how does a silicon controlled rectifier work?

Question

how it goes frm off to on state

Answer 1

its work when anode voltage is grater that breakdownvolt(only when grid volt is zero)

Answer 2

The SCR does not pass current unless there is a trigger voltage present. It has 3 leads, like a transistor. Unlike a transistor, once triggered, current will continue to pass even if the trigger voltage is removed. When used in DC circuits, like a crow-bar, the incoming voltage has to be removed, for example by blowing a fuse. In AC circuits, the reverse polarity cycle can be used to shut off the current flow.

Answer 3

take 2 transistors one npn the other pnp

emitter of pnp to plus rail
emitter of npn to ground

connect base of one to collector of other
and the remaining base to the remaining unused collector

add base emitter resistors to take away leakage

and the arrangement stays off

unless the dv/dt is large
or a trigger is applied

then both transistors come on (shorting the rails)


a lot of integrated circuits have (unwanted) scr's
where NPNP junctions are formed

Answer 4

Look at: http://en.wikipedia.org/wiki/Thyristor

Answer 5

have you pressed the 'on' button?

no idea to be honest mate