# Reverse Conduction operation of SiC MOSFET

#### alison_941

Joined Dec 21, 2022
18
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

#### Ya’akov

Joined Jan 27, 2019
9,264
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.

#### crutschow

Joined Mar 14, 2008
34,827
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.

#### ronsimpson

Joined Oct 7, 2019
3,203
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.

#### alison_941

Joined Dec 21, 2022
18
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?

#### alison_941

Joined Dec 21, 2022
18
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?

#### crutschow

Joined Mar 14, 2008
34,827
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.

#### ronsimpson

Joined Oct 7, 2019
3,203
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.

#### DickCappels

Joined Aug 21, 2008
10,246
@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.

#### alison_941

Joined Dec 21, 2022
18
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?