Chapter 1 Power Electronic Devices
Outline1.1 An introductory overview of power electronic devices
1.2 Uncontrolled device—power diode
1.3 Half- controlled device—thyristor
1.4 Typical fully- controlled devices
1.5 Other new power electronic devices
1.1 An introductory overview of power electronic devices
1) The concept and features Power electronic devices: are the electronic devices that can be directly
used in the power processing circuits to convert or control electric power.
Very often: Power electronic devices= Power semiconductor devices Major material used in power semiconductor devices——Silicon
In broad sense
Power electronic devices
Vacuum devices: Mercury arc
rectifier thyratron, etc. . seldom
in use today
Semiconductor devices:
major power electronic devices
Features of power electronic devices a) The electric power that power electronic device deals with is usually
much larger than that the information electronic device does.
b) Usually working in switching states to reduce power losses
c)Need to be controlled by information electronic circuits.
d)Very often, drive circuits are necessary to interface between information circuits and power circuits.
e)Dissipated power loss usually larger than information electronic devices —special packaging and heat sink are necessary.
On-state Voltage across the device is 0 p=vi=0
V=0
Off-state Current through the device is 0 p=vi=0
i=0
2) Configuration of systems using power electronic devices
Power electronic system:
Protection circuit is also very often used in power electronic system especially for the expensive power semiconductors.
Control circuit (in a broad sense)
Control
circuit
detection circuit
drive circuit
circuit
Power circuit (power
stage, main circuit)
Electric isolation:
optical, magnetic
Terminals of a power electronic device
Control signal from drive circuit must be connected between the control terminal and a fixed power circuit terminal (therefore called common terminal
A power electronic device usually has a third terminal — —control terminal to control the states of the device
C
G
E
A power electronic device must have at least two terminals to allow power circuit current flow through.
Drive Circuit
Major topics for each device
Appearance, structure, and symbol
Physics of operation
Specification
Special issues
Devices of the same family
Passive components in power electronic circuit
Transformer, inductor, capacitor and resistor: these are passive components in a power electron
ic circuit since they can not be controlled by control signal and their characteristics are usually constant and linear.
The requirements for these passive components by power electronic circuits could be very different from those by ordinary circuits.
1.2 Uncontrolled device Power diode
Appearance
PN junction
- -
- -
-
- -
-
- - - -
- - - -
- - - -
+ + +
+
+
+
+ + +
+ +
+
+ + + +
+ + + +
p region
Space charge
Region
(depletion region,
potential
barrier region)
n region
Direction of
inner electric field
PN junction with voltage applied in the forward direction
V
+ -
p n
W
WO
- -
- -
-
+ +
+
+
+
PN junction with voltage applied in the reverse direction
V + -
p n
W
WO
- -
- -
-
+ +
+
+
+
Effective direction of electronic field
Construction of a practical power diode
+
V
-
Anode
Cathode
Na =10 cm
19 -3
P +
Nd =10 cm
-3
Nd =10 cm
19 -3
-3 14 n +
- n
epi
substrate
10μm
250μm
Breakdown Voltage dependent
Features different from low-power (information electronic) diodes
–Larger size
–Vertically oriented structure
–n drift region (p-i-n diode)
–Conductivity modulation Junction capacitor The positive and negative charge in the depletion region is variable with the
changing of external voltage. variable with the changing of external voltage.
—–Junction capacitor C Junction capacitor CJ .
Junction capacitor influences the switching characteristics of
power diode.
Junction capacitor CJ
Potential barrier capacitor CB
Diffusion capacitor CD
Static characteristics of power diode
Turn-off transient Turn- on transient
IF
I
O UTO UF U
I F
U F
t F t 0
t rr
t d t f
t 1 t 2 t U R
U R
P
I R
P
d i F
d t
d i R
d t
U FP
u
i i F
u F
t fr t 0
2V
Examples of commercial power diodes
part number Rated vag current VF(typical) tr(max) Rated max voltage
Fast recovery rectifiers
1N3913
SD453N25S20PC
MUR815
MUR1560
RHRU100120
Ultra-fast recovery rectifiers
Schottky rectifiers
MBR6030L
444CNQ045
30CPQ150
400V
2500V
150V
600V
1200V
30V
45V
150V
30A 400A
8A
15A
100A
60A
440A
30A
1.1V
2.2V
0.48V
1.19V
0.69V
0.975V
2.6V
1.2V
400ns
20μ s
35ns
6ns
60ns
1.3 Half- controlled device—Thyristor
Another name: SCR—silicon controlled rectifierThyristor Opened the power electronics era–1956, invention, Bell Laboratories–1957, development of the 1st product, GE–1958, 1st commercialized product, GE–Thyristor replaced vacuum devices in almost every power processing
area.
Still in use in high power situation. Thyristor till has thehighest power-handling capability.
Appearance and symbol of thyristor
Structure and equivalent circuit of thyristor
P 1
A
G
K
N 1
P 2 P 2
N 1
N 2
a)
NPN
PNP
A
G
K
I G
I K
I c2
I c1
I A
V 1
V 2
b)
Structure
Equivalent circuit
Equivalent circuit
Physics of thyristor operation
R
NPN
PNP
A
G
S
K
E G
I G
E A I K
I c2
I c1
I A
V 1
V 2
Equivalent circuit: A pnp transistor and an npn
transistor interconnected together
Positive feedback
Trigger
Can not be turned off by control
signal
Half-controllable
Quantitative description of thyristor operation
When IG =0, α1+α2 is small.
When IG >0, α1 +α2 will approach 1, IA will be very large.
I c1=α 1 IA + I CBO1 (1-1) I c2= α 2 IK + I CBO2 (1-2)
IK=IA+IG (1-3)
IA=Ic1+Ic2 (1-4)
(
I I I
) 1 2 1
CBO2 CBO1 G 2 A
I ( 1-5 )
Other methods to trigger thyristor on
High voltage across anode and cathode—avalanche breakdown
High rising rate of anode voltagte —du/dt too high
High junction temperature
Light activation Static characteristics of thyristor
Blocking when reverse biased, no matter if there is gate current applied.
Conducting only when forward biased and there is triggering current
applied to the gate.
Once triggered on, will be latched on conducting even when the gate current is no longer applied.
Switching characteristics of thyristor
100% 90%
10%
u AK
t O
0 t d t r
t rr t gr U RRM
I RM
i A
t
1.4 Typical fully- controlled devices
Features
–IC fabrication technology, fully- controllable, high frequency
Applications
–Begin to be used in large amount in 1980s
–GTR is obsolete and GTO is also seldom used today.
–IGBT and power MOSFET are the two major power
semiconductor devices nowadays.
1.4.1 Gate- turn- off thyristor—GTO
Major difference from conventional thyristor:The gate and cathode structures are highly interdigitated , with various types
of geometric forms being used to layout the gates and cathodes.
Physics of GTO operation The basic operation of GTO is the
same as that of the conventional thyristor. The principal
differences lie in the modifications in the
structure to achieve gate turn- off capability.
–Large α2 –α1+α2 is just a little larger than
the critical value 1. –Short distance from gate to
cathode makes it possible to drive current out of gate.
R
NPN
PNP
A
G
S
K
E G
I G
E A I K
I c2
I c1
I A
V 1
V 2
1.4.2 Giant Transistor—GTR
GTR is actually the bipolar junction transistor that can handle
high voltage and large current.
So GTR is also called power BJT, or just BJT.
Structures of GTR different from its information-processing counterpart
Static characteristics of GTR
cut-off region
Amplifying (active) region
Saturation region
O
I c
i b3
i b2
i b1
i b1 < i b2 < i b3
U ce
Second breakdown of GTR
O
i c
U CE
IB=0
IB5
IB4
IB1
IB2
IB3 Active region
Second breakdown
Quasi-saturation Hard
saturation 1 -
R d
Primary
breakdown
IB5 >IB4. etc.
IB<0
IB=0
BVCEO BVCBO
BVSUS
1.4.3 Power metal- oxide- semiconductor field effect transistor—
Power MOSFET A classification
Basic structure Symbol
Field Effect Transistor (FET)
Metal- onside-semiconductor FET (MOSFET)
Power MOSFET
Junction FET (JFET)
Static induction transistor (SIT)
n channel
p channel
N channel
G
S
D
G
S
D
P channel
Physics of MOSFET operation (Off- state)
p-n- junction is
reverse-biased
off-state voltage
appears across
n- region
Physics of MOSFET operation (On-state)
p-n- junction is slightly reverse biased positive gate voltage induces conducting channel drain current flows through n- region an conducting channel on resistance = total resistances of n- region,conducting channel,source and drain contacts, etc.
Static characteristics of power
O
iD
UDS
Ohmic
[UGS-VGS(th)=UDS]
VGS5
VGS1
VGS2
VGS3
VGS4
Active
Cut off
VGS< VGS(th)
BVDSS
VGS5> VGS4 etc.
Switching characteristics of power MOSFET
Turn- on transient Turn- off transient
–Turn- on delay time td(on) –Turn- off delay time td(off)
–Rise time tr –Falling time tf
R s
R G R F
R L
i D
u GS
u p i D
+ U E
i D
O
O
O
u p
t
t
t
u GS u GSP u T
t d (on) t r t d (off) t f
Examples of commercial power MOSFET
p art n u m b er R ated vag cu rren t Q g(typ ica l) R on R ated m ax vo ltage
IR F Z 48
IR F 510
A P T 105M 25B N
R IR F 740
M T M 15N 40E
A P T 5025B N
A P T 1001R B N R
60V
100V
100V
400V
400V
500V
1000V
50A 5 .6A
28A
75A
10A
15A
23A
11A
0 .018Ω
0 .54Ω
0 .3Ω
1 .0Ω
0 .25Ω
0 .077Ω
0 .55Ω
0 .025Ω
IR F 540 100V
110n C
8 .3 nC
171 nC
8 .3 n C
63 nC
11 0 nC
72 nC
83nC
150 nC
1.4.4 Insulated- gate bipolar transistor—IGBT Combination of MOSFET and GTR
GTR: low conduction losses (especially at larger blocking volta ges),
longer switching times, current- driven
MOSFET : faster switching speed, easy to drive (voltage- driven),
larger conduction losses (especially for higher blocking voltages)
IGBT
Features On- state losses are much smaller than
those of a power MOSFET, and are comparable with those of a GTR
Easy to drive —similar to power MOSFET
Faster than GTR, but slower than power MOSFET
Structure and operation principle of IGBT
Also multiple cell structure Basic structure similar to power MOSFET, except extra p region On- state: minority carriers
are injected into drift region, leading to conductivity modulation
compared with power MOSFET: slower switching times, lower on- resistance, useful at higher voltages (up to 1700V)
E G
C
N + N
- P
N + N + P
N + N +
P +
Emitter
Gate
Collector
Injecting layer
Buffer layer
Drift region
J 3 J 2
J 1
Equivalent circuit and circuit symbol of IGBT
G
E
C
+
- + -
+
-
I D R N
I C
V J1
I D R on G
C
E
Drift region resistance
Switching characteristics of IGBT
t
t
t
current tail
UGEM UGE 90%UGEM
10%UGEM 0
0
0
ICM IC 90%ICM
10%ICM
UCE UCEM
UCE(on)
t on
t fv1
t off
t d(on)
t fv2
t fi1 t fi2
t f t r t d(off)
Examples of commercial IGBT
part number Rated avg current tf(typical) VF(typical
)
Rated max voltage
Single-chip devices
HGTG32N60E2
multiple-chip power modules_
CM400HA-12E
CM300HA-24E
600V
1200V
600V
1200V
32A
30A
2.4V
3.2V HGTG30N120D2
0.62μ s
0.58μ s
400A
300A
2.7V
2.7V 0.3μ s
8.3 nC
0.3μ s
1.5 Other new power electronic devices
Static induction transistor —SITStatic induction thyristor —SITHMOS controlled thyristor —MCTIntegrated gate- commutated thyristor —IGCTPower integrated circuit and power module1) Static induction transistor—SITAnother name: power junction field effect transistor—power JFET Features–Major- carrier device–Fast switching, comparable to power MOSFET–Higher power- handling capability than power MOSFET–Higher conduction losses than power MOSFET–Normally- on device, not convenient (could be made normally- off, but with
even higher on-state losses)
2) Static induction thyristor—SITH
other names–Field controlled thyristor—FCT
–Field controlled diode
Features–Minority- carrier device, a JFET structure with an additional
injecting layer
–Power- handling capability similar to GTO
–Faster switching speeds than GTO
–Normally- on device, not convenient (could be made
normally- off, but with even higher on- state losses)
3) MOS controlled thyristor—MCTEssentially a GTO with integrated MOS- driven gates controlling both
turn- on and turn- off that potentially will significantly simply the design of circuits using GTO.
The difficulty is how to design a MCT that can be turned on and turned off equally well.
Once believed as the most promising device, but still not commercialized in a large scale. The future remains uncertain.
4) Integrated gate- commutated thyristor — IGCTThe newest member of the power semiconductor family, introduced in
1997 by ABBActually the close integration of GTO and the gate drive circuit with
multiple MOSFETs in parallel providing the gate currentsShort name: GCTConduction drop, gate driver loss, and switching speed are superior to
GTO Competing with IGBT and other new devices to replace GTO
Review of device classifications
power electronic devices
Current- driven (current- controlled) devices: thyristor, GTO, GTR
Voltage- driven (voltage- controlled) devices (Field- controlled devices):power MOSFET,IGBT, SIT, SITH, MCT, IGCT
power electronic devices
Pulse- triggered devices: thyristor, GTO
Level- sensitive (Level- triggered) devices: GTR, power MOSFET, IGBT, SIT, SITH,MCT, IGCT
power electronic devices
Uni- polar devices (Majority carrier devices): SBD, power MOSFET, SIT Bipolar devices (Minority carrier devices): ordinary power diode, thyristor, , GTO, GTR, IGCT, IGBT, SITH, MCT
Composite devices: IGBT, SITH, MCT
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