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## Calculate Switching Losses vs Drain-Source Voltage and use it in plecs

Level 1
Level 1

Hi there,

I already asked a similar question in another forum, but now I want to know for sure. I try to calculate the power losses off a selected FET with plecs. For that I tried to calculate the losses with the  given formula shows in the appendix "Eon_Mosfet". On the other hand, there is the possibility of this via the given paper "ApplicationNote...".

Firstly, I tried to calculate the losses behaviour with the given "ApplicationNote..." paper.

This one says that the switching losses via Tj (T_Junction), Gate Resistance, Ids and Vds  have a significant contribution to the power losses. While I can insert the first three factors into PLECS, I'm missing the information about the losses over Vds. The paper says: "This information is not included in the datasheet due to the linearity of this dependence." That means the switching losses via Vds isn't include in the datasheet, but I assume they exist a way to calculate the approximate course (shows in appendix - "E=f(Vds)"). Presumably even without measuring it experimentally. Am I right?

On the other hand I found the paper: "MOSFET Power Losses Calculation Using the Data-Sheet Parameters".

For example, with the given information (shows in the appendix "Eon_Mosfet"), I would calculate the switching losses (Eon) of the FET using the formula and calculate this with different values ​​(Udd, Idon) and calculate an approximated function. Then I would insert the function into Plecs. Is this a possible way or would that falsify my simulation results?

1 Solution

## Re: Calculate Switching Losses vs Drain-Source Voltage and use it in plecs

Moderator
Moderator

Hi,

Double pulse test will give you the switching energy details based on your variable selection.

You can try this in another way using the formula as discussed.

Qoss and Coss can be derived using the integration. coss is the small signal capacitance. integrating the coss curve with respect to the voltage will provide you the  Qoss. the same  can be tried to find Eoss.

Regards,
vignesh kumar

5 Replies

## Re: Calculate Switching Losses vs Drain-Source Voltage and use it in plecs

Moderator
Moderator

Hi,

Thanks for posting on the Infineon community

Do you consider any specific part number?

Regards,

Vignesh kumar

Attachments are accessible only for community members.

## Re: Calculate Switching Losses vs Drain-Source Voltage and use it in plecs

Level 1
Level 1

Hi,

I selected the IMZ120R045M1 FET. I can try to describe in detail what I have done so far.

First I inserted all available diagrams into Plecs. There is a picture of each in the appendix (E=f(Ids), E=f(Rg(ext))...). Since I don't have any information about the losses over Vds, the formula to calculate that is not included in the final formula yet.

The final formula which you can find in the plecs ide looks as shwon in the picture "Formula".

## Re: Calculate Switching Losses vs Drain-Source Voltage and use it in plecs

Moderator
Moderator

Hi,

you can simulate a Double pulse test to get the losses due to the Vds,

you can keep the remaining parameters constant.

Regards,

Vignesh kumar

Attachments are accessible only for community members.

## Re: Calculate Switching Losses vs Drain-Source Voltage and use it in plecs

Level 1
Level 1

Thanks for your answer. I think I found an another way. But I if I get simular values with the double pulse simulation I valudate my calculated values.

What I've done:

With a simple integral of Coss from 0 to 1000 V drain source voltage (Vds) I get the electrical charge over Vds. After that I integrated Vds over the electric charge. In the appendix you can find the formula I used. What's your recommandation?

## Re: Calculate Switching Losses vs Drain-Source Voltage and use it in plecs

Moderator
Moderator

Hi,

Double pulse test will give you the switching energy details based on your variable selection.

You can try this in another way using the formula as discussed.

Qoss and Coss can be derived using the integration. coss is the small signal capacitance. integrating the coss curve with respect to the voltage will provide you the  Qoss. the same  can be tried to find Eoss.

Regards,
vignesh kumar