WEEK 2

Semiconductor Power Switches

and

Supplementary Components and Systems

2

Semiconductor Power Switches

3

Power diode: (a) semiconductor structure, (b) circuit symbol

ANODE

CATHODE

(a)

p

n

A

(b)

C

V

I

4

Waveforms of voltage, current, and power loss in a semiconductor power switch

i

v

T

p = vi

tO N tO F F

t

t

5

Static voltage-current characteristic of the power diode

I

FMI VFM

VRB

IRM

V

6

Voltage and current waveforms during the reverse recovery period in a power diode

V

FI

F

i

v

R

V

RMV

rrt

rriI rrM

di rr

dt

t

7

Safe operating area for a power MOSFET

P E AK -CU R RE NT L IMIT

AVE R AG E -C U RR E N T LIM IT

V

ID

DS

P E AK -VO LTAG E LIM IT

O N -S TATE R E S IS TAN C E L IMIT

t =

t = 0.1 m s

t = 1 m s

SO A

TE MP E R ATU R E

LIM IT

8

TABLE 2.6 Properties and Maximum Ratings of Semiconductor Power Switches

_____________________________________________________________________________

Type Switching Switching Switching Forward Rated Rated Signal Characteristic Frequency Voltage Voltage Current

_____________________________________________________________________________

Diode 20 kHz1 1.2–1.7 V 6.5 kV 10 kA

SCR current trigger 0.5 kHz 1.5–2.5 V 8 kV 6 kA

Triac current trigger 0.5 kHz 1.5–2 V 1.4 kV2 0.1 kA2

GTO current trigger 2 kHz 3–4 V 6 kV 6 kA

IGCT current trigger 5 kHz 3-4 V 6.5 kV 6 kA

BJT current linear 20 kHz 1.5–3 V 1.5 kV 1.2 kA

MOSFET voltage linear 1 MHz 3–4 V 1.5 kV 1.8 kA

IGBT voltage linear 20 kHz 3–4 V 6.5 kV 2.4 kA

______________________________________________________________________________

1 Fast recovery diodes. General purpose diodes operate at 50 or 60 Hz.

2 BCTs (bi-directionally controlled thyristors), whose operating principle is similar to that of the triac, reach 6.5 kV of rated voltage and 5.5 kA of rated current.

9

Example diode and SCR modules

(d)

(c)

(a)

(b)

10

Example power MOSFET modules

(a)

(b )

(c)

11

IGBT-based modular frequency changer

SCR - Thyristor

• Some sources define silicon controlled rectifiers and thyristors as synonymous

• Other sources define thyristors as a larger set of devices with at least four layers of alternating N and P-type material.

12

13

TABLE 2.1 Example High-Power Diodes

______________________________________________________________________________

Symbol: RDK86040 R7014405 R9G23615 R6031635

(Powerex) (Powerex) (Powerex) (Powerex)

Type: General Purpose General Purpose Fast Recovery Fast Recovery

Case: Disc Stud Disc Stud

VRRM: 6 kV 4.4 kV 3.6 kV 1.6 kV

IF(av): 4 kA 0.55 kA 1.5 kA 0.35 kA

IF(rms): 6.3 kA 0.86 kA 2.35 kA 0.55 kA

IFSM: 60 kA 10 kA 18 kA 6 kA

I2t: 1.5×107 A2s 4.2×105 A2s 1.35×106 A2s 1.5×105 A2s

VFM: 1.65 V 1.2 V 1.65 V 1.5 V

IRRM: 300 mA 50 mA 75 mA 50 mA

trr: 25 µs 15 µs 5 µs 2 µs

Diameter: 132 mm 38 mm 74 mm 27 mm

Height: 38 mm 96 mm 28 mm 79 mm

______________________________________________________________________________

14

SCR: (a) semiconductor structure, (b) circuit symbol

ANO DE

CATHO DE

GATE

p

p

n

n

(a ) (b )

A

C

G

I

V

iG

15

Static voltage-current characteristic of the SCR

I

VVRB

VF B

FI VT M

IL

IH

iG > 0 iG = 0

16

SCR gate voltage signals(a) single pulse(b) multipulse

vG

t0

(a)

t0

(b)

17

Anode voltage and current waveforms during forced commutation of the SCR

V

FI

F

i

v

D

t

rrt

VR

V tOFF

18

TABLE 2.2 Example High-Power SCRs

______________________________________________________________________________

Symbol: 5STP 12N8500 5STP 50Q1800 C770L T7071430

(ABB) (ABB) (Powerex) (Powerex)

Type: Phase Control Phase Control Fast Switching Fast Switching

Case: Disc Disc Disc Stud

VRRM/VDRM: 8 kV 1.8 kV 2 kV 1.4 kV

IT(av): 1.2 kA 6.1 kA 2.1 kA 0.3 kA

IT(rms): 1.88 kA 9.6 kA 3.3 kA 0.475 kA

ITSM: 35 kA 94 kA 38 kA 8 kA

I2t: 6×106 A2s 4.3×107 A2s 6×106 A2s 2.65×105 A2s

VTM: 2 V 1.04 V 1.55 V 1.45 V

IRRM/IDRM: 400 mA/1 A 300 mA 100 mA 30 mA

tON: 3 µs 3 µs 2 µs 3 µs

tOFF: 600 µs 500 µs 100 µs 60 µs

IGT: 400 mA 400 mA 300 mA 150 mA

VGT: 2.6 V 2.6 V 3 V 3 V

Diameter: 150 mm 150 mm 110 mm 38 mm

Height: 35 mm 35 mm 37 mm 106 mm

______________________________________________________________________________

An SCR rated about 100 amperes, 1200 volts mounted on a heat sink - the two small wires are the gate trigger leads

19

SCR - Thyristor

• The thyristor is a four-layered, three terminal semiconductor device, with each layer consisting of alternately N-type or P-type material, for example P-N-P-N. The main terminals, labelled anode and cathode, are across all four layers. The control terminal, called the gate, is attached to p-type material near the cathode. (A variant called an SCS—Silicon Controlled Switch—brings all four layers out to terminals.) The operation of a thyristor can be understood in terms of a pair of tightly coupled bipolar junction transistors, arranged to cause a self-latching action:

20

Driver for an SCR with transformer isolation

21

SCR

PTR

D2

D1

DZ

(+)

TRA

22

• SCR - Thyristors can only be turned ON and cannot be turned OFF.

• Thyristors are switched ON by a gate signal, but even after the gate signal is de-asserted (removed), the thyristor remains in the ON-state until any turn-off condition occurs (which can be the application of a reverse voltage to the terminals, or when the current flowing through (forward current) falls below a certain threshold value known as the "holding current").

• Thus, a thyristor behaves like a normal semiconductor diode after it is turned on or "fired".

Thyristor stacks used for long distance transmission of power

from Manitoba Hydro dams

23

Optically isolated driver for an SCR

24

SCR

LED

LAT

OPTO-COUPLER

SCR crowbar for overcurrent protection of a power electronic converter

25

SOURCE

SUPPLY

CIRCUIT

CONTROL

CONVERTERAND LOAD

SCR

(+ )

(-)

R

26

TRIAC

27

TRIAC(a)semiconductor structure

(b) circuit symbol

G A T E

M A IN T E R M IN A L 2

M A IN T E R M IN A L 1

M T 2

M T 1

V

G

Ii G

(a) (b)

np

n

np

n

TRIAC TRIAC, from Triode for Alternating Current Conduct current in either direction when it is

triggered (turned on), and is formally called a bidirectional triode thyristor or bilateral triode thyristor.

TRIACs are part of the thyristor TRIACs are bidirectional and so current can flow

in either direction. TRIAC current flow can be enabled by either a

positive or negative current applied to its gate electrode

Continues to conduct until the current drops below a threshold – holding current.

Applying a trigger pulse at a controlled phase angle in an A.C. cycle allows control of the percentage of current that flows through the TRIAC to the load (phase control

Used in controlling the speed of low-power induction motors, in dimming lamps, and in controlling A.C. heating resistors.

28

Non-isolated driver for a triac

29

TR IA C

(+ )

TRA

Optically isolated driver for a triac

30

TRIAC

LAT

OPTO-COUPLER

R

LED

31

GTO - Gate Turn-Off Thyristor

GTO - Gate Turn-Off Thyristor (a) semiconductor structure, (b) circuit symbol

32

CATHO DE

GATE

A

C

G

(b )(a )

ANO DE

p

n

pn

Circuit symbol of the IGCT

33

I

V

A

C

iGG

Integrated Gate-Commutated Thyristor (IGCT)

An IGCT is a special type of thyristor similar to a GTO.

Have lower conduction loss as compared to GTOs, and withstand higher rates of voltage rise (dv/dt), such that no snubber is required for most applications.

The structure of an IGCT is very similar to a GTO thyristor.

In an IGCT, the gate turn off current is greater than the anode current.

This results in a complete elimination of minority carrier injection from the lower PN junction and faster turn off times. The main difference is a reduction in cell size, plus a much

34

Integrated Gate-Commutated Thyristor (IGCT)

The very high gate currents plus fast dI/dt rise of the gate current means that regular wires can not be used to connect the gate drive to the IGCT.

The drive circuit PCB is integrated into the package of the device.

The IGCT's much faster turn-off times compared to the GTO's allows them to operate at higher frequencies—up to several of kHz for very short periods of time.

Because of high switching losses, typical operating frequency up to 500 Hz.

35

36

TABLE 2.3 Example IGCTs

______________________________________________________________________________

Symbol: 5SHY42L6500 5SHY55L4500 5SHX19L6010 5SHX26L4510

(ABB) (ABB) (ABB) (ABB)

Type: Asymmetric Asymmetric Reverse Cond. Reverse Cond.

VDRM: 6.5 kV 4.5 kV 5.5 kV 4.5 kV

IT(av): 1.27 kA 1.86 kA 0.84 kA 1.01 kA

IT(rms): 2.00 kA 2.92 kA 1.32 kA 1.59 kA

ITSM: 26 kA 33 kA 18 kA 17 kA

I2t: 3.38×106 A2s 5.45×105 A2s 1.62×106 A2s 1.45×105 A2s

VTM: 2.0 V 1.15 V 1.9 V 1.8 V

IDRM: 50 mA 50 mA 50 mA 50 mA

tON: 40 µs 12 µs 11.5 µs 11.5 µs

tOFF: 40 µs 15 µs 14 µs 14 µs

IGQM: 4.2 kA 5.5 kA 1.8 kA 2.2 kA

Eoff: 44 J 31.5 J 11 J 12 J

Length: 429 mm 429 mm 429 mm 429 mm

Height: 40 mm 40 mm 40 mm 40 mm

Width: 173 mm 173 mm 173 mm 173 mm

______________________________________________________________________________

IGQM – maximum controllable turn-off gate current, Eoff – turn-off energy per pulse of gate current

Driver for a GTO - Gate Turn-Off Thyristor - with transformer

isolation

37

SCR

PTR

DZ

RCT

GT O

M1 M2

LC

(+)

Bipolar Junction Transistor

BJT

38

BJT(a) semiconductor structure(b) circuit symbol

39

COLLECT OR

EMIT TER

BASE

(a ) (b )

E

C

p

n

nV

IBCE

I

IC

E

B

Static voltage-current characteristic of the BJT

40

V

C E

IC

H A R D S A T UR A T IO N L IN E

Q U A S I-S A T UR A T IO N L IN E

ON

OFF

B

I

Base current and collector current waveforms for turn-on and turn-off of a BJT

41

IBIB0.9

IB t

i B

iI

I0.9C

C

C

IC0.1

0.1

t O FF

tO N

t

BJT Darlington connections: (a) two-transistor, (b) three-transistor

42

(a) (b)

C

E

B

C

E

B

Example power BJT (Darlington) modules

43

(c)

(a)

(b)

Totem-pole arrangement of two switches in a leg of a bridge topology

44

R

(+ )

(- )

The upper transistor is functioning as an active pull-up, in linear mode, while the lower transistor works digitally. For this reason they aren't capable of supplying as much current as they can sink (typically 20 times less). With two transistors stacked vertically, normally with a level shifting diode in between, they are called "totem pole" outputs.

A disadvantage of totem-pole outputs is that two or more of them cannot be connected together, because if one tried to pull while another tried to push, the transistors could be damaged. To avoid this restriction, some push–pull outputs have a third state in which both transistors are switched off. In this state, the output is said to be floating (or, to use a proprietary term, tri-stated).

45

BJT-based chopper with an RC snubber: (a) circuit diagram, (b) equivalent circuit in the off state

46

i

vL

i L

V i

snR C sn

vCE

BJT

ii

vo IoD

(a )

i

vL

i L

V i

snR C sn

vCE ii

vo I

(b )

o - i iIo

Voltage and current waveforms in the chopper of Fig. 3.15: (a) without snubber, (b) with snubber

47

Io

VCE,piC

0

Io ii

0 t0

vCE

(b)

Vi

t

VCE,p

0 t0

(a)

=

vCE

0

iC ii

t

Vi

Switching trajectories of the BJT chopper (a) without snubber, (b) with snubber

48

Vi

SOA

Io

iC

vCE0

0 VCE,p

VCE,p

(a)

0

Io

(b)

SOA

vCEVi

0

iC

Non-isolated drivers for a BJT: (a) single-transistor driver, (b) driver with a class B output stage

49

TR

BJT

TR

BJT

TR

TR

1

2

3

C

(a ) (b )

C

(+)

(+)

(-)

(-)

Anti-saturation Baker’s clamp for a BJT

50

D4

D0

D1 D2 D3

Baker’s Clamp Reduce the storage time of a

switching bipolar junction transistor (BJT) by applying a nonlinear negative feedback through various kinds of diodes.

Slow turn-off times of saturated BJTs is the stored charge in the base.

It must be removed before the transistor will turn off.

The diode-based Baker clamps prevent the transistor from saturating and thereby accumulating a lot of stored charge

51

Driver for a BJT with transformer isolation

52

(+)

( -)

BJT

T R

T R 1

2

P T R

Driver for a BJT with transformer isolation

53

(+ )

(+ ) (+ )

(+ )

BJT

(+ )

(-)

(a)

(b)

Bi

ON

OFF

t

Insulated-gate bipolar transistor

IGBT

54

55

Insulated-gate bipolar transistor

• Used as an electronic switch which, as it was developed, came to combine high efficiency and fast switching.

• The IGBT combines the simple gate-drive characteristics of MOSFETs with the high-current and low-saturation-voltage capability of bipolar transistors.

• Used in medium- to high-power applications like switched-mode power supplies, traction motor control, plasma physics and induction heating

IGBT(a) equivalent circuit(b) circuit symbol

56

C

E

G

C

G

I

VCE

C

E

Voltage-current characteristics of IGBT

57

IC

GE V

ON

OFF

VCE

58

TABLE 2.5 Example IGBTs

_____________________________________________________________________________

Symbol: 5SNA 2400E170100 5SNA 1500E330300 5SNA 0600G650100

(ABB) (ABB) (ABB)

VCE: 1.7 kV 3.3 kV 6.5 kV

IC: 2.4 kA 1.5 kA 0.6 kA

IFSM: 20 kA 14 kA 6 kA

VCE(sat): 2.6 V 3 V 5.4 V

IGES: 0.5 µA 0.5 µA 0.5 µA

tON: 0.32 µs 0.57 µs 0.57 µs

tOFF: 1.1 µs 1.68 µs 1.86 µs

Size: 190×140×38 mm 190×140×38 mm 190×140×48 mm

_____________________________________________________________________________

VCE(sat) – collector-emitter saturation voltage, IGES – gate leakage current

59

TABLE 2.4 Example High-Power MOSFETs

______________________________________________________________________________

Symbol: VMO 650-01F IXFB 100N50P APT45M100J STP4N150

(IXYS) (IXYS) (Microsemi) (STMicroel,)

VDSS: 100 V 500 V 1000 V 1500 V

ID: 690 A 100 A 45 A 4 A

VGS: 20 V 30 V 30 V 30 V

IGS: 0.5 µA 0.2 µA 0.1 µA 0.1 µA

RDS: 1.8 mΩ 49 mΩ 170 mΩ 5 Ω

tON: 500 ns 36 ns 85 ns 35 ns

tOFF: 800 µs 110 ns 285 ns 45 ns

Size: 110×62×30 mm 26×20×5 mm 38×25×12 mm 16×10×5 mm

______________________________________________________________________________

RDS – static drain-source on resistance, IGS – gate leakage current

Metal oxide semiconductor field-effect transistor

MOSFET

60

Power MOSFET: (a) semiconductor structure, (b) circuit symbol

61

n

p

n

(a) (b)

S O U R C E

D R AIN

G A TE

O X ID E

M E T A L

D

G

S

VD S

ID

Voltage-current characteristics of power MOSFET

62

CONSTANT RESISTANCE LINES ON

OFF VDS

ID

VGS

Driver for a power MOSFET with transformer isolation

63

MOSFET

PTR

AM

D

Driver for a power MOSFET with optical isolation

64

( -)

(+ ) (+ )

AMP L

M O S F E T

( -)

(+ )

(+ )

(-)

Gate drive for a power MOSFET with a high-current TTL clock driver

65

MOSFET

CD

(+)

Snubbers for: (a) power diode, (b) SCR

66

(a )

(b )

GTO - Gate Turn-Off Thyristor - with turn-on and turn-off snubbers

67

TUR N -O F FS N U B B E R

TUR N -O NS N U B B E R

i

i

i

v

Combined on-and-off snubber for a transistor

68

ii

iC

v CE

Snubber for transistors in bridge converters: (a) RC, (b) RCD, (c) charge and discharge RCD, (d) discharge-suppressing RCD

69

(a) (b)

(c) (d)

Turn-off capacitive snubber with passive energy recovery

70

Turn-off capacitive snubber for a GTO with active energy recovery

71

72

TABLE 3.1 Comparison of Thermal and Electrical Quantities

______________________________________________________________________________

Thermal Quantity Electrical Quantity ______________________________________________________________________________

Amount of heat (energy), Q (J) Electric charge, Q (C)

Heat current (power), P (W) Electric current, I (A)

Temperature, Θ (oK) Electric voltage, V (V)

Thermal resistance, RΘ (oK/W) Electric resistance, R (Ω)

Thermal capacity, CΘ (J/ oK) Electric capacitance, C (F)

Thermal time constant, 𝜏Θ = 𝑅Θ𝐶Θ (s) Electrical time constant, 𝜏= 𝑅𝐶 (s)

______________________________________________________________________________

Power diode with a heat sink: (a) physical arrangement, (b) thermal

equivalent circuit

73

HEAT SINK

CAB LE

SEM ICO NDU CTOR

O

R S A

OR C S

OR J C

OC S

OC C

OC J

O J

O A

(a) (b)

CASE WAF ER

P

O C

O S

l

Block diagram of an adjustable-speed ac drive

74

MO TO RIN VE R TE R

C O N TR O LLE RD S P

S Y S TE M

RE FE RE NC ES PE E D S IGNA L

C URRE NT S IGNA LS

C URRE NTS ENS ORS

S PE E D S E NS OR

REF ERE NC E C URRENT SIGNALS

S PE E D S IGNA L

(+ )

( - )

C R A

C R

C R

B

C

LOAD