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