Chapter 1
Introduction to Power
Electronics/ Power
Semiconductor Devices
Learning Outcomes
• At the end of this topic, students
should be able to
1) outline functions and related issues of
power electronics applications,
2) identify power semiconductor devices,
and
3) describe the characteristic of power
semiconductor devices and their drive
requirements.
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Introduction to Power
Electronics (PE)
• PE circuits involve in converting
electrical power from one form to
another using power semiconductor
devices.
• The conversion of power can occur in
uncontrollable or controllable
manner.
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• PE circuits are known as converters.
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Introduction to Power
Electronics (PE)
Block diagram of power conversion using PE circuits/ converters
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Goal of PE
• To convert electrical power according to
application demand.
• Power is converted with
– high efficiency,
– high availability,
– high reliability,
– lowest cost,
– smaller size, and
– lightest weight.
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Application of PE
1. Static application.
– Involving non-rotating mechanical components.
Examples: rectifiers, inverters and etc.
– To convert electrical power for supplying load
demand or for Power Quality (PQ) improvement.
2. Drive application.
– Involving rotating mechanical components.
Examples: AC or DC motor drives.
– To manipulate certain parameter for controlling
the speed of motors.
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Current Issues Related to PE
1. Energy scenario.
– Increase the use of renewable energy such as
solar and wind energy.
– Reduce the dependency to fossil fuel and
nuclear power.
– Improve PQ and energy saving.
2. Environment issues.
– Nuclear safety radioactive.
– Air pollution due to fossil fuel combustion.
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Growth Factors of PE
Application
1. Advances in power semiconductor devices:
capability in handling high voltage or high
current.
2. Advances in controllers: efficiency and accuracy.
3. Advances in control algorithms: simple and
accurate.
4. High demand for new PE applications.
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PE Converters
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Introduction to Power
Semiconductor Devices
• These devices are used in any power electronic
circuits as switches for conducting electrical
current.
• Hence, they also can be called as power switches.
• Their operation can be either uncontrollable or
controllable.
• A single unit of power switches conducts current in
one direction only.
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Introduction to Power
Semiconductor Devices
http://www.iue.tuwien.ac.at/phd/park/node14.html
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Ideal Versus Practical Power
Switches
Ideal switch Practical switch
During off- Block arbitrarily large Finite blocking forward
state forward voltage and voltage and reverse
reverse voltage with voltage with small current
zero current flow. flow.
During on-state Conduct arbitrarily Finite forward current flow
large forward current and considerable voltage
with zero voltage drop. drop.
Switching Switch from on-state to Require finite time (or time
activity off-state and vice versa delay) to reach maximum
instantaneously. voltage and current.
Gate signal (if Very small power is Depending on the type of
any) required from a control power switches, some of
source to trigger the them require small power
switch operation. (such as IGBT & MOSFET)
and some of them (such as
GTO) require substantial 12
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current to trigger their
Power Diodes
• The simplest power switches.
• Their operation is uncontrollable and it depends by
voltages and currents.
• When current flow from
anode to cathode, the diode is in https://learn.sparkfun.com/tutorials/diodes
forward-biased (on).
• When current flow form
cathode to anode, the diode is in
reverse-biased (off). http://my.element14.com/fairchild-
semiconductor/1n4148/diode-100v-200ma-do-
35/dp/9843680?MER=bn_browse_1TP_MostPopular_1
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Power Diodes
http://www.electronics-tutorials.ws/diode/diode_4.html
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Power Diodes
• To increase the reverse blocking
capability = connect several diodes
in series.
• To increase higher current
conductivity = connect several
diodes in parallel.
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Power Diodes
• When a diode turns off, the leakage current in
it decreases until negative value before
returning to zero.
• The time taken for the current to become zero
is known as reverse recovery time trr. The
current is known as reverse recovery current.
• Small trr is important in high frequency
applications.
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Power Diodes
https://www.allaboutcircuits.com/technical-articles/a-review-on-power-
semiconductor-devices/
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Power Diodes
• Effects of trr :
– Switching losses.
– Voltage ratings.
– Voltage spikes.
– Inductive loads.
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Power Diodes
Diode trr Voltage & current Application
ratings
General High ≈ High (up to 5 kV, 5 kA) Low switching
purpose 25 s frequency
diode applications such as
rectifiers and line
commutated
converters.
Fast- Low < 5 Medium (typically, High switching
recovery s from 50 V to around 3 frequency
diode kV, and from less than applications such as
1 A to hundreds of DC-DC and DC-AC
amperes. converters.
Schottky Very low Low voltage (around Low voltage and
diode ≈0 100 V) and high high current
current (from 1 A to applications such as
400 A) DC power supplies.
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Power Transistors
• Controllable power switches that operate in the
saturation region.
• Can be turned on and off using relatively very
small control signals; using driver circuits.
• Their voltage and current ratings are lower than
thyristors.
• They are normally used in low- to medium-power
applications.
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Power Transistors
• 3 common types:
1) Bipolar Junction Transistor (BJT),
2) Metal Oxide Semiconductor Field Effect
Transistor (MOSFET), and
3) Insulated Gate Bipolar Transistor
(IGBT).
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Power Transistors
V-I characteristics of BJTs V-I characteristics of IGBTs
V-I characteristics of MOSFE
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Power Transistors (BJTs)
• They operate as current controlled devices.
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Power Transistors (BJTs)
http://www.electronics-
tutorials.ws/transistor/tran_2.html
V-I characteristics of BJTs
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Power Transistors (BJTs)
• Ratings:
– Voltage: VCE < 1500 V.
– Current: IC < 600 A.
– Switching frequency up to 5 kHz.
– Low on-state voltage: VCE(sat): 2 – 3 V.
• Switching operation:
– Turn-on = inject + or - IB for NPN or PNP base terminal.
– Turn-off = remove IB.
• Not popular in new products.
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Power Transistors (BJTs)
• Advantage:
– Low on-state voltage.
• Disadvantages:
– Low current gain = IC / IB which is
commonly less than 10.
• We can use darlington pair to increase .
– Long turn off time.
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Power Transistors (BJTs)
• Darlington pair
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Power Transistors
(MOSFETS)
• They operate as voltage controlled devices.
http://my.element14.com/fairchild-
semiconductor/rfp30n06le/mosfet-
n-logic-to-220/dp/1017798?
ost=RFP30N06LE&selectedCategory
Id=&categoryNameResp=All&searc
hView=table&iscrfnonsku=false
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Power Transistors
(MOSFETS)
http://www.electronics-tutorials.ws/transistor/tran_7.html
V-I characteristics of MOSFETs
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Power Transistors
(MOSFETS)
• Ratings:
– Voltage: VDS <500 V.
– Current: IDS <300 A.
– Switching frequency (>100 kHz).
– High on-state voltage drop.
• Switching operation:
– Turn-on = apply VGS +15 V.
– Turn-off = apply VGS 0 V.
• Commonly for low voltage applications.
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Power Transistors
(MOSFETS)
• Advantages of MOSFETs over BJTs:
– Simpler gate drive requirement.
– Higher switching frequency.
– Higher positive temperature coefficient.
– Higher gain.
– No second breakdown phenomena.
• Disadvantages:
– Has electrostatic discharge problem.
– Has internal resistance between drain and source during
on-state, RDS(ON).
– Low voltage and current ratings.
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Power Transistors (IGBTs)
• They inherit the advantages of BJTs and MOSFETs.
– Voltage controlled devices (like MOSFETs)
– High input impedance (like MOSFETs).
– Easy to turn on and off (like MOSFETs).
– Low on-state conduction losses (like BJTs).
http://www.newtoncbraga.com/index.php/
articles/16-how-they-work/347-isolated-
gate-bipolar-transistor-igbt-art112
http://my.element14.com/infineon/irg4bc40fpbf/igbt-to-
220/dp/9105018
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Power Transistors (IGBTs)
• However, the performance of the
IGBT is closer to a BJT than an
MOSFET.
• Very popular in new products.
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Power Transistors (IGBTs)
V-I characteristics of IGBTs
http://protorit.blogspot.my/2013/02/insulated-gate-
bipolar-transistor-igbt.html
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Power Transistors (IGBTs)
• Ratings:
– Voltage: VCE <3.3 kV.
– Current: IC <1.2 kA.
– Switching frequency up to 100 kHz (typically
used at 20 – 50 kHz).
– Low on-state voltage: VCE(sat): 2 – 3 V.
• Switching operation:
– Turn-on = apply +VGE.
– Turn-off = apply VGE 0 V.
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Power Transistors
• Comparison
between
BJTs,
MOSFETs &
IGBTs:
– Steady-
state
characterist
ics:
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Power Transistors
– Dynamic-state characteristic.
Turn-on Turn-of
Ids
Ice
Power BJT
IGBT
Power MOSFET
time
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Thyristors
• Also known as Silicon
Controlled Rectifier (SCR).
• They require gate signal to
turn-on during the forward-
biased). The gate signal is not
required after the conduction http://electronicspost.com/draw-
and-explain-the-v-i-
starts. characteristics-of-an-scr/
• However, they do not have
gate controlled turn-off
capability. http://my.element14.com
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thyristor-25a-800v-to-
Thyristors
V-I characteristics of thyristors
http://electronicspost.com/draw-and-explain-the-v-i-
characteristics-of-an-scr/
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Thyristors
• Once turn-on, they will conduct current until the
anode current remains positive and higher than
the holding value.
• They will turn-off when the anode current
becomes
negative (reverse-biased) due to
– natural commutation,
– forced commutation using external circuitary, or
– supply voltage cutoff.
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Thyristors
• Advantages of thyristors:
– High power handling capability.
– High voltage and current ratings.
– High current conductivity.
– High blocking voltage.
– High gain.
– Very low on-state resistance.
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Thyristors
• The regenerative or latching action of thyristors can be
demonstrated using two-transistor model of thyristor.
http://www.eng.uwi.tt/depts/elec/staff/rdefour/ee33d/s4_
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Thyristors
• Consider a single transistor:
– IC is related to IE and ICBO as
---
(1)
where
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Thyristors
• For Q1, eqn. (1) becomes
---
(2)
• For Q2, eqn. (1) becomes
---
(3)
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Thyristors
• The sum of IC1 and IC2 yields IA.
---
(4)
• When gate current IG is applied to the
thyristor (forward biased),
---
(5)
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Thyristors
• Eqn. (5) eqn. (4). The result is
---
(6)
• Typical variation of
with IE.
--- For
Q1
--- For
Q2
http://www.eng.uwi.tt/depts/elec/staff/rdefour/ee33d/s4_
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Thyristors
• If the gate current IG is increased from 0 to some positive value, this will
increase the anode current IA as shown in (6).
• An increase of IA will increase IE1 and subsequently increase 1 shown in the
graph vs IE.
• According to (5), the increase of 1 will also increase 2.
• The increase values of both 1 and 2 would further increase the value of IA.
• This process is known as regenerative/ positive/ latching action.
• If 1 and 2 approach unity, the denominator of (6) approaches 0 and large
value of IA is produced and causing the thyristor to turn on as a result of
the application of a small IG.
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Thyristors
Thyristor Conduc Gate Gate Application
tion controlled controlled
turn-on turn-of
Phase 1 Yes No Low switching
control direction frequency
thyristor applications
(SCR) such as AC
and DC motor
drives.
Fast 1 Yes No (but it has High switching
switching direction fast turn-off frequency
thyristor time which is applications
(SCR) 5 - 50 s) such as
inverters and
choppers.
Light 1 Yes (in a form No Used in high
Activated direction of direct voltage and
Silicon radiation/
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Controlled pulse of RAHMAN
ABDUL applications
Thyristors
Thyristor Conduc Gate Gate Application
tion controlled controlled
turn-on turn-of
Bidirection 2 Yes No For low power
al Triode direction applications
Thyristor s (each such as AC
(TRIAC) antiparal phase control.
lel
thyristor
conducts
at
opposite
direction
Gate Turn- 1 Yes Yes (by For low and
Off direction applying fast switching
Thyristor negative gate applications.
(GTO) signal) Mostly used in
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converters.
Thyristors
• Advantages of GTOs:
– Eliminate commutating component in force
commutation.
– Faster turn-off time.
– Improve a converter efficiency.
• Disadvantages of GTOs:
– Has low gain during turn-off: high negative
gating signal.
– Has higher on-state voltage than SCRs.
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Types of Power
Semiconductor Devices
Power V-I Characteristic
switch
Diode Passes current in one direction and blocks in the other
direction.
BJT Passes or blocks current in one direction.
MOSFET Passes or blocks current in one direction.
IGBT Passes or blocks current in one direction.
Thyristor Passes current in one direction or blocks in both
directions.
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Pulse Transformers
• It has one primary winding
and one or more secondary
windings.
• It transfers signal in a form
of pulse.
http://www.directindustry.com
• It provides isolation between /prod/murata-power-
solutions/product-101149-
controller circuit and power 927585.html
circuit.
• It does not work with DC or
pure sinusoidal signal.
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Optocouplers
• It allows two circuits to exchange signal yet
remain electrical isolated.
• It can transfer DC signal, square pulse at a
very high speed.
• Standard circuit is using LED.
http://usources.manufacturer.globalsources.com/si/6008
800061742/pdtl/Microcontroller/1123509615/Optocouple
rs.htm
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Drive Circuits
• They act as interface between
control circuits and power switches.
• They amplify a control signal to a
level required to drive power
switches,
• They also provide electrical isolation
between control circuits and power
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switches; for protection.
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Power Losses in Power Switching
Devices
• The importance of power switch losses:
– To ensure system reliability.
– To specify an appropriate heat remover
mechanism.
– To improve an efficiency of the system.
• Main losses:
1. Forward conduction losses.
2. Blocking state losses.
3. Switching losses.
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Switching Losses
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Summary of Device
Capabilities
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Power Electronics Devices Application
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