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pmg1996
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1496267784Si-IGBT-and-SiC-MOSFET.jpg

Hello 

I am designing an inverter using Infineon's sic module FS33MR12W1M1H_B11 or FS28MR12W1M1H_B11.

 

My question is none other than the body diode.

I understand that in the case of IGBT modules, diodes are additionally installed on the module for reverse current.

Conversely, I understand that MOSFETs allow reverse current to flow.

Then, the two sic modules I use do not have additional diodes installed?

For example, in IGBT, forward current flows through IGBT and reverse current flows through diode.
When the forward current flows through the mosfet to the sic mosfet, does the reverse current flow through the mosfet or the diode?

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Guru_Prasad
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250 replies posted 100 solutions authored 25 likes received

Dear @pmg1996 

 

Greetings!

My answers are mentioned below 

Then, the two sic modules I use do not have additional diodes installed?

Answer: The above mentioned two MOSFET modules are having inherent body diode no need to add the additional diode 

For example, in IGBT, forward current flows through IGBT and reverse current flows through diode.
When the forward current flows through the mosfet to the sic mosfet, does the reverse current flow through the mosfet or the diode?

Answer:

IGBT :Yes, your understanding is correct when current is negative  the diode conducts 

 

MOSFET : Since, MOSFET is bidirectional device the current will flow in both direction(forward and reverse) when Gate voltage is applied above threshold . when  gate voltage below threshold voltage MOSFET diode will work for negative current instead of MOSFET.

Note: the revere current will flow in MOSFET and diode the path is decided by Gate threshold voltage 

 

Thank you

Guru

 

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Guru_Prasad
Moderator
Moderator
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250 replies posted 100 solutions authored 25 likes received

Dear @pmg1996 

 

Greetings!

My answers are mentioned below 

Then, the two sic modules I use do not have additional diodes installed?

Answer: The above mentioned two MOSFET modules are having inherent body diode no need to add the additional diode 

For example, in IGBT, forward current flows through IGBT and reverse current flows through diode.
When the forward current flows through the mosfet to the sic mosfet, does the reverse current flow through the mosfet or the diode?

Answer:

IGBT :Yes, your understanding is correct when current is negative  the diode conducts 

 

MOSFET : Since, MOSFET is bidirectional device the current will flow in both direction(forward and reverse) when Gate voltage is applied above threshold . when  gate voltage below threshold voltage MOSFET diode will work for negative current instead of MOSFET.

Note: the revere current will flow in MOSFET and diode the path is decided by Gate threshold voltage 

 

Thank you

Guru

 

hello.

Thanks to you, I learned that unlike IGBT, MOSFET does not require an additional diode.
I would like to ask you further questions.

I would like to ask a question in the environment of a 2LEVEL inverter.

1] I know that when calculating the conduction loss of a MOSFET, the resistance RDS(on) is used when the forward current is flowing. So how do I find the conduction loss for the reverse current flowing through the diode?

2] In the case of IGBT, when calculating the conduction loss, is it correct to ignore the reverse current flowing through the diode and calculate only the forward current flowing through the IGBT?

3] I understand that when estimating the temperature of the IGBT, the reverse current flowing through the diode is ignored and only the forward current is calculated. So, is it true that both forward and reverse currents should be considered when estimating the temperature of a MOSFET?

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Guru_Prasad
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Moderator
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250 replies posted 100 solutions authored 25 likes received