The document introduces power electronics, detailing the author's educational background, professional experience, and course structure. It covers key concepts like power conversion, types of converters, and the functionality of electronic switches such as diodes and transistors. Applications and future trends in power electronics are also discussed, emphasizing the importance of efficient power management systems.

1. Introduction to Power Electronics
Source: Daniel Hart
Electrical Engineering
Muhammad Jafar

2. Personal Introduction
Academic
PhD electrical engineering, 2013, Norwegian University of Science & Technology
MSc electrical engineering, 2008, UET Taxila
BSc electrical engineering, 1998, NWFP UET Peshawar
Professional
2012 – 2018, DNV GL, A Norwegian multinational testing, inspection, certification, and
advisory company
2004 – 2008, CIIT Wah Cantt., Educational institution
1999 – 2004, Siemens Islamabad, A German multinational working in the electric power
products and projects business
Specialization
Electrical power engineering
Power electronics
HVDC, FACTS, renewable energy, microgrids

3. Course Information
Grading
Quiz (20%), sessinals (30%), and final (50%)
Absolute grading (means below 50% will fail)
Class rules
Mobiles switched off
Please be on time
Behavior
Please cooperate
Tolerate my tantrums! (I will try to be nice)
Provide feedback

4. Power engineering careers
Time/space Designer Supplier User
Pre-feasibility   
Feasibility   
Engineering   
Construction   
Operation   
De-commissioning   

5. Overview of applications of power electronics
Wikipedia article
Electrical4u article

6. Introduction to power Electronics
Power Electronics
Converter Classification
Power Electronics Concepts
Electronic Switches
Switch Selection
The Voltage-Controlled Switch
Transistors
Diodes
Thyristors (SCRs)

7. What we will discuss
What is Power Electronics?
The need for Power Conversion
Power Electronic Systems
Classification of Power Converter Circuits
Power Semiconductor Devices
Converter Modeling and Control
Applications of Power Electronics
Future Trends

8. Power Electronics
Power electronics?
Circuits that convert electric power from one form to another (AC/DC, DC/AC, DC/DC,
AC/AC).
Power electronics circuit function?
using semiconductor devices as switches
thereby controlling or modifying a voltage or current.

9. Electronics deals with
The semiconductor devices and circuits used in signal
processing to implement the control functions
Power deals with
Both static and rotating equipment that use electric
power
Control deals with
The steady-state stability of the closed-loop system
during the power conversion process

10. Convertor classification
The objective of a power electronics circuit
match the voltage and current requirements of the
load to those of the source.
Power electronics circuits convert one type or
level of a voltage or current to another
hence called converters.
Typical applications of power electronics
include
Rectification - Conversion of AC to DC
Inversion - Conversion of DC to AC
Conversion - Conversion of an unregulated DC
voltage to a regulated DC voltage
Cycloconversion - Conversion of an AC power
source from one amplitude and frequency to
another amplitude and frequency

11. Bidirectional converter
Power can go both ways
Multistep conversion
When just one converter cannot do the job

12. Power Electronics Concepts
Need 3-V DC voltage level across from a 9-V
battery
Simple solution using voltage divider ( and )
Issues
Power absorbed and lost by the resistor
Efficiency 33%
If changes and fixed, changes

13. Power Electronics Concepts
Possible solution
Using a transistor instead of to maintain 6V across
it and 3V across
Efficiency is low

14. Power Electronics Concepts
Solution: Fig (a)
Periodic opening and closing of the switch Fig (b)
Output: not a constant dc voltage
the average value is 1/3 of the source voltage
Power absorbed by switch
When closed ,
When opened ,
Efficiency=100%

15. Power Electronics Concepts
 Contains a DC term but is pulsating
To create a 3-V DC voltage, is applied to a low-pass (LP) filter
An ideal LP filter blocks pulsations and allows DC to pass
through
If the filter is lossless, the converter will be 100 percent
efficient

16. Power Electronics Concepts
System control
Outputs such as voltage and current are
measured, and operating parameters are
adjusted to maintain the desired output.
For example, if the 9-V battery output
decreases to 6 V, the switch would have to be
closed 50 percent of the time to maintain an
average value of 3 V for .
A feedback control system would detect if the
average output voltage is not 3 V and adjust
the closing and opening of the switch
accordingly

17. Electronic Switches
Two state device: On or off (ideally short-circuit or open circuit)
Short-circuit or on:
Switch voltage is zero
Zero power loss
Open-circuit or off
Switch current is zero
Zero power loss
Real switches are not ideal, but power loss is small

18. The Diode
Uncontrolled switch
Voltage and current dictate when it turns
on and when it turns off
Current reverses momentarily when
the diode switches off
Time associated is called reverse
recovery time (<1us)
Schottky diode: metal silicon barrier
instead of p-n junction
Faster
Smaller voltage drop
Reverse recovery transients absent

19. Thyristor
Controllable diode
Turn-on control
Turn-off not controlled externally
GTO is fully controllable
Also called silicon controlled
rectifier (SCR)
Can handle large voltage and
current
Relatively low frequency application
GTO needs significant current (1/3
of anode current) to switch off
Triac conducts current in either
direction (dimmer application)
MCT is similar to GTO but needs
smaller turn-off gate current

20. Transistors
Fully controllable
Several types
MOSFET
BJT
IGBT
MOSFET
Higher switching frequencies
than BJT
Turns on with gate voltage

21. Transistors
BJT
Turns on with base current
Needs sufficient base current
Power hungry
Darlington is a solution to high
base current requirement

22. Transistors
IGBT
Combination of MOSFET and BJT
Low power to switch on
Low on-state resistance
Have replaced BJTs in most applications

23. Switch selection
Controlling parameters
Voltage and current levels
Switching characteristics (fully controllable or not)
• Uncontrolled switching (Diode)
• Switch on only (SCR)
• Switch on and switch off both (Transistor, GTO)
Switching speeds
• MOSFET is better than BJT (lower switching losses)