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UCC27614: Having trouble to simulate in Pspice for TI

Rinya Uchiha
Prodigy 80 points
Part Number: UCC27614
Other Parts Discussed in Thread: LM3481, UCC27524, UCC27322, CSD

Hello, 

I am trying to use this low-side gate driver to drive this mosfet for a flyback converter. The transformer is 1:1 ratio, 12uH primary inductance, 150nH leakage inductance, and around 0.015-ohm resistance for both sides. 

I have this 12V DC on the primary side and it is expecting 12V at the output (Secondary side). I often run into the error "These voltages failed to converge" for the Pspice simulation when modifying the parameter/circuit connection to try to get it to work. Even if I take the gate driver out and connected the PWM signal directly to the mosfet would often to have failed to converge error. I suspect it is my circuit problem but I am not quite sure why it is not working because I have used exactly the same circuit to simulate the LM3481 (Instead of UCC27614) before and it was working fine. 

Best Regards, 

Rinya

  • 0
    TI__Genius 11770 points

    Hi Rinya,

    There is currently an issue with that model which may be causing the convergence issue. We are working on it now. 

    In the meantime, you can get basically the same performance from using the UCC27524 model and tying its outputs and inputs together. 

    Or, you could use UCC27322, which is a very similar device. 

    Also, using these models can rule out the circuit as the issue, since they are both known good models right now. 

    Thanks,

    Alex M.

  • 0 in reply to Alexander Mazany
    Prodigy 80 points

    Hello Alex, 

    Thank you for replying. However, I have tried to use UCC27524 and UCC27322 on the Pspice for TI, and both of them have the same failed to converge error.

    Best Regards, 

    Rinya

  • +1 in reply to Rinya Uchiha
    TI__Genius 11770 points

    Hi Rinya,

    Sorry to hear that. Personally, I would try reducing the required accuracies in convergence settings. Besides that though, I would use the "power NMOS" model instead of the CSD, and the parameterized "power diode" model wherever possible, just to see if that helps. I would also connect R2 to GND instead of across the windings like that. 

    Lastly, I would try using coupled inductors instead of the PSpice transformer. 

    You can adjust the magnetizing inductance and coupling factor also, which is good to look at. I don't know if it will help convergence, but I do think its probably worth doing.

    As for why LM3481 didn't have this issue, its really hard to say. I don't see how that could converge but a PWM directly to the FET would cause issues. Please let me know if any of these suggestions work.

    Thanks,

    Alex M.

  • 0 in reply to Alexander Mazany
    Prodigy 80 points

    Hello Alex, 

    I changed the diode and MOSFET to the power-parameterized version. and tighten the R2 to the ground. I had the transformer as it is just to test if it would be a spice transformer issue. but it turns out I got the output as expected. 

    iI tried to change it back to UCC27614 block, and it was having the converge issue again. So I think i will stick with this component. Thank you so much for the help. 

    Best Regards, 

    Rinya