Design of PWM for Cuk Converter using LM5025

I hope this is in the right place and apologize if it isn't.
Not too long ago I posted a thread about a Cuk converter that I was tasked with designing. Currently I have hit a snag yet again and hope that its as simple a fix as the last problem I had.

I am using an LM5025 as a PWM to help control the Cuk converter. I found a post online that showed a circuit schematic using only the LM5025. I built that circuit in PSpice and simulated it. Then I copied my Cuk converter over into the design and simulated it again. Both circuits can run just fine on their own, but when I connect the two I get problems. The voltage source connected to the gate of my MOSFET is a Vpulse with peak-to-peak voltage of 5V. I have also made a voltage divider at OUT_A of the LM5025 to get the voltage there to around 3.7V. I set the transient analysis as: Run time = 1ms, save data after = 0.1ms, max step size = 0.1ms.

When I connect the two circuits together I make a connection from the gate of the MOSFET (I remove the Vpulse) to the voltage divider. However the simulation never runs and always gives an error that says "ERROR(ORPSIM-15138): Convergence problem in transient analysis at Time= 208.7E-09". I'm unsure of what that means. I also believe that there might not be enough/too much current running through the MOSFET when the connection is made. If anyone could give any advise or point me in the right direction I would be very grateful.

Thank you for your time,
dtothec

I have attached pictures of both the Cuk converter and the LM5025 circuit, and the calculations I used to design the converter.

" have also made a voltage divider at OUT_A of the LM5025 to get the voltage there to around 3.7V."

Why would you want to do such a thing? And with 1 meg resistors?

When I run my Cuk converter if the Vpulse is set higher that 5V then it doesn't simulate. The voltage divider is so that OUT_A's voltage is halved, so that it will drive my converter. The only reason I used 1 meg resistors was that I just copied what was already there. As far as I know they can be changed.

Why did you select that controller?
The LM5025 is an active clamp controller, I don't see the clamp in your powertrain.

Even if there were a clamp, I'm always suspicious of claims of successful simulations for PWM controllers running open loop.

The powertain isection, one can simulate more or less by itself, by setting voltages and pulses. But a controller requires feedback, from several sources to simulate properly.

For instance....the comp terminal you got a fixed 5v supply. However, the datasheet clearly indicates that: "The external opto-coupler sinks current from COMP to control the PWM duty cycle."

Can you attach the netlist and cir files. May be I can try to play around the circuit and various options to see if it can be resolved.

Can you share the circuits (as suggested by Mvaseem) or complete circuit (where two of these modules are connected)? This would enable people to have a closure look.
Meanwhile - try following setting and see if this helps

- ITL4= 40
- ABSTOL=1n
- RELTOL= 0.005

MAX TIME STEP = 50n --- If this works, in next run try increasing this to higher value but this should be at least one order lower that switching time period.

The original poster has apparently disappeared without commenting the suggestions