LTSpice Boost Converter Simulation and Improvement

[artmaster547]

Hi All

I have setup a simulation in LTSpice with components selected that I wish to create a real PCB for but wanted to simulate it first.
I am having a it of an issue with the design I used LTpowerCAD initially to workout what components to use, It takes in 12V and outputs 40V @ 7.5A. However when simulating it does not produce the output waveform expected I feel like I am missing something trivial any help would be appreciated. Simulation is attached with this post. Any suggestions for improvements or reduction of any noise would also be appreciated.

Kind Regards

Art

 

[CataM]

MOSFETs not switching, hence output voltage is 11.3V. Check the design provided by LTpowerCAD again... You must have wrongly connected something.

 

[crutschow]

What output waveform do you expect?
How are we to know what problem you are having if you don't tell us?

You have the SS (Soft Start) capacitor much larger than shown in the test circuit (why?) which is delaying the start of the switching.
Change it to 0.005uF or less. I used 0.001uF for my simulations.

You have "X" terms in you output capacitors. I'm not sure LTspice accepts that. Just use the total capacitor value.

There is ringing in the output due to the Equivalent Series Inductance you added to the output capacitors.