UCC3895: problem in feedback circuit

Hi Pradeep,

Thank you for the querry on UCC3895.

I looked into the schematic and it looks like the CC-CV loop is implemented more in line with the PMP-8740 design. Can you please refer this design and PMP9622 for details on the implementation?

Please feel free to share other design specifications like the power level, input output voltages etc. It will be great if you can share excel calculator/PSPICE/TINA model which you have developed to cross check the issue.

Also, TI India will be on festival holidays next week. Please expect a delay in response from our end.

Regards,

Harish

Hi Harish,

Thankyou for your reply.

I implemented the CC CV loop from PMP-8740 but that reference design in ON UCC28950 and i am using UCC3895dw, so there must be something i am not doing correctly.

I am working on 3KW battery charger (60v, 50Amp max) and i want to control the charging current and voltage using a MCU that's why i implemented the CC CV loop from PMP-8740.

Also i haven't used any .excel calculator or anything for calculation. 

Hi Pradeep. Since 10/24 & 10/25 are TI Holidays in India, Harish will be unavailable for a few days. Mike O. will try to support this issue during his absence. Thank you for your patience.

Ray

Hi Pradeep,

Can you please try the following steps let us know your observations?

1. Your schematics are not annotated properly. Please re-annotate and upload it to refer to components easily.

2. Some signals of the controller are referred to PGND when the controller is sitting in the GND side. Please verify them again.

3. Please clarify on the connection between nets V_FB and FB_ISO

4. Run the CV loop first, similar to PMP9622 by disbling one of the ORing diodes in the feedback path. 

5, Please post some test waveforms in open loop (vs closed loop) where you mention the converter as working along with test conditions to help debug better along with information of duty cycle, E/A output voltage, CS signal etc. 

Thank you

Regards,

Harish

Hi Harish,

Thank you for your Reply.

For point 1, 2 and 3 I am attaching schematic again.

I am also on leave right now so i will upload the waveforms later when i will join the office.

Also can you share your email id so that i can share board file with you maybe there is some problem in my layout.

Thank you 

Regards,

Pradeep

0728.DC TO DC CONVERTER.pdf6787.PSFB.pdf .

Hi Pradeep,

Thank you for sending the schematic. Please let us know your inputs on points 4 and 5 once you are back in office and I will check the schematic during this time.

Regards,

Harish