Indo German Meet
Project Title
IGBT’s Characteristics & Technology
-Ganesh Bhalsing (06EE3009)
-IIT Kharagpur
- Under Guidance of Prof. H. Ryssel
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Agenda
 Introduction
Different Power Transistors
Comparison Between all Types of Power Transistors
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Agenda
 Introduction
 Power Electronic Devices
 Characteristics of an Ideal Switch
 Some Practical uses of Switches
 Classification of Power Semiconductors
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Introduction
Power Electronic Devices
Power semiconductor devices are the essential components
determining the size, cost, efficiency of electronic systems
for energy efficiency
The proliferating demand of controllable power electronic
systems has promoted research on
 Novel device materials
 Structures
Circuit topologies
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Introduction
Power Electronic Devices
Base material used for power electronics devices –
 Silicon
 Silicon Carbide
Silicon
Silicon Carbide
Breakdown Field
2.5 ×105 V/cm
2.2 ×106 V/cm
Energy gap
1.12 eV
3.26 eV 4H-SiC
Thermal Conductivity
1.5 W/cm
4.9 W/cm
Also SiC shows high chemical inertness, high pressure, and radiation
resistance and hence its popular in the recent days
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Indian Institute of Technology, Kharagpur
IGBT’s Characteristics &
Technology
Introduction
Characteristics of Ideal Switch
 No driving losses : High input impedance so that the drive
current is zero
 Zero on state or forward conduction losses : forward voltage
drop is zero & high operational current density to make chip small
 Zero off state or reverse blocking losses : Infinitely larger
reverse blocking voltage with zero leakage current
 No switching losses : turn on and turn off times should be
zero. A small pulse of small width, tending to zero, must be used for
the operations
 Low Cost : To reduce the cost of the electronic equipment
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Introduction
Some Practical uses of Switches
 PWM control in DC motor control
 Rectifiers
 Air Conditioners
and many more
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Introduction
Some Practical uses of Switches
DC motor control :
RA
+
Vf
-
Armature
Va
Field Coil
Motor used – Self excited DC motor
• Flux is constant
• Speed is controlled by varying Armature voltage (Va)
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Introduction
Some Practical uses of Switches
DC motor Control :
Equations of DC motor modelling
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Introduction
Some Practical uses of Switches
DC motor control :
Using the switch to control PWM (Pulse Width Modulation),
Thus controlling Va and hence effective DC voltage supplied to motor
Ref: 1
PWM generation using a switch
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Introduction
Some Practical uses of Switches
3 Phase full bridge rectification :
Input Circuit
Output Waveform
Ref: http://www.allaboutcircuits.com/vol_3/chpt_3/4.html
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IGBT’s Characteristics &
Technology
Introduction
Classification of Power Semiconductors
Classification of Power
Semiconductors
Ref: 1
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Agenda
Introduction
 Different Power Transistors
Comparison Between all Types of Power Transistors
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
Different Power Transistors
 BJT
 MOSFETs
 Insulated Gate Bipolar Transistors
 Static Induction Transistors (SIT)
 COOLMOS
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
Power transistors
Controlled Turn-on & Turn-off Characteristics :
Power transistors have controlled turn-on and turn-off characteristics
Region of Operation :
Transistors used as switches are generally used in the saturation region,
resulting in low on-state voltage drop
Ratings :
These power transistors come with varying switching frequencies and
with different current and voltage ratings
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
1.BJT’s (Bipolar Junction Transistors)
Construction :
Ref: 1
Basic NPN transistor constructional design
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
1.BJT’s Input/Output Characteristics
Output Characteristics
Input Characteristics
Ref: 1
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
1.BJT’s Transfer Characteristics of Switch
Transfer Characteristics of
switch
Circuit diagram
(common emitter)
Ref: 1
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
1.BJT’s Switching Characteristics
Switching times of BJT
Model with current gain
Ref: 1
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
1.BJT’s Switching Limits
Second Breakdown (SB) :
Destructive phenomenon due to current flow only to small
region of the base producing local hot spots.
Breakdown Voltage :
Voltage between two terminals for which the current rises
rapidly irrespective of rise in voltage level.
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
2.Power MOSFETs
 A voltage controlled device
Overcoming problems of BJT
 BJT being current controlled, current gain depends on junction
temperature but this problem is removed in MOSFET
 Very high input impedance hence low current
 No problem of second breakdown phenomenon
 High switching speed i.e. low switching time since voltage
controlled
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
2.MOSFETs Construction
‘n’ channel
depletion type
Ref: 1
‘n’ channel
enhancement Type
Ref: 1
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
2.MOSFETs Transfer Characteristics
‘n’ channel
depletion type
Ref: 1
‘n’ channel
enhancement type
Indian Institute of Technology, Kharagpur
Ref: 1
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IGBT’s Characteristics &
Technology
Different Power
Transistors
2.MOSFETs Output Characteristics
‘n’ channel enhancement type
Ref: 1
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
2.MOSFETs Switching Characteristics
Parasitic model of
enhancement MOSFET
Switching characteristics
Ref: 1
Indian Institute of Technology, Kharagpur
Ref: 1
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IGBT’s Characteristics &
Technology
MOSFET
Different Power
Transistors
BJT
Ref: 1
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBT (Insulated Gate Bipolar Transistor)
 It combines the properties of both
BJT
– Low on state conduction losses &
MOSFET - High input impedance
Various other names are  COMFET (Conductivity Modulated FET)
 IGT
(Insulated Gate Transistor)
 IGR
(Insulated Gate Rectifier)
 GEMFET (Gain enhanced MOSFET)
 BiFET
(Bipolar FET)
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBTs - construction
Unit Cell
Ref: 2
 It is identical to that of MOSFET except the doping on the Nsubstrate
 Performance close to that of a BJT than a MOSFET
 Four alternate PNPN layer
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBTs – equivalent circuit representation
Ref: 2
 N channel enhancement mode MOSFET driving a PNP bipolar transistor
 Presence of gate, collector and emitter
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBTs – Output & Transfer Characteristics
Ref: 2
Ref: 1
Output Characteristics
Gate- emitter characteristics
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBT’s Switching Characteristics
Turn on characteristics
 Turn on takes place by voltage
 Low gate power requirement means that computer-controlled
signals from integrated driver circuits can be used
 IGBT turn on is slower than the MOSFET because of the necessity
of forcing both the MOSFET and BJT inside it
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBT’s Switching Characteristics
Ref: 2
 IGBT turn on with a resistive load
 When the gate voltage equals the threshold voltage Vth, the
collector-emitter current Ice begins to flow and rises rapidly
according to the transconductance parameter gm
 Eon= (Vs × I × Tc)/6
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBT’s Switching Characteristics
Turn off
characteristics
Ref: 2
 As soon as the gate voltage ceases IGBT turns off – time to decay of
collector current from 90% to 10%
 Decay time is composed of two halves. One due to discharge of
current across Rge and Cge and second (time consuming one ) due to
recombination in the N- base
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Indian Institute of Technology, Kharagpur
IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBT’s Switching Characteristics
Ref: 2
Effect of increasing
gate resistance
Effect of increasing
electron dose in the N- base
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBT’s Switching Characteristics
Ref: 2
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
3.IGBTs – Device Structures
Different Power
Transistors
Lateral IGBT
Ref: 2
 Used for integration with devices for control security
 No JFET region is present
Block voltage in both directions, due to back to back p-n junction
 More surface area used
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBTs – Device Structures
Ref: 2
Non - Punctured Type
Indian Institute of Technology, Kharagpur
Ref: 2
Punctured Type
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBTs – Device Structures
Punctured Type
Non Punctured Type
Heavily doped n layer
Switching time is reduced
More fragile than punctured
Current flow via diffusion
Based on growing thick
epitaxial layer on p+ substrate
Less thermally stable
Moderately doped
Carrier lifetime is kept more
Less fragile
Current flow by drift
Based on thin wafer technology.
More thermally stable
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBTs – Device Structures
Self Clamped IGBT
Equivalent Circuit
Ref: 2
 Has integrated gate collector clamp diodes for IGBTs
protection
 Used in automotive ignition system where it acts as a driver
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBTs – Device Structures
Trench Gate IGBT
Ref: 2
Ref: 2
Injection enhanced IGBT
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Indian Institute of Technology, Kharagpur
IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBTs – Technologies
Trench Type IGBT
 Normal IGBT suffers from electric current crowding and
electric field crowding
 Current crowding reduces the conductivity modulation
Solution
 Increase the gate length, for more conductivity modulation
 decrease the path travelled by electrons under the emitter
region
 Trench Gate has no JFET region hence minimizes on state losses
 The U shaped trench decreases the path
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBTs – Device Structures
Larger injection of electron from
N channel to N-base
 Hole current is suppressed
 Small forward voltage drop
Ref: 2
Injection enhanced IGBT
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
3.IGBTs – Device Structures
Different Power
Transistors
Resurf Technology
Reduced surface electric field (Resurf concept)
for breakdown Voltage enhancement in Lateral IGBT
High resistive P- substrate
Epitaxial N- layer over it
Laterally bounded by a P+ diffused region
2 diodes : Horizontal P-N- and vertical P+NBreakdown occurs at the core rather than surface
By choosing proper conditions
Ref: 2
Thus using high ohmic contacts and thin epitaxial
layers and satisfying above condition break down
voltage can be increased
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBTs – Modes of Operation
Reverse Blocking
Ref: 2
Positive voltage is applied to N+emitter
Negative bias is applied to the P+collector
Gate terminal is shorted to the emitter terminal
J1 and J3 are reverse biased and J2 is forward biased. The resistivity and
thickness of the N- base must therefore be optimized for the required
breakdown voltage
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBTs – Modes of Operation
Forward Blocking Mode
Negative voltage is applied to N+emitter
Positive bias is applied to the P+collector
Gate terminal is shorted to the emitter terminal
Ref: 2
J1 and J3 are forward biased and J2 is reverse biased. Most of the depletion
layer expands into N- base
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBTs – Modes of Operation
Forward Conduction Mode
Ref: 2
Negative voltage is applied to N+emitter
Positive bias is applied to the P+collector
Positive bias to gate terminal
N type conducting channel formed in the P – base region bridges across the
N+ emitter and N- base
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
3.IGBTs – Protection
Overvoltages :
 During the blocking state, any applied voltage in excess of the breakdown
voltage between collector and emitter terminals causes avalanche breakdown
 Attach voltage arrestor in parallel to the IGBT
 If the reverse blocking voltage of IGBT is small, a reverse connected diode
placed across the IGBT is helpful
Overcurrents :
 Overcurrent is the current value at which junction temperature becomes
more than 150°C
 When an overcurrent is sensed, the gate voltage is decreased by switching a
zener diode across the gate terminal within a short time interval of 1μsec
Transients :
 Ramp waveform or a two step-waveform replaces the conventional stepped
voltage waveform
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
4.COOLMOS
Ref: 3
Recently a new technology for high voltage Power MOSFETs has been introduced CoolMOS
CoolMOS™ virtually combines the low switching losses of a MOSFET with the on-state losses
of an IGBT
The drastically lower gate charge facilitates and reduces the cost of controllability
the smaller feedback capacitance reduces the dynamic losses
Also very less R(ds) on state
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
5. SITs (Static Induction Transistors) - construction
Ref: 1
 Vertical structure with short multi-channels
 Identical to JFET except for vertical and buried gate
 Short channel length – low gate resistance, low gate-source
capacitance, small thermal resistance
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
5. SITs - Output Characteristics
Ref: 1
 Its typically an ON device and a negative gate voltage holds it off
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
5. SITs
Characteristics
 High power, high frequency device
 Turn-on and turn-off times are very small, typically 0.25 µ secs
 On-state drop as high as 90 V for 180 A device & 18 V for 18 A
 Work on power with 100KVA at 100 kHz or 10 VA at 10GHz
 Most suitable for high power, high frequency, applications (audio,
microwave amplifiers)
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
Introduction
Different Power Transistors
 Comparison Between all Types of Power Transistors
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Comparison Chart
Indian Institute of Technology, Kharagpur
Different Power
Transistors
Ref: 1
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IGBT’s Characteristics &
Technology
Different Power
Transistors
Thank You
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IGBT’s Characteristics &
Technology
References :
1.
2.
3.
4.
Different Power
Transistors
‘Power Electronics – Circuits, devices, and applications’ , Third Edition 2007,
by Muhammad H. Rashid
IGBT – Theory and Design, by Vinod Kumar Khanna, IEEE Press, 2003
‘COOLMOSTM-a new milestone in high voltage power MOS’ – Paper presented
in ‘Power Semiconductor Devices and ICs, 1999. ISPSD '99. Proceedings’, The
11th International Symposium, publication date: 1999
‘Solid State Electronic Devices’, Sixth Edition 2007, by Ben G. Streetman &
Sanjay Kumar Banerjee
Indian Institute of Technology, Kharagpur
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IGBT’s Characteristics &
Technology
Different Power
Transistors
Questions ?
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