AC16DGM Teccor Electronics, AC16DGM Datasheet - Page 127

• Manufacturer Part Number: AC16DGM
• Manufacturer: Teccor Electronics

AN1002
Introduction
Gating, latching, and holding currents of thyristors are some of
the most important parameters. These parameters and their
interrelationship determine whether the SCRs and triacs will
function properly in various circuit applications.
This application note describes how the SCR and triac parame-
ters are related. This knowledge helps users select best operat-
ing modes for various circuit applications.
Gating of SCRs and Triacs
Three general methods are available to switch thyristors to
on-state condition:
•
•
•
This application note examines only the application of proper
gate signal. Gate signal must exceed the I
ments of the thyristor being used. I
minimum gate current required to switch a thyristor from the off
state to the on state. V
required to produce the gate trigger current.
SCRs (unilateral devices) require a positive gate signal with
respect to the cathode polarity. Figure AN1002.1 shows the cur-
rent flow in a cross-sectional view of the SCR chip.
Figure AN1002.1
In order for the SCR to latch on, the anode-to-cathode current (I
must exceed the latching current (I
on, the SCR remains on until it is turned off when anode-to-cath-
ode current drops below holding current (I
©2002 Teccor Electronics
Thyristor Product Catalog
Applying proper gate signal
Exceeding thyristor static dv/dt characteristics
Exceeding voltage breakover point
SCR Current Flow
(+)
Gate
GT
P
Gating, Latching, and Holding of SCRs and Triacs
(gate trigger voltage) is the voltage
I
GT
Anode
P
N
(+) I
Cathode
GT
L
) requirement. Once latched
T
(gate trigger current) is the
N
(-)
H
GT
) requirement.
and V
GT
require-
AN1002 - 1
T
)
Triacs (bilateral devices) can be gated on with a gate signal of
either polarity with respect to the MT1 terminal; however, differ-
ent polarities have different requirements of I
Figure AN1002.2 illustrates current flow through the triac chip in
various gating modes.
Figure AN1002.2
QUADRANT III
QUADRANT IV
QUADRANT I
QUADRANT II
Triac Current Flow (Four Operating Modes)
Gate(+)
I
I
GT
GT
Gate(-)
Gate(-)
I
Gate(+)
I
GT
GT
AN1002
N
N
N
N
P
P
I T
MT2(-)
P
P
MT2(-)
MT2(+)
MT2(+)
N
N
N
N
N
MT1(-)
N
MT1(-)
N
MT1(+)
MT1(+)
N
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GT
P
P
N
N
P
P
and V
N
N
I
I
T
T
[phone]
GT
.