Why does a thyristor keep conducting after removing the gate current?

[brent1369]

i have seen several videos of thyristors but they never really explain the fundamentals
they just say that cause there is a current flowing in there it keeps being on
but why does a transistor then turn off when you remove gate voltage

 

[berkeman]

i have seen several videos of thyristors but they never really explain the fundamentals
they just say that cause there is a current flowing in there it keeps being on
but why does a transistor then turn off when you remove gate voltage

Have you learned about "SCR Latchup" yet? Are you familiar with this view of the thyristor equivalent circuit?

https://www.electronics-notes.com/images/thyristor-scr-equivalent-circuit-01.svg

https://en.wikipedia.org/wiki/Latch-up

 

[brent1369]

I understand it when you divide it in 2 transistors but not when its 1 whole thyristor

 

[brent1369]

Cause you can't remove contact with highest P and highest N of th 2
and also lowest N and lowest P of th 1

 

[berkeman]

Cause you can't remove contact with highest P and highest N of th 2
and also lowest N and lowest P of th 1

Sorry, I can't parse that. A thyristor is just a PNPN structure, which is basically the same as the two transistors connected in the stacked format that I showed previously.

https://www.theengineeringprojects.com/wp-content/uploads/2019/11/what-is-thyristor.jpg

 

[davenn]

Sorry, I can't parse that. A thyristor is just a PNPN structure, which is basically the same as the two transistors connected in the stacked format that I showed previously.

https://www.theengineeringprojects.com/wp-content/uploads/2019/11/what-is-thyristor.jpg

View attachment 261674

Thanks for the heads up

Gosh, in the 50 odd years of doing electronics, the thyristor is probably one of my least understood
component. Not having had any real need to use them, has lead to some ignorance of them.Dave