Rise Time of Simscape MOSFET models

I am modeling a H-Bridge to power a simple inductor in Simscape. The driving frequency is supposed to be 50kHz. (I would like to upload the .slx file so you could see it, but I didn't find the function, if there is one.)

The issue I get is that the mosfets take a considerable time to turn on. The problems are that the mosfets that I will use later will turn on much faster than in the simulation, and that apparently the rise time does not depend on the frequency, it always appears to be about 1/4 period. I have tried several models, but the one that I could make work best is this one: https://de.mathworks.com/help/physmod/sps/ref/mosfet.html

The schematic itself is not that complex, it is just a square wave (50% duty, 10V ampl) into a S->PS into the mosfet. The adjustment of the duty cycle is done by a phase shift between the two half bridges. The release is r2018b by the way, but I couldn't choose that one, so I chose the closest.

Thanks in advance for any help, Ivo

Answer 1

[Ivo Trausch]

Hello Joel,

Thank you for replying, but the error has been found just a while after posting.

We had a typo in our script that defined all our timings; I aimed for 1us lockout between the two half bridges, but by swapping the variable names by mistake, we created 1us of overlap. (facepalm).

Sorry for not updating the community, I had forgotten I posted this.

Answer 2

[Joel Van Sickel]

Hello Ivo,

the piecewise linear mosfet models which I think you linked to (the link is old so I'm not sure) should be turning on instantly. There is probably an issue with the solver time step or how the signal is being fed to the mosfet. If you click the image of the paper clip, you can upload a model, and we can give specific guidance on how to use it. Here is an example of turning a mosfet on and off, there is no turn on delay. https://www.mathworks.com/help/physmod/sps/ref/mosfetidealswitching.html

If you use the more detailed n-channel mosfet, then you can simulated delay, but it will be based on your parameters for the mosfet and the drive circutiry, so that you can match the actual turn on time of the real device.

Regards,

Joel