
Shunt Regulator – Overflow currents shunt away from Zener diode

19. Is
Vo  VCE  Vz  VBE
Ic IL Vs  IsRs  Vz  VBE  IsRs  Vo
Vs  Vo
Is 
Rs
Vo
IL 
RL
Is  Iz  Ic  I L
Basic Idea: IZ = IB Ic  Is  I L , as Iz small compare to Ic
Vs = VRS + Vo IC = βIB
Proton Saga 1.5L
When Vo↑, VBE ↑, IB ↑, IC ↑, IL↓, Vo normal

22. Iswara
VB  VZ  VBE  VO
Vo ↑, VBE↓, IB↓, VO  VZ  VBE , VZ constant
(IC=IL)↓, Vo normal
VO
VB IL 
Vo ↓, VBE ↑, IB↑, RL
(IC=IL)↑, Vo normal PD  I CVCE  I L (VS  VO ) in which I C  I L

23. LINE REGULALTION

25. LOAD REGULATION
= IE
(IR = IZ + IB)

26. (OPEN)
(SHORT)

27. IR
•In normal operation, VB = VZ
•The current flowing through resistor R is:
VB  VZ  VBE  VO
VS  VR  VZ
VS  VZ
VR  VS  VZ , I R R  VS  VZ , I R 
R
IR  IB  IZ
•For a fixed Vs (and also Vz), IR is a fixed value
•When IB increases, Iz will decrease
•In order to get a good regulation, Iz must be larger than
a minimum value IZK over the rated range of load current

32. Darlington Transistors
Darlington transistor combines two bipolar transistors in “Darlington pair")
in a single device so that the current amplified by the first is amplified further
by the second transistor.
This gives it high current gain and takes up less space than using two discrete
transistors in the same configuration.
I C1  I B 2  β1 I B1
I C 2  β2 I B 2  β2 β1 I B1
A typical modern device has a current gain of 1000 or more, so that only a tiny
base current is required to make the pair switch on.
Example:
Typical Darlington transistor has current gain of 1000.
If input current is 10mA, means that output current, IC = 10mA x 1000 = 10A

34. Conclusion:
Darlington transistor required less base current, IB to produced the required
amount of IL. So less Iz drawn away from zener diode and the stability
of the circuit can be maintained.

39. WIRA

41. Concept: Depends on the voltage different between V+ and V-
When Vo↑, VR2 ↑, (V+ -V-)↓, IB↓, (IC=IL)↓, Vo normal

45. VR2 = VBE2 + VZ (constant)IR3 = IC2 + IB1
Concept: Depends on the VBE2
When Vo↑, VR2 ↑, VBE2↑, IC2↑, IB1↓, IC1↓, Vo normal

52. New equivalent circuit when the output is accidentally shorted
18v Analysis: Condition under short circuit
Vo = 0V, no feedback voltage, VBE = 0V
200Ω
Q2 off.
Now:
VS  VBE 18  0.7
I R3    86.5mA
R3 200
SINCE ,
POWER DISSIPATION I R 3  I B1
PD  VCE1  I C1 So,
I C1  I B1  100  86.5mA  8.65 A
PD  (VS  0)  I C1
PD  18V  8.65 A
PD  155.7W

53. P4 with 75Watts Power dissipation

55. 1A

57. Protection Network

58. Protection network off
Protection network on
Current through Q1 Current overflow
Through Diodes

64. VBE < 0.7V

65. Equivalent Circuit Under Short Circuit Condition
Transistor turns ON before output load short circuit:
Concept: More short; more current shunt away
Under Short Circuit Condition:
Most of the output voltage now dropped across RCS. VRB becomes
Large and shunt away most of the current from IR3.
RB
VBE  ( )VRCS
RA  RB

82. Heat Sink