K0900E70 Datasheet, PDF (122/224 Pages) Teccor Electronics – Thyristor Product Catalog

AN1001
Application Notes
Triac
Basic Operation
Figure AN1001.4 shows the simple block construction of a triac.
Its primary function is to control power bilaterally in an AC circuit.
Main
Terminal 2
(MT2)
P
N
N
Block Construction
N
P
N
Main
Terminal 1
(MT1)
Gate
MT2
Gate
MT1
Schematic Symbol
Figure AN1001.4 Triac Block Construction
Operation of a triac can be related to two SCRs connected in par-
allel in opposite directions as shown in Figure AN1001.5.
Although the gates are shown separately for each SCR, a triac
has a single gate and can be triggered by either polarity.
MT1
MT2
Figure AN1001.5 SCRs Connected as a Triac
Since a triac operates in both directions, it behaves essentially
the same in either direction as an SCR would behave in the for-
ward direction (blocking or operating).
Geometric Construction
Figure AN1001.6 show simplified cross-sectional views of a triac
chip in various gating quadrants and blocking modes.
GATE(+)
IGT
N
MT1(-)
N
P
N
P
N
IT _MT2(+)
QUADRANT I
GATE(-)
IGT
N
MT1(-)
N
P
N
P
N
MT2(+)
QUADRANT II
MT1(-)
Blocking
Junction
MT2(+)
Equivalent Diode
Relationship
GATE(-)
IGT
N
MT1(+)
N
P
N
P
N
MT2(-)
IT
QUADRANT III
GATE(+)
IGT
N
MT1(+)
N
P
N
P
N
MT2(-) ^IT
QUADRANT IV
MT1(+)
Blocking
Junction
MT2(-)
Equivalent Diode
Relationship
Figure AN1001.6 Simplified Cross-sectional of Triac Chip
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AN1001 - 2
©2002 Teccor Electronics
Thyristor Product Catalog