CAS350M12BM3 LTspice moduel Qustion. FullBridge_LLC simulation.

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Recently, I have been using the power module CAS350M12BM3 to design a 60kW full-bridge LLC circuit. I downloaded the LTspice model and tried to simulate my circuit using LTspice. During the simulation, there were several questions that confused me:

1.Does the LTspice model of CAS350M12BM3 include the equivalent junction capacitance parameters between the D and S terminals of the device? At present, my method is to parallel a 1100pF capacitor (referring to the Coss on the Datasheet) between DS for simulation, but this will hinder the Mosfet from working in the ZVS state. Do I need this capacitor, and if so, how do I determine its capacity?

2.When I used the drive circuit in Figure 2 to drive the CAS350M12BM3, the gate voltage spike of the H MOS of the module was much larger than the L MOS. I don't understand what caused the problem. How do I adjust the circuit to eliminate spikes?

60kW ZVS LLC Resonant converter.asc

Forum_Moderator

Thank you for your post, it has been approved and we will respond as soon as possible.

Bdeboi

Hello,

1. The model already includes the device capacitances from D-S, G-D, and G-S. The model is fully functional as-is and you shouldn't need to add any additional components to adjust its behavior.
2. I'm seeing pretty similar behavior between the high-side and low-side devices (see below). Could you provide more insight on what you are seeing? Are you measuring across G/K? To properly measure the gates, you need to probe, for example, V(G1,K1), and not V(G1). The latter is a ground-referenced measurement which is not correct. Upon further inspection, I've found the issue to be with the modified trap solver in LTspice. Go to tools → control panel → SPICE and select either 'gear' or 'trapezoidal'. This should solve your issue.

If you have any more questions or information to help solve these issues, please let me know and I'll be happy to help.

Thanks,

Brian

BlakeNelson

I hope that this answered your question. I will close this discussion for now but if you have a follow up question, please "Start a New Discussion" and we would be glad to support you further.

Blake