Question about IGBTs (Insulated Gate Bipolar Transistor)

[phalanx]

Do IGBTs have an intrinsic diode like a normal BJT? I've never used them before and I need to switch a high powered resonant LC circuit and would like to avoid relays if at all possible. If they do, I suppose I could use a robust Triac or several in parallel to switch the circuit.

Thanks in advance
-Bill

 

[Styx]

err?

Are you talking abt in a BJT the base-emitter and base-collector form a PN junction thus are diodes (and hence why BJT's need a ~0.6V to bias them on).


If that is the case you would still need a free-wheel diode for the inductive load since that diode that is part of the BJT cannot provide a freewheel path for the collector inductive load

However you switch an inductor when current is still flowing (or possibly flowing) a freewheel path is NEEDED. Be your switch a relay,BJT,FET,IGBT or an old man throwing a contactor.

IGBT's are great use them (or if low power FET's). You will still need a diode across the inductor to provide a freewheel path.

If you were planning on using Triac's how were you going to switch them off once it is conducting?

 

[phalanx]

The system is in resonance so there will be an AC current flowing through the point that I need to switch. I just don't know if IGBTs share the intrinsic diode property of BJTs which would make it unsuitable for my application. Thats also why Triacs would work so long as they are robust enough to handle the power I might be driving through them. I want to avoid relays if possible but I will use them if necessary.

All I really need to know is if current will flow through a reversed biased IGBT.

Thanks again
-Bill

 

[Styx]

oh you mean: if you provide voltage emitter-collector (and not collector-emitter) then no it wont flow.

you gotta remember an IGBT is just a PNP trasistor with a N-type FET on its base

BUT!!!!
you have to be careful what IGBT you get since IGBT's are mainly used in inverters so freewheel diodes are needed, IGBT manu put a antiparralel diode in the package. There are lots-o- TO220 packages with no anti-parallel diode (as well as FETS)

just check the datasheet