This document provides information about thyristors, which are the most important type of power semiconductor device. Thyristors have the highest power handling capability of semiconductor devices, with ratings up to 5000V/6000A and switching frequencies from 1-20kHz. Thyristors are inherently slow switching devices compared to other devices like BJTs and MOSFETs. Thyristors can be turned on by their gate but not turned off, making them useful as latching switches. The document discusses thyristor structure, operation, characteristics, types including phase control, fast switching, GTOs and TRIACs, and specifications like voltage and current ratings.
2. 2
ThyristorsThyristors
Most important type of powerMost important type of power
semiconductor device.semiconductor device.
Have the highest power handlingHave the highest power handling
capability.they have a rating of 5000V /capability.they have a rating of 5000V /
6000A with switching frequencies ranging6000A with switching frequencies ranging
from 1KHz to 20KHz.from 1KHz to 20KHz.
3. 3
Is inherently a slow switching deviceIs inherently a slow switching device
compared to BJT or MOSFET.compared to BJT or MOSFET.
Used as a latching switch that can beUsed as a latching switch that can be
turned on by the control terminal butturned on by the control terminal but
cannot be turned off by the gate.cannot be turned off by the gate.
5. 5
StructureStructure
}
}
}
}
G a t e C a t h o d e
J 3
J 2
J 1
A n o d e
1 0 c m
1 7 - 3
1 0 - 5 x 1 0 c m
1 3 1 4 - 3
1 0 c m
1 7 - 3
1 0 c m
1 9 - 3
1 0 c m
1 9 - 3
1 0 c m
1 9 - 3
n
+
n
+
p
-
n
–
p
p
+
1 0 mµ
3 0 - 1 0 0 mµ
5 0 - 1 0 0 0 mµ
3 0 - 5 0 mµ
9. 9
( )
( )
The general transistor equations are,
1
1
C B CBO
C E CBO
E C B
B E CBO
I I I
I I I
I I I
I I I
β β
α
α
= + +
= +
= +
= − −
10. 10
( ) ( )
1 1
1 1
1 1
1
1
Considering PNP transistor
of the equivalent circuit,
, , ,
,
1 1
E A C C
CBO CBO B B
B A CBO
I I I I
I I I I
I I I
α α
α
= = =
= =
∴ = − − − − −
11. 11
( ) ( )
2 2 2
2 2
2 2
2
2
Considering NPN transistor
of the equivalent circuit,
, ,
2
C C B B E K A G
C k CBO
C A G CBO
I I I I I I I I
I I I
I I I I
α
α
= = = = +
= +
= + + − − −
12. 12
( )
2 1
2 1 2
1 2
From the equivalent circuit,
we see that
1
C B
g CBO CBO
A
I I
I I I
I
α
α α
∴ =
+ +
⇒ =
− +
13. 13
( )
1 2
1 2
Case 1: When 0
1
g
CBO CBO
A
I
I I
I
α α
=
+
=
− +
( )
2 1 2
1 2
Case 2: When 0
1
G
g CBO CBO
A
I
I I I
I
α
α α
≠
+ +
=
− +
17. 17
Turn-offTurn-off
CharacteristiCharacteristi
cscs
A n o d e c u r r e n t
b e g in s t o
d e c r e a s e
t C
t q
t
t
C o m m u t a t io n
d i
d t
R e c o v e r y R e c o m b i n a t i o n
t 1
t 2 t 3 t 4 t 5
t r r t g r
t q
t c
V A K
I A
t q = d e v i c e o f f t im e
t c = c ir c u it o f f t im e
31. PHASE-CONTROL THYRISTORS : primarily for rectifying linePHASE-CONTROL THYRISTORS : primarily for rectifying line
frequency voltage and currents (phase controlled AC and DCfrequency voltage and currents (phase controlled AC and DC
motor drivers and high voltage power transmission). Averagemotor drivers and high voltage power transmission). Average
current 4000A, blocking voltage 5-7kV and on-state voltagecurrent 4000A, blocking voltage 5-7kV and on-state voltage
1.5-3V1.5-3V
INVERTER-GRADE THYRISTORS: small turn-off times (fromINVERTER-GRADE THYRISTORS: small turn-off times (from
a fewa few µµs to100s to100µµs depends on their blocking voltage and on-s depends on their blocking voltage and on-
state voltage drops), and small on-state voltage,state voltage drops), and small on-state voltage,
2500V-1500A.2500V-1500A.
LIGHT-ACTIVATED THYRISTORS: triggered by a pulse ofLIGHT-ACTIVATED THYRISTORS: triggered by a pulse of
light guided by optical fibers to a sensitive region, usedlight guided by optical fibers to a sensitive region, used
primarily in high voltage application such as high voltageprimarily in high voltage application such as high voltage
power transmission 4kV-3kApower transmission 4kV-3kA
32. DevicesDevices
SITH = Static Induction ThyristorSITH = Static Induction Thyristor
GTO = Gate Turn Off ThyristorGTO = Gate Turn Off Thyristor
MOS = Metal Oxide SemiconductorMOS = Metal Oxide Semiconductor
MCT = MOS Controlled ThyristorMCT = MOS Controlled Thyristor
MTO = MOS Turn Off ThyristorMTO = MOS Turn Off Thyristor
ETO = Emitter Turn Off ThyristorETO = Emitter Turn Off Thyristor
IGCT = Insulated Gate Controlled ThyristorIGCT = Insulated Gate Controlled Thyristor
TRIAC = Triode ThyristorTRIAC = Triode Thyristor
LASCR = Light Activated SCRLASCR = Light Activated SCR
38. 38
Phase Control ThyristorPhase Control Thyristor
These are converter thyristors.These are converter thyristors.
The turn-off time tThe turn-off time tqq is in the order of 50 tois in the order of 50 to
100100µµsec.sec.
Used for low switching frequency.Used for low switching frequency.
Commutation is natural commutationCommutation is natural commutation
On state voltage drop is 1.15V for a 600VOn state voltage drop is 1.15V for a 600V
device.device.
39. 39
They use amplifying gate thyristor.They use amplifying gate thyristor.
40. 40
Fast SwitchingFast Switching
ThyristorsThyristors
Also called inverter thyristors.Also called inverter thyristors.
Used for high speed switchingUsed for high speed switching
applications.applications.
Turn-off time tTurn-off time tqq in the range of 5 to 50in the range of 5 to 50µµsec.sec.
On-state voltage drop of typically 1.7V forOn-state voltage drop of typically 1.7V for
2200A, 1800V thyristor.2200A, 1800V thyristor.
High dv/dt and high di/dt rating.High dv/dt and high di/dt rating.
43. 43
Gate Turn-off ThyristorsGate Turn-off Thyristors
Turned on by applying positive gateTurned on by applying positive gate
signal.signal.
Turned off by applying negative gateTurned off by applying negative gate
signal.signal.
On state voltage is 3.4V for 550A, 1200VOn state voltage is 3.4V for 550A, 1200V
GTO.GTO.
Controllable peak on-state current IControllable peak on-state current ITGQTGQ isis
the peak value of on-state current whichthe peak value of on-state current which
can be turned-off by gate control.can be turned-off by gate control.
44. Gate-Turn-Off Thyristors (GTO)
• Slow switching speeds
• Used at very high power levels
• Require elaborate gate control circuitry
46. 46
Advantages over SCRsAdvantages over SCRs
Elimination of commutating components.Elimination of commutating components.
Reduction in acoustic & electromagneticReduction in acoustic & electromagnetic
noise due to elimination of chokes.noise due to elimination of chokes.
Faster turn-off, therefore can be used forFaster turn-off, therefore can be used for
higher switching frequencies.higher switching frequencies.
Improved efficiency of converters.Improved efficiency of converters.
47. 47
Advantages over BJTsAdvantages over BJTs
Higher voltage blocking capabilities.Higher voltage blocking capabilities.
High on-state gain.High on-state gain.
High ratio of peak surge current toHigh ratio of peak surge current to
average current.average current.
A pulsed gate signal of short duration onlyA pulsed gate signal of short duration only
is required.is required.
48. 48
Disadvantages of GTOsDisadvantages of GTOs
On-state voltage drop is more.On-state voltage drop is more.
Due to multi cathode structure higher gateDue to multi cathode structure higher gate
current is required.current is required.
Gate drive circuit losses are more.Gate drive circuit losses are more.
Reverse blocking capability is less than itsReverse blocking capability is less than its
forward blocking capability.forward blocking capability.
50. 50
Anti-parallel diode connected across SCRAnti-parallel diode connected across SCR
on the same silicon chip.on the same silicon chip.
This diode clamps the reverse blockingThis diode clamps the reverse blocking
voltage to 1 or 2V.voltage to 1 or 2V.
RCT also called Asymmetrical ThyristorRCT also called Asymmetrical Thyristor
(ASCR).(ASCR).
Limited applications.Limited applications.
51. 51
Static Induction ThyristorsStatic Induction Thyristors
Turned-on by applying positive gateTurned-on by applying positive gate
voltage.voltage.
Turned-off by applying negative gateTurned-off by applying negative gate
voltage.voltage.
Minority carrier device.Minority carrier device.
Low on-state resistance & low voltageLow on-state resistance & low voltage
drop.drop.
Fast switching speeds & high dv/dt & highFast switching speeds & high dv/dt & high
di/dt capabilities.di/dt capabilities.
52. 52
Switching time in order of 1 to 6Switching time in order of 1 to 6 µµsec.sec.
The rating can go upto 2500V / 500A.The rating can go upto 2500V / 500A.
Process sensitive.Process sensitive.
53. 53
Light-Activated SiliconLight-Activated Silicon
Controlled RectifiersControlled Rectifiers
Turned-on by direct light radiation onTurned-on by direct light radiation on
silicon wafer.silicon wafer.
Gate structure is sensitive for triggeringGate structure is sensitive for triggering
from practical light sources.from practical light sources.
Used in high voltage and high currentUsed in high voltage and high current
applications. Example: HVDCapplications. Example: HVDC
transmission, Static reactive powertransmission, Static reactive power
compensation.compensation.
54. 54
Offers complete electrical isolationOffers complete electrical isolation
between light triggering source & powerbetween light triggering source & power
circuit.circuit.
Rating could be has high as 4KV / 1500A.Rating could be has high as 4KV / 1500A.
di/dt rating is 250A /di/dt rating is 250A / µµsec.sec.
dv/dt rating is 2000V /dv/dt rating is 2000V / µµsec.sec.
56. Bipolar Junction Transistors (BJT)
• Used commonly in the past
• Now used in specific applications
• Replaced by MOSFETs and IGBTs
57.
58. 58
FET ControlledFET Controlled
ThyristorsThyristors
Combines aCombines a
MOSFET & aMOSFET & a
thyristor in parallelthyristor in parallel
as shown.as shown.
High switchingHigh switching
speeds & high di/dtspeeds & high di/dt
& dv/dt.& dv/dt.
59. 59
Turned on like conventional thyristors.Turned on like conventional thyristors.
Cannot be turned off by gate control.Cannot be turned off by gate control.
Application of these are where opticalApplication of these are where optical
firing is to be used.firing is to be used.
60. 60
MOS-ControlledMOS-Controlled
ThyristorThyristor
New device that has becomeNew device that has become
commercially available.commercially available.
Basically a thyristor with two MOSFETsBasically a thyristor with two MOSFETs
built in the gate structure.built in the gate structure.
One MOSFET for turning ON the MCTOne MOSFET for turning ON the MCT
and the other to turn OFF the MCT.and the other to turn OFF the MCT.
64. 64
FeaturesFeatures
Low on-state losses & large currentLow on-state losses & large current
capabilities.capabilities.
Low switching losses.Low switching losses.
High switching speeds achieved due toHigh switching speeds achieved due to
fast turn-on & turn-off.fast turn-on & turn-off.
Low reverse blocking capability.Low reverse blocking capability.
65. 65
Gate controlled possible if current is lessGate controlled possible if current is less
than peak controllable current.than peak controllable current.
Gate pulse width not critical for smallerGate pulse width not critical for smaller
device currents.device currents.
Gate pulse width critical for turn-off forGate pulse width critical for turn-off for
larger currents.larger currents.
67. MOSFETs
• Easy to control by the gate
• Optimal for low-voltage operation at high switching frequencies
• On-state resistance a concern at higher voltage ratings
78. Advantages of IGBTAdvantages of IGBT
Combines the advantages of BJT & MOSFETCombines the advantages of BJT & MOSFET
High input impedance like MOSFETHigh input impedance like MOSFET
Voltage controlled device like MOSFETVoltage controlled device like MOSFET
Simple gate drive, Lower switching lossSimple gate drive, Lower switching loss
Low on state conduction power loss like BJTLow on state conduction power loss like BJT
Higher current capability & higher switchingHigher current capability & higher switching
speed than a BJT. ( Switching speed lower thanspeed than a BJT. ( Switching speed lower than
MOSFET)MOSFET)
78
Prof. M. Madhusudhan Rao, E&C Dept., MSRIT
79. Applications of IGBTApplications of IGBT
ac and dc motor controls.ac and dc motor controls.
General purpose inverters.General purpose inverters.
Uninterrupted Power Supply (UPS).Uninterrupted Power Supply (UPS).
Welding Equipments.Welding Equipments.
Numerical control, Cutting tools.Numerical control, Cutting tools.
Robotics & Induction heating.Robotics & Induction heating.
79
Prof. M. Madhusudhan Rao, E&C Dept., MSRIT