AN1008
8
Explanation of Maximum Ratings and
Characteristics for Thyristors
VDRM: Peak Repetitive Forward (Off-state) Voltage
Introduction
SCR
Data sheets for SCRs and triacs give vital information regarding
maximum ratings and characteristics of thyristors. If the maxi-
mum ratings of the thyristors are surpassed, possible irrevers-
ible damage may occur. The characteristics describe various
pertinent device parameters which are guaranteed as either min-
imums or maximums. Some of these characteristics relate to the
ratings but are not ratings in themselves. The characteristic does
not define what the circuit must provide or be restricted to, but
defines the device characteristic. For example, a minimum value
is indicated for the dv/dt because this value depicts the guaran-
teed worst-case limit for all devices of the specific type. This min-
imum dv/dt value represents the maximum limit that the circuit
should allow.
The peak repetitive forward (off-state) voltage rating (Figure
AN1008.1) refers to the maximum peak forward voltage which
may be applied continuously to the main terminals (anode, cath-
ode) of an SCR. This rating represents the maximum voltage the
SCR should be required to block in the forward direction. The
SCR may or may not go into conduction at voltages above the
V
DRM rating. This rating is specified for an open-gate condition
and gate resistance termination. A positive gate bias should be
avoided since it will reduce the forward-voltage blocking capabil-
ity. The peak repetitive forward (off-state) voltage rating applies
for case temperatures up to the maximum rated junction temper-
ature.
Triac
Maximum Ratings
The peak repetitive off-state voltage rating should not be sur-
passed on a typical, non-transient, working basis. (Figure
AN1008.2) VDRM should not be exceeded even instantaneously.
This rating applies for either positive or negative bias on main
terminal 2 at the rated junction temperature. This voltage is less
than the minimum breakover voltage so that breakover will not
occur during operation. Leakage current is controlled at this volt-
age so that the temperature rise due to leakage power does not
contribute significantly to the total temperature rise at rated cur-
rent.
VRRM: Peak Repetitive Reverse Voltage — SCR
The peak repetitive reverse voltage rating is the maximum peak
reverse voltage that may be continuously applied to the main ter-
minals (anode, cathode) of an SCR. (Figure AN1008.1) An open-
gate condition and gate resistance termination is designated for
this rating. An increased reverse leakage can result due to a pos-
itive gate bias during the reverse voltage exposure time of the
SCR. The repetitive peak reverse voltage rating relates to case
temperatures up to the maximum rated junction temperature.
+I
+I
Voltage Drop (V ) at
T
Specified Current (i )
T
Voltage Drop (VT) at
Specified Current (iT)
Latching Current (I )
L
Latching Current (IL)
Off-state Leakage
Current – (I
Specified V
) at
DRM
DRM
Off - State Leakage
Current - (IDRM) at
Specified VDRM
Minimum Holding
Reverse Leakage
Current - (IRRM) at
Specified VRRM
Current (I
)
H
Minimum Holding
Current (IH
-V
+V
)
-V
+V
Specified Minimum
Off-state
Blocking
Specified Minimum
Off - State
Specified Minimum
Reverse Blocking
Blocking
Voltage (V
)
DRM
Voltage (VRRM
)
Voltage (VDRM
)
Breakover
Voltage
Reverse
Breakdown
Voltage
Forward
Breakover
Voltage
-I
-I
Figure AN1008.2
V-I Characteristics of Triac Device
Figure AN1008.1
V-I Characteristics of SCR Device
©2002 Teccor Electronics
Thyristor Product Catalog
AN1008 - 1
http://www.teccor.com
+1 972-580-7777
TECCOR [ TECCOR ELECTRONICS ]
