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POWER ELECTRONICS Devices, Circuits, and Applications FOURTH EDITION
CHAPTER CHAPTER
9
Thyristors
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Learning Outcomes
After completing this chapter, students should be able to do the following: List the different types of thyristors. Describe the turn-on and turn-off characteristics of thyristors. Describe the two-transistor model of thyristors. Explain the limitations of thyristors as switches. Describe the gate characteristics and control requirements of different types of thyristors and their models. Apply the thyristor SPICE models.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Symbols and Their Meanings
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.1
Thyristor symbol and three pn-junctions.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.2
Cross section of a thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.3
Thyristor circuit and ν–i characteristics.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.4
Two-transistor model of thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.2 and 9.3
Two-transistor Model of Thyristor
• For transistor Q1, the emitter current is
the anode current IA, and the collector current IC1 can be found from Eq. (9.1):
• For transistor Q2, the collector current IC2
is
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.4 and 9.5
Two-transistor Model of Thyristor
• By combining IC1 and IC2, we get
• For a gating current of IG, IK = IA + IG and
solving Eq. (9.4) for IA gives
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.5
Typical variation of current gain with emitter current.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.6
Two-transistor transient model of thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equation 9.6
Two-transistor Transient Model of Thyristor
• The current through capacitor Cj2 can be
expressed as
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.7
Effects of gate current on forward blocking voltage.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.8
Turn-on characteristics.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.9
Turn-off characteristics.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.10
Amplifying gate thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.11
Bidirectional phase-controlled thyristor. [Ref. 5]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.12
Fast-switching thyristors. (Courtesy of Powerex, Inc.)
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.13
Characteristics of a TRIAC.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.14
Reverse-conducting thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.15
Gate turn-off (GTO) thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.16
Typical GTO turn-on and turn-off pulses. [Ref. 8]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.17
A GTO turn-off curcuit. [Ref. 8]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.18
A 200-V, 160-A GTO. (Image courtesy of Vishay Intertechnology, Inc.)
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.19
Junctions of 160-A GTO in Figure 9.18. (Image courtesy of Vishay Intertechnology, Inc.)
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.20
Schematic cross section of the SiC GTO thyristor [59].
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.21
FET-controlled thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.22
MOS turn-off (MTO) thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.23
Emitter turn-off (ETO) thyristor. [Ref. 22, Y. Li]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.24
p-type SiC ETO [62]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.25
Cross section of IGCT with a reverse diode.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.26
Schematic and equivalent circuit for p-channel MCTs.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.27
Cross section and equivalent circuit of a SITH. [Ref. 49, J. Wang]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Table 9.1
Comparisons of Different Thyristors
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Table 9.1 (continued)
Comparisons of Different Thyristors
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Table 9.1 (continued)
Comparisons of Different Thyristors
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Table 9.1 (continued)
Comparisons of Different Thyristors
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Table 9.1 (continued)
Comparisons of Different Thyristors
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.28
Thyristor current waveform.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.29
Off-state characteristics of two thyristors.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.30
Three series-connected thyristors.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.31
Forward leakage currents with equal voltage sharing.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.32
Reverse recovery time and voltage sharing.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.11 and 9.12
Reverse Recovery Time and Voltage Sharing
• Substituting Eq. (9.10) into Eq. (9.8)
yields
• The worst-case transient voltage sharing
that occurs when Q1 = 0 and ΔQ = Q2 is
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equation 9.13
Reverse Recovery Time and Voltage Sharing
• A derating factor that is normally used to
increase the reliability of the string is defined as
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.33
Current sharing of thyristors.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.34
Thyristor switching circuit with di/dt limiting inductors.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equation 9.14
di/dt limiting inductors
• The forward di/dt is
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.35
dv/dt protection circuits.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.15 and 9.16
dv/dt protection circuits
• The circuit dv/dt can be found
approximately from
• The value of Rs is found from the
discharge current ITD.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.17 and 9.18
dv/dt protection circuits
• The dv/dt is limited by R1 and Cs. (R1 +
R2) limits the discharging current such that
• From Eqs. (2.40) and (2.41), the
damping ratio δ of a second-order equation is
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.36
SPICE thyristor model.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.37
Complete proposed silicon-controlled rectifier model. [Ref. 4, F. Gracia]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.38
Four-transistor GTO model. [Ref. 12, M. El-Amia]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.39
MCT model. [Ref. 37, S. Yuvarajan]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.40
Cross section of DIAC and its symbols.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.41
ν–i characteristics of DIACs.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.42
Voltage and current waveforms of a DIAC circuit.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.43
DIAC for triggering a TRIAC.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.44
Photo-SCR coupled isolator.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.45
Pulse transformer isolation.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.46
Gate protection circuits.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.47
UJT triggering circuit.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.23 and 9.24
Unijunction Transistor
• The period of oscillation, T, is fairly
independent of the dc supply voltage Vs, and is given by
• If the load line fails to pass to the right of
the peak point, the UJT cannot turn on. This condition can be satisfied if
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.25 and 9.26
Unijunction Transistor
• At the valley point IE = IV and VE = Vv so
that the condition for the lower limit on R to ensure turning off is
• Vp is given by
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.27 and 9.28
Unijunction Transistor
• The width tg of triggering pulse is
• Resistor RB2 has a value of 100 Ω or
greater and can be determined approximately from
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.48
PUT triggering circuit.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.29 and 9.30
Programmable Unijunction Transistor
• Vp is given by
• which gives the intrinsic ratio as
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equation 9.31
Programmable Unijunction Transistor
• The period of oscillation T is given
approximately by
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.33 and 9.34
Programmable Unijunction Transistor
• RG = R1 R2/(R1 + R2). R1 and R2 can be
found from
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
CHAPTER CHAPTER
9
Thyristors
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Learning Outcomes
After completing this chapter, students should be able to do the following: List the different types of thyristors. Describe the turn-on and turn-off characteristics of thyristors. Describe the two-transistor model of thyristors. Explain the limitations of thyristors as switches. Describe the gate characteristics and control requirements of different types of thyristors and their models. Apply the thyristor SPICE models.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Symbols and Their Meanings
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.1
Thyristor symbol and three pn-junctions.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.2
Cross section of a thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.3
Thyristor circuit and ν–i characteristics.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.4
Two-transistor model of thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.2 and 9.3
Two-transistor Model of Thyristor
• For transistor Q1, the emitter current is
the anode current IA, and the collector current IC1 can be found from Eq. (9.1):
• For transistor Q2, the collector current IC2
is
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.4 and 9.5
Two-transistor Model of Thyristor
• By combining IC1 and IC2, we get
• For a gating current of IG, IK = IA + IG and
solving Eq. (9.4) for IA gives
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.5
Typical variation of current gain with emitter current.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.6
Two-transistor transient model of thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equation 9.6
Two-transistor Transient Model of Thyristor
• The current through capacitor Cj2 can be
expressed as
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.7
Effects of gate current on forward blocking voltage.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.8
Turn-on characteristics.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.9
Turn-off characteristics.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.10
Amplifying gate thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.11
Bidirectional phase-controlled thyristor. [Ref. 5]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.12
Fast-switching thyristors. (Courtesy of Powerex, Inc.)
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.13
Characteristics of a TRIAC.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.14
Reverse-conducting thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.15
Gate turn-off (GTO) thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.16
Typical GTO turn-on and turn-off pulses. [Ref. 8]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.17
A GTO turn-off curcuit. [Ref. 8]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.18
A 200-V, 160-A GTO. (Image courtesy of Vishay Intertechnology, Inc.)
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.19
Junctions of 160-A GTO in Figure 9.18. (Image courtesy of Vishay Intertechnology, Inc.)
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.20
Schematic cross section of the SiC GTO thyristor [59].
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.21
FET-controlled thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.22
MOS turn-off (MTO) thyristor.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.23
Emitter turn-off (ETO) thyristor. [Ref. 22, Y. Li]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.24
p-type SiC ETO [62]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.25
Cross section of IGCT with a reverse diode.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.26
Schematic and equivalent circuit for p-channel MCTs.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.27
Cross section and equivalent circuit of a SITH. [Ref. 49, J. Wang]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Table 9.1
Comparisons of Different Thyristors
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Table 9.1 (continued)
Comparisons of Different Thyristors
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Table 9.1 (continued)
Comparisons of Different Thyristors
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Table 9.1 (continued)
Comparisons of Different Thyristors
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Table 9.1 (continued)
Comparisons of Different Thyristors
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.28
Thyristor current waveform.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.29
Off-state characteristics of two thyristors.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.30
Three series-connected thyristors.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.31
Forward leakage currents with equal voltage sharing.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.32
Reverse recovery time and voltage sharing.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.11 and 9.12
Reverse Recovery Time and Voltage Sharing
• Substituting Eq. (9.10) into Eq. (9.8)
yields
• The worst-case transient voltage sharing
that occurs when Q1 = 0 and ΔQ = Q2 is
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equation 9.13
Reverse Recovery Time and Voltage Sharing
• A derating factor that is normally used to
increase the reliability of the string is defined as
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.33
Current sharing of thyristors.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.34
Thyristor switching circuit with di/dt limiting inductors.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equation 9.14
di/dt limiting inductors
• The forward di/dt is
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.35
dv/dt protection circuits.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.15 and 9.16
dv/dt protection circuits
• The circuit dv/dt can be found
approximately from
• The value of Rs is found from the
discharge current ITD.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.17 and 9.18
dv/dt protection circuits
• The dv/dt is limited by R1 and Cs. (R1 +
R2) limits the discharging current such that
• From Eqs. (2.40) and (2.41), the
damping ratio δ of a second-order equation is
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.36
SPICE thyristor model.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.37
Complete proposed silicon-controlled rectifier model. [Ref. 4, F. Gracia]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.38
Four-transistor GTO model. [Ref. 12, M. El-Amia]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.39
MCT model. [Ref. 37, S. Yuvarajan]
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.40
Cross section of DIAC and its symbols.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.41
ν–i characteristics of DIACs.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.42
Voltage and current waveforms of a DIAC circuit.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.43
DIAC for triggering a TRIAC.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.44
Photo-SCR coupled isolator.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.45
Pulse transformer isolation.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.46
Gate protection circuits.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.47
UJT triggering circuit.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.23 and 9.24
Unijunction Transistor
• The period of oscillation, T, is fairly
independent of the dc supply voltage Vs, and is given by
• If the load line fails to pass to the right of
the peak point, the UJT cannot turn on. This condition can be satisfied if
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.25 and 9.26
Unijunction Transistor
• At the valley point IE = IV and VE = Vv so
that the condition for the lower limit on R to ensure turning off is
• Vp is given by
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.27 and 9.28
Unijunction Transistor
• The width tg of triggering pulse is
• Resistor RB2 has a value of 100 Ω or
greater and can be determined approximately from
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Figure 9.48
PUT triggering circuit.
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.29 and 9.30
Programmable Unijunction Transistor
• Vp is given by
• which gives the intrinsic ratio as
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equation 9.31
Programmable Unijunction Transistor
• The period of oscillation T is given
approximately by
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
Equations 9.33 and 9.34
Programmable Unijunction Transistor
• RG = R1 R2/(R1 + R2). R1 and R2 can be
found from
Power Electronics: Devices, Circuits, and Applications, 4e Muhammad H. Rashid
Copyright ©2014 by Pearson Education, Inc. All rights reserved.
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