TINA /香料/ UCC2897A： The EVM simulation doesn't have soft-switching on the main Mosfet.

Andy Chen36

Intellectual 640 points

Part Number: UCC2897A
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

I found the UCC2897A EVM simulation file. There is not soft-switching appearance on the main MOSFET.

The VDS & IDS on Q2 are crossovered.

Andyslum606.tsc

over 6 years ago

0 Peter Meaney over 6 years ago

TI__Mastermind 31580 points

Hi Andy,

Let me check it. There may well be some differences in the parasitic components, inductance and device capacitance that is making the difference between the EVM and the simulation.

Regards

Peter

0 Peter Meaney over 6 years ago in reply to Peter Meaney

TI__Mastermind 31580 points

Hi Andy,

Sorry for the long delay, I remember I did start looking at the simulation but I was directed onto other tasks. I have rerun the simulation and extended the delay between the main fet and clamp fet by increasing the RDEL resistor to 30k. This allows the main fet to achieve ZVS.

Please note that different values may be required between the simulation and hardware to due non-linear variations in semiconductor capacitances and variations in leakage inductance in transformers.

Regards

Peter

0 Andy Chen36 over 6 years ago in reply to Peter Meaney

Intellectual 640 points

Hi Peter
Could you show me the wave about Vds & Ids of main mosfet?

Thanks
Andy

0 Peter Meaney over 6 years ago in reply to Andy Chen36

TI__Mastermind 31580 points

Hi Andy,

I must have changed something else with the file when I changed the RDEL resistor to 30K as I didn't get ZVS when I only made that change this time. I re ran the sims a couple of times and tuned the transformer by reducing the Lm to 40uH and leaving RDEL at 8.5k.

I change Lm to 40uH and Lk to 1uH. In the real application Lm will have to be adjusted along with RDEL to optimize the ZVS performance of the design.

Regards

Peter

0 Peter Meaney over 6 years ago in reply to Peter Meaney

TI__Mastermind 31580 points

Hi Andy

I hope you have made progress on this topic, since there has been no reply since my last post I am going to close the post. Please open a new post if you have another question.

Regards

Peter