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

 

Are you trying to mimic the "Typical Application" on the data sheet? I saw at least one difference in your schematic versus that (the PLLIN is grounded in the data sheet version).

I confirm that your simulation produces ~11.6V at the output, not 40V.

 

Are you trying to mimic the "Typical Application" on the data sheet? I saw at least one difference in your schematic versus that (the PLLIN is grounded in the data sheet version).

I confirm that your simulation produces ~11.6V at the output, not 40V.

Hi yes realised I made that mistake and ammended it the output is not quite as good as I would like, I wanted to see if I could get it to function under continuous conduction mode.

 

I have got it working now the only thing I'm unhappy about is the amount of ripple voltage on the output does anybody have any suggestions fort this?

Kind Regards

Art

 

hi 547,
This is your circuit using good quality low ESR commercial capacitors on the Out and Inp Voltages
E

EDIT:
For comparison your original circuit is shown in A002 image.

 

hi 547,
This is your circuit using good quality low ESR commercial capacitors on the Out and Inp Voltages
E

would you mind posting up the improved LTSpice file, also any recommendations for which capacitors? The capacitors have been my main concern especially finding suitable ceramic ones because of their lower ESR values and suggestions would be warmly welcome.

 

hi 547,
Here it is.
Note the Manufacturers data is shown in the pop up menu.
Choose the voltage rating to suit the circuit.
E