AN1001
Application Notes
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AN1001 - 4
2002 Teccor Electronics
Thyristor Product Catalog
Electrical Characteristic Curves of Thyristors
Figure AN1001.12
V-I Characteristics of SCR Device
Figure AN1001.13
V-I Characteristics of Triac Device
Figure AN1001.14
V-I Characteristics of Bilateral Trigger Diac
Figure AN1001.15
V-I Characteristics of a Sidac Chip
Methods of Switching on Thyristors
Three general methods are available for switching thyristors to
on-state condition:
Application of gate signal
Static dv/dt turn-on
Voltage breakover turn-on
Gate signal must exceed I
and V
requirements of the thyristor
used. For an SCR (unilateral device), this signal must be positive
with respect to the cathode polarity. A triac (bilateral device) can
be turned on with gate signal of either polarity; however, different
polarities have different requirements of I
GT
and V
GT
which must
be satisfied. Since diacs and sidacs do not have a gate, this
method of turn-on is not applicable. In fact, the single major
application of diacs is to switch on triacs.
Static dv/dt Turn-on
Static dv/dt turn-on comes from a fast-rising voltage applied
across the anode and cathode terminals of an SCR or the main
terminals of a triac. Due to the nature of thyristor construction, a
small junction capacitor is formed across each PN junction.
Figure AN1001.16 shows how typical internal capacitors are
linked in gated thyristors.
Figure AN1001.16
Internal Capacitors Linked in Gated Thyristors
Reverse
Breakdown
Voltage
Forward
Breakover
Voltage
Specified Minimum
Off - State
Blocking
Voltage (V
DRM
)
+I
-I
+V
-V
Minimum Holding
Current (I
H
)
Voltage Drop (V
) at
Specified Current (i
T
)
Latching Current (I
L
)
Off - State Leakage
Current - (I
DRM
) at
Specified V
DRM
Specified Minimum
Reverse Blocking
Voltage (V
RRM
)
Reverse Leakage
Current - (I
RRM
) at
Specified V
RRM
Breakover
Voltage
Specified Minimum
Off-state
Blocking
Voltage (V
DRM
)
+I
-I
+V
-V
Minimum Holding
Current (I
H
)
Voltage Drop (V
) at
Specified Current (i
T
)
Latching Current (I
L
)
Off-state Leakage
Current – (I
DRM)
at
Specified V
DRM
+I
-I
10 mA
+V
-V
Breakover
Current
I
BO
Breakover
Voltage
V
BO
V
-V
+I
V
DRM
+V
V
S
I
S
I
H
R
S
I
DRM
I
BO
V
BO
V
T
I
T
(I
S
- I
BO
)
(V
BO
- V
S
)
R
S =
-I