UCC28950-Q1: Need Technical Support for UCC28950 PSPICE TI model

The simulation results and the excel sheet design is attached here. Please go through the attachment.

3kW PSFB DC_DC converter.xlsx

Hello,

Could you share your schematic for review?

Regards,

Dear Mike, 

Please find the attachment.

UCC28950_TRANS.DSN

Hello,

Your inquiry is under review and I will get back to you shortly.

Regards,

Hello,

Could you tell me weather you ran the startup schematic or the steady state schematic in the file you attached?

Regards,

Hi Mike,

I tried with both Start_up model and Steady_State model. These results are shown in the below figures. In both case output voltage is not regulated at required nominal voltage of 52V.

Start_Up model simulation:

Steady_State model imulation:

...

Steady State model simulation

Hello,

Your inquiry has been received and is under review.

Regards,

Hello,

I reviewed your schematic and you used a transformer turns ratio of 5.  The tool recommended 4.4.  I wonder if you are running into a turns ratio limitation.  Could you change your transformer turns ratio and try running the simulation to see if it fixes the issue.

Regards,

Hi, Mike 

I have verified the simulation, schematic with excel design sheet. The transformer turns ratio is 5 only, even though the output voltage is not regulated at required value. I have attached the Excel design sheet, PSPICE simulation results and Simulation file. Please once again go through it. 

Do the needful.

https://docs.google.com/spreadsheets/d/1WKPTyXTWMtRZLvIixXv1_UvgAyo4IQ0WtGUUas0Dpsw/edit#gid=708519579

8228.UCC28950_TRANS.DSN

Hello,

I have received your inquiry and it it is under review.

Regards,

Hello,

I would try decreasing the transformer turns ratio to 4 and rerunning the simulation.

Regards,

Hello,

I modified the transient simulation and evaluated the transformer LS input to the design.  I have attached the modified design file for your reference. The primary turns ratio was changed to 5 similar to your design.

2870.UCC28950_TRANS.DSN

I reran the simulation and evaluated the voltage across the H Bridge and transformer.

I zoomed in on the voltage across the primary of T2 and the voltage across the H Bridge output (L2+T2 primary).

The voltage applied across L2 and T2 primary was 410 V and the voltage across T2 was 239V.  The voltage is being divided down when it should not be.

L2 = 26 uH, while the Lm of the transformer is 2.6 mH, with LLeak of 7.5 uH.  Even if there were and inductance divider this voltage would be 410V*2.6m/(2.6m+33.5uH) = 404.8 V roughly.  

There appears to be something wrong with this model and I am going to move it to the TI PSpice forum for further support.

Regards,

Hi Mike,

I've seen this once before. We didn't find a solution then.

I'll post this to Cadence as this is a component that they provide to see if they have a solution.

David

Hi Sugali,

Did you build the transformer following the app note by Cadence?Transformer Design_AppNote.pdf

Hi David, 

The already available transformer model (in TI PSPICE_UCC28950) is used here.

Thanks. I've shared the design file with Cadence. Let's see what they say about this not simulating correctly.

David

Hi David,

Thanks. Please go through this new design for 3.3kW PSFB DC/DC converter.

3kW PSFB DC_DC converter (2).xlsx4477.UCC28950_TRANS.DSN

HI Sugali

As the issue appears to be the transformer, let's see what Cadence says about it. Any resolution there should apply to the revised design.

David

Hi Sugali,

Can you archive the project and post that here. We need more than the DSN.

From capture, go to File->Archive Project and selet all the options to create a single archive file.

David

Hi David,

Thank you for your response. Here i'm attaching the Archive Project file. 

Please find the attachment.

Thank you.

Harinaik

UCC28950_TRANS-2024-03-07T09-59.zip

Thanks. That's a BIG file.

Hi David,

It is very important project. I request, please do the needful.

I've submitted it. I had to delete the .dat file as it was taking a lot of space. 

Hi David,

Any updates regarding 3.3kW DC/DC converter (UCC28950/UCC28951) TI_PSPICE simulation model.

We are going to make a 3.3KW charger with interleaved PFC + PSFB (DC/DC) topology. It is very important project for us and I kindly request you, please solve this issue as early as possible.

       Thank you.

Best regards,

Harinaik

Hi Harinaik,

I've pinged Cadence about this. Let's see what they say.

David

Hi Harinaik,

I referred this to Cadence as they own the transfomer model.

THey are unable to reproduce the problem.

Per their correspondence:

As described in the problem statement that the voltage across T2 was 239.
I checked it at my end and it does not seem to be 239 rather it is 400V which is expected as per the calculations shared by you.

Below are the snapshots for your reference, let me know if i misunderstood anything and we can have a call to discuss it further. I probed the voltage across T2 primary and the result is 




Cursor measurement for T2 primary is 400 as below

We might need to arrange a call to resolve the source of the difference.

Please let me know of your availability,

David

Hi David,

Thank you for your response.

Up to 28/03/2024 and after 03/04/2024 only I'm will be available.

If you don't have any other commitments, Tomorrow we can arrange a call.

Thank you

Harinaik

I've forwarded your email contact to Ayush.

Hi David,

Thank you for your support.

Best Regards:

Harinaik

Did you see his email asking for date/time preference?