Download Electronics

Electronics
- lectures for Mechanical Engineering
part 6
Dr. Bogusław Boratyński
Faculty of Microsystems Electronics and Photonics,
Wroclaw University of Technology,
2011
From the course syllabus
Basic literature & figure sources:
G. Rizzoni, Fundamentals of Electrical Engineering, McGraw-Hill
R.F. Pierret, Semiconductor Device Fundamentals, Addison-Wesley Publ.,
B.G. Streetman, Solid State Electronic Devices, Prentice-Hall,
J. Millman, Microelectronics, McGraw-Hill
Additional literature:
W. Marciniak, Przyrządy półprzewodnikowe i układy scalone, WNT,
A. Świt, J. Pułtorak, Przyrządy półprzewodnikowe, WNT,
B.G. Streetman, Przyrządy półprzewodnikowe, WNT
Power switches
DC and AC power switching
DC switches:
Bipolar transistor
MOSFET
IGBT
AC switching devices:
Thyristor
TRIAC
DIAC
MOSFET or bipolar transistor current switch
Input control signal UG = UGS
Input control signal: UI = UBE or II=IB
Result: rise of output current iD = iload
Result: rise of output current IC =Iload
IC
VDD , UCC - DC supply
load, RL
UCC
IB
U0 =UCE
UI =UBE
Switching circuit requirements:
- short switching times (μs).
- small ON state voltage:
UCEon, UDSon,
since power dissipated in transistor
while in ON state is:
P = IDon UDSon or P = ICon UCEon
UCE
UCEon
MOSFET switch
Change of the ON-time (duty cycle) allows
control of the power delivered to the load
- constant input voltage amplitude, typically UGS = 5V, 10V
- variable input voltage pulse duration
MOSFET transfer characteristic, ID – UGS
PWM - pulse-width modulation method
Common Source config.
Source: G . Rizzoni, Fundamentals of Electrical Engineering, McGraw-Hill
MOSFET switch (common drain)
Linear transfer characteristic, ID - UGS
Common Drain config.
Source: G . Rizzoni, Fundamentals of Electrical Engineering, McGraw-Hill
Transistor as a controlled switch (a driver)
DC motor (M) driver
H-bridge circuit
Power
supply
S1, S2, S3, S4 – single transistors or transistor circuits
L298 dual H bridge motor driver
Source: Wikipedia
S1 S2 S3 S4
Result
1
0 0
1
Motor moves right
0
1 1
0
Motor moves left
0
0 0
0
Motor free runs
0
1 0
1
Motor brakes
1
0 1
0
Motor brakes
1
1 0
0
Short Power Supply
0
0 1
1
Short Power Supply
1
1 1
1
Short Power Supply
variation – „half-H”
(two transistors only)
push-pull configuration
IGBT switching device
IGBT - Insulated Gate Bipolar Transistor
- takes advantage of MOSFET current-less input (voltage control)
and BJT high switching current capability
- low UCE in on-state
- very high switching voltages [kV]
- symbol
- equivalent circuit
IGBT switching device
IGBT Insulated Gate Bipolar Transistor
=
- application circuit
Power line
supply voltage
uC – microcontroller, triggering cct.
Source: Wikipedia
Thyristor – ac power switch (dc characteristics)
DC biasing circuit: UGK >0, UAK >0
pulse of IG to switch-on (to trigger)
DC I-V characteristics
conducting
RL
A
G
UAK
IG
blocking
K
reverse
UGK
Thyristor
SCR – Silicon Controlled Rectifier
Source: J. Millman, Microelectronics, McGraw-Hill
Thyristor – operation principle
Thyristor
SCR – Silicon Controlled Rectifier
”Diode” current controlled
by the gate current pulse
p-n-p-n structure,
3 p-n junctions in series
conducting
switching
Main current – IAK = Iload [A] [kA]
Control current pulse – IG [mA]
blocking
reverse
Source: J. Millman, Microelectronics, McGraw-Hill
Triggering methods:
1. Pulse of the gate current IG
2. Rise of VAK > VBF
3. Light pulse – light triggered thyristors, triacs
Thyristor – circuit application - ac current switch
Basic application system example:
control of light intensity / light dimmer
(heating systems, electrical motors) LOAD
A
DIODE
pow er line
230V
SCR
K
lighting
system
current & voltage waveforms
Uinput
IG pulse
G
gate contol
circuit
ωt
IG
IAK
DIAC or DIODE
Iload
ωt
UAK
IG
ωt
Thyristor – circuit application - ac current switch
Basic application system example:
control of light intensity / light dimmer
(heating systems, electrical motors) LOAD
A
lighting
system
K
current & voltage waveforms
Uinput
IG pulse
G
gate contol
circuit
ωt
IG
pow er line
230V
IAK
Iload
ωt
A
K
LOAD
lighting
system
UAK
G
gate contol
circuit
pow er line
230V
ωt
TRIAC – operation principle, dc I-V characteristic
TRIAC – bidirectional thyristor - symmetrical I-V characteristic
(equivalent of two thyristors connected antiparallel)
IG pulse turns-on the triac,
also light-triggered triacs
A1
IG pulse
conducting
G
IG pulse
blocking
blocking
A2
conducting
Application in low and medium power circuits
TRIAC – operation principle - ac current switch
TRIAC – typical application circuit
A1 positive
Uinput
IG pulse
A1
ωt
A1 negative
IG pulse
ac power
supply
Uinput
G
IAK
Iload
ωt
UAK
Load
A2
ωt
DIAC – operation principle
DIAC – two terminal (no gate) switching device - symmetrical I-V characteristic
switching method – voltage rise above threshold, Vth= 40V ÷ 60V
A2
Vth
Vth
Source J. Millman, Microelectronics, McGraw-Hill