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 are

a.

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 differen

ces 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 cat

hode 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—Powe

r 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 th

ose 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 eve

n 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 tur

n- 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 19

97 by ABBActually the close integration of GTO and the gate drive circuit with multi

ple MOSFETs in parallel providing the gate currentsShort name: GCTConduction drop, gate driver loss, and switching speed are superior to GT

O 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