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Unwanted oscillations in flyback simulation (LTSpice)

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LaMontagne

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Hello,

I am currently working on a simulation for a bidirectional flyback circuit (output diode replaced by a NMOS). When I am using generic components, everything works fine. However when I use
manufacturer supplied spice models for the MOSFETs, I keep getting unwanted oscillations while the mutual inductor is charged (current ramping up).

I assume the oscillations come from the LC tank consisting of the transformer primary inductance and the MOSFET parasitic capacitance. Could this be a simulation problem? I attached the waveform of the transformer primary current showing the oscillations. Iprimary.PNG

Thanks for any help!
 

In contrast to simulation artefacts, the oscillations look smooth and the waveforms plausible at first sight. You must know if the parameters of your simulation have been selected according to real-world circuit parameters. The oscillation during ton looks somehow strange, probably due to unusual or unrealistic circuit parameters. Viewing the LTSpice design could clarify things.
 

Thanks a lot for the response. Here is the circuit I am trying to simulate:
Flyback.PNG

It seems that these oscillations are less of a problem if the on-time is higher. Can I expect to see similar oscillations in the real circuit? (I ask this as I would like to avoid using any RCD clamps etc. if possible)
 

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