1. UEENEEG008B
Part A
Electronic power and control 1

2. Textbooks
Electrical Trade Principles
Jeffery Hampson and Steven Hanssen
Revision 01 2

3. This is an introductory module only and it leads
onto other electronic and power control studies
 Principle of operation of common semi-conductor
devices
 Single and 3 phase rectifiers, (½ and full wave)
 Filters and Voltage Regulators
 Operating principles, and safety of inverters
 Principles and operation of common transducers
 Principles and operation of programmable relays
Revision 01 3

4. Semiconductors
• Silicon is bonded or doped with another
element
• When the silicon has one less electron in the
bond it is called a P Type material
• When the silicon has more electron in the
bond it is called a N Type material
Revision 01 4

5. Rectifier Diodes
• The P-N Junction
• Diodes….
• In simple terms, diodes allow current to flow
in 1 direction only.
Revision 01 5

6. The p-n Junction
When p-type material and n-type material are
fused together, a p-n junction is formed.
Some free electrons move across the
junction to occupy some of the holes and an
area depleted of current carriers is created.
p-type n-type
-- +
+
-- +
+
-- +
+
Depletion
Layer
Revision 01 6

7. Barrier potential
p-type n-type
-- +
+
-- +
+
-- +
+
Barrier Potential
 Electrons move from the n type material to the p type material
and fill available holes.
 The loss of electrons from the n-type material results in a +ve
charge
 The gained electrons in the p-type material results in a -ve
charge
 These charged areas form the BARRIER POTENTIAL
 These charges form a BARRIER POTENTIAL of about 0.7 volts
for Silicon and 0.3 volts for Germanium
7

8. Forward bias
P type N type
- -- +
+ +
- - + +
- -- +
+ +
holes electrons
 +ve potential connected to p-type –ve potential connected to
n-type
 At the same time, electrons flow from the (-ve) terminal of the
supply through the n-type material into the depletion region.
 The effect is the cancelling of the barrier potential.
 Therefore, the p-n junction will conduct in this direction.
 Current will flow in the direction shown.
 Electrons are attracted from the depletion region, and flow
through the p-type material to the (+ve) terminal of the
supply.
Revision 01 8

9. Reverse bias
P type N type
- -- + +
+
- -- +
+ +
- -- +
+ +
electrons electrons
• + ve potential connected to n-type – ve potential connected to p-
type
• A few electrons moving from the (-) terminal flowing through the
p type material. A few electrons will also flow from the n-type
material to the (+) terminal.
• The effect is a large increase in the barrier potential.
• Therefore, the diode WILL NOT CONDUCT in this direction.
Revision 01 9

10. Diode characteristic curves
IF
Reverse Bias mA Silicon
Diode
200V 100 0
V
0.6 1.0 V
VR
Breakdown IR Forward Voltage VF
Voltage VBR
Germaniu
m Diode µA
Diode US Forward Bias
Revision 01 10

11. Diode specifications
• Forward Voltage VF -The value of the voltage drop across a
forward bias diode.
• Average Forward Current IF - The average current of a forward
bias diode.
• IF(max) -Maximum average forward current. (Heat sink)
• Surge Current IS - maximum forward surge current, not
exceeding one cycle
• Peak Reverse Voltage PRV or Peak Inverse Voltage PIV (same)
The maximum reverse voltage that can be applied to a diode.
The diode will break down if this value is exceeded.
Revision 01 11

12. p-n junction diodes
The leads of a diode,
form a heat sink. If these
Diode marking leads are cut shorter the
indicates current rating of the
Cathode diode must be reduced.
The epoxy casing is for
A semiconductor strength and works as a
heat sink.
device that has one p-n
junction is the p-n
junction diode. Standard
symbol
Anode (A)
Common
non-
standard
symbols Cathode (K)
Revision 01 12

13. Diode testing with analogue
multimeter
Ohmmeter Ohmmeter
M 0
I
I