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Thyristor
Elektronika(TKE 4012)
Eka Maulana
maulana.lecture.ub.ac.id
Thyristor
• Thyristor: devais semikonduktor solid state
empat layer dari bahan type-n dan type-p
yang berfungsi sebagai Saklar Elektronik
• Jenis: SCR, DIAC, TRIAC
photothyristor
This latch is stable in either of two states.
Latch On state Off state
Q1
Q2
Q1
Q2
p
p
n
n
{Q1
The four-layer diode
{Q2
Four-layer diode breakover
I
VIH
VK VB
The silicon controlled rectifier (SCR)
Q1
Q2
Anode
Gate
Cathode
p
p
n
n
Anode
Gate
Cathode
Anode
Gate
Cathode
SCRs
• The most widely used thyristors
• Use gate triggering for turn-on instead of
breakover triggering
• Data sheets list the gate trigger voltage
(VGT) and the gate trigger current (IGT)
• Turn-off requires reducing the current to
less than the holding current (IH)
Load
+VAA
A B C D
A B C D
+VAA
An SCR does not turn off at the end of the trigger pulse.
Power
supply
Protected
load
SCR crowbar to protect a load from overvoltage
The overvoltage that triggers the crowbar: VT = VZ + VGT
VT
VZ
VGT
Power
supply
Protected
load
Adding gain to a crowbar circuit
R2
R1
R4
R3
R1 is the trigger adjust
Power
supply
Protected
load
Adding an IC amplifier to a crowbar circuit
10 kW
10 kW 10 kW
IC
VZ
A
The circuit triggers when VA exceeds VZ.
VA
Load
120 V
SCR phase control
qconduction
vline
vload
qfire
R1
R2C
Load
R1
R2C
RC snubber
A snubber network can be used to limit
the rate of voltage rise across the SCR.
Bidirectional thyristors can conduct in either direction.
Four-layer diodes
in reverse parallel
Diac
I
SCRs in
reverse parallel
Triac
IGate
The triac is a popular bidirectional thyristor.
Load
120 V
Triac phase control
vline
vload
R1
R2C
Protected
load
Triac crowbar
R2
R1
R3
R2 is the trigger adjust
120 V
Fuse
Triac
Diac
Sensitivity
adjust
RL RL
The photo-SCR is
triggered by light.
Maximum
sensitivity
Open
gate
A B C D
A B C D
RL
RG
The gate-controlled switch is turned
off with a reverse-biased trigger.
The silicon-controlled switch is
a low-current device.
Cathode
gate
Anode
Anode
gate
Cathode
Either gate can be used to trigger or open this device.
Unijunction transistor (UJT)
n
p V
vin
E
B2
B1
RE
When vin reaches the standoff voltage, the resistance
between the emitter and B1 drops dramatically.
E
B2
B1
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