Page 55 - Power Electronics Handbook

48 Power semiconductor devices

Gate @ Auxiliary thyristor
Cathode
Main
thyristor

(d)
Regenerative
Main Auxiliary Trigger source
cathode cathode Qate Regeneratbe

Anode
(e)

Anode current

Conducting
Conducting
region
region
rssiatance
rssiatance
(B) Anode (h)
Mpre 1.26 Thyristor configurations: (a) dice with bevelled edge; (b) shorted-emitter;
(c) interdigitated gate; (d) amplifying gate schematic; (e) amplifying gate structure;
(f) regenerative gate; (g) cell cross section showing effect of emitter lip resistance;
(h) effect of emitter lip resistance on the current-time characteristic

voltage is developed across it which opposes the gate signal. If the gate
voltage is low, it may even be reversed, as in Figure 1.26(h), which would
reduce the turn-on time still further.
In the regenerative gate arrangement of Figure 1.26(f) conduction is
commenced by a signal on the trigger gate, which is the only gate terminal
brought out of the package. Once anode-to-cathode current starts to flow it
causes a voltage drop across the emitter lip resistance. This is picked up by
the regenerative source and fed to the regenerative gate, which is usually
an interdigitated arrangement. The external circuit needs to provide only a