Hi there,
I was hoping for an answer to a problem I have.

So basically I want to use Mosfets as a switch. The only problem I have is that it needs to be independent of the direction of the current (like a relais).

So as far as I know Mosfets can only be used in DC application since the voltage potential on the Drain needs to be higher than at the gate.
Since It is not a fast switching AC Power source (It's basically DC current but the polarity changes from time to time) I also can't use a TRIAC as far as I'm concerned.

So my idea was to use two commonly used Mosfet switching circuits and connect them in parallel but one is the other way around (Gate from Mosfet 1 connected to source of Mosfet2 and vice versa) so that each Mosfet is responsible for one polarity and thus there will always be one Mosfet where the Gate voltage is lower than at the Drain and one where it's higher and therefore not “open”. Do I need some Diodes on top of that or not.


Is my thinking correct or does such a circuit even work or does someone have a better idea or is there even a different component that I'm unaware of.



Thanks for every response. Hopefully my explanation was clear if not just ask

 

Why cant you use a Triac,, or two Thyristors back to back?

 

Put a bridge rectifier around the MOSFET

 

Why cant you use a Triac,, or two Thyristors back to back?

A TRIAC would latch on until the polarity reversed. So if the TS wants to be able to interrupt circuit before polarity reversal, TRIAC won't work.

 

A TRIAC would latch on until the polarity reversed. So if the TS wants to be able to interrupt circuit before polarity reversal, TRIAC won't work.

I know that. I want to know what the TS is doing...

 

If the frequency is low (50/60 Hz) you could drive two NFETS with these crazy things...

Connect them in series, but use two driver chips.
The body diode of one will always conduct anyway, but turning both FETS on will reduce the forward voltage of the whole thing.

https://www.vishay.com/docs/83469/vom1271t.pdf

 

Classic SSR -

https://www.electronics-tutorials.ws/power/solid-state-relay.html


Regards, Dana.

 

See