Clamp current calculation problem

Posted by: lonerzzz on 02/23/2014

Hello,

I have the two following sample files that are almost entirely based on default settings for which PI expert complains about the inability to calculate the clamp current and this occurs for all optimized designs. What can be done to resolve this or is this something that can be ignored? If so, please tell me why.

Thanks,

Jason

Files

SampleDesign1_0.uds (266.5 KB)

SampleDesign2_0.uds (266.5 KB)

Comments

You want to calculate the current in the snubber circuit when the controller is turned OFF. Am I right?

If I am right, then lest call the time when the power Mos-fet of the controller turns OFF "t=0". At t = 0 the current in the snubber is the same as the peak current of the DRAIN. As soon as the Power Mos-fet turns OFF, part of the charge is deviated to the snubber and part of charge still flowing inside the Mos-fet because the internal capacitance it has.

You can see this interesting document (see link below) that explain some features of the DRAIN snubber.

http://www.onsemi.com/pub_link/Collateral/TND396-D.PDF

Hope I answered your question

Thanks for attempting to respond but I am not sure what to make of the information you provided in relation to the error that I am seeing in PI expert. The software complains that the clamp current cannot be calculated even though it says that is has optimized the design. This is what I don't understand and what I need more information about. To me this looks like an error with the software because it has chosen invalid components. The software is telling me to choose a bigger device although the choice of device was automatically made by the software. Even with a bigger device, the problem still remains.

I am sorry for my misunderstood. It was not clear to me but now I know what you mean.

I sent an email to the software programer about this issue. As soon as I get an answer I will reply to you

Jason:

I was talking with software team about this issue. They told me to thank you becasue you found a bug in the program. They do not have a fix yet but they are working on it. Software team said you can use the clap recomended by the program.

Thank you so much and I appologise for the inconvenient

PI Worf

Thanks for the response. I will assume that the error is noise.