Good Day,
I have to calculate the Conduction losses of SiC MOSFET and how I am calculating total losses is by segregating the losses into three categories includes, Forward Conduction loss of MOSFET, Reverse Conduction Loss of MOSFET and Body Diode Reverse Conduction Losses. I am unable to understand the phenomenon of reverse conduction operation of MOSFET. Can anyone please explain or refer some good literature considering me as an beginner with very basic knowledge.
Thanks

 

Welcome to AAC.

Homework help has special rules on AAC and so is restricted to the Homework Help forum. I have moved your post.

Members can help you with your attempts to solve the problem based on what you have done, but they will not be able to provide unique solutions. Sometimes you will get broad hints about where to look.

Again, welcome. Glad you joined us.

 

I am unable to understand the phenomenon of reverse conduction operation of MOSFET.

In general a MOSFET will conduct equally well in both directions when biased on.
Under those conditions, the source and drain are interchangeable.
The difference is that, when off, there is a parasitic substrate diode from drain to source, that limits which direction the MOSFET can block voltage.

 

I am unable to understand the phenomenon of reverse conduction operation of MOSFET.

If the gate is off the reverse conduction is the same as the body diode. You need to know the current and the forward voltage of the diode.

 

If the gate is off the reverse conduction is the same as the body diode. You need to know the current and the forward voltage of the diode.

Does channel resistance between Drain to source remains same as forward conduction during reverse conduction?

 

In general a MOSFET will conduct equally well in both directions when biased on.
Under those conditions, the source and drain are interchangeable.
The difference is that, when off, there is a parasitic substrate diode from drain to source, that limits which direction the MOSFET can block voltage.

ok Thanks. Does channel resistance between Drain to source remains same as forward conduction during reverse conduction?

 

Does channel resistance between Drain to source remains same as forward conduction during reverse conduction?

If the MOSFET gate is biased on, yes.
If not, then it is the forward biased voltage of the substrate diode.

 

Here is something worth reading regarding the great characteristics of SiC for very fast diode response and low Vf of the body diode.

https://techweb.rohm.com/knowledge/sic/s-sic/04-s-sic/6147

 

SiC MOSFETs have a body diode that acts like this.
It is hard to build a circuit that drives the Gate any time there is reverse current. I have not seen it done much.

 

@ronsimpson is making us aware that if you spend a few minutes with a data sheet for an SIC MOSFET you will be better able to understand its operation.

 

SiC MOSFETs have a body diode that acts like this.
It is hard to build a circuit that drives the Gate any time there is reverse current. I have not seen it done much.

View attachment 284351

Thank you for this information.
So what i understood, if VDS is positively biased with VGS=18V, then Its forward Conduction, if VDS is negatively biased with VGS=18V, then Its reverse Conduction and when Vgs=0V/-5V then body diode will conduct. Is that right?