Transcript SCR/Thyrisitor pnpn structure with 3 pn junctions

SCR/Thyrisitor
pnpn structure with 3 pn junctions
Cross-section of the pnpn structure
+
J1
J2
VAK
J3
-
IA = 0
Apply a forward bias voltage to the Anode-Cathode
Junctions J1 and J3 are forward biased
Junction J2 is reverse biased
Only a small amount of current flows from A to K
The device is in it’s OFF or “Forward Blocking” State
SCR/Thyristor (continued)
+
VAK
-
IA
Increase the Anode-Cathode voltage until
“breakdown” occurs. Anode current increases.
“Conducting state”
Thyristor Volt-Ampere Characteristic
Two-Transistor Model
Effects of Increasing Gate Current
Line-Commutated Thyristor Circuit
Forced-Commutated Thyristor Circuit
Triac – Bi-directional Thyristor
Triac Volt-Ampere Characteristic