UCC28630: Output Voltage is low 13.4V instead of 24V

Hi Raghu,

Thank you for the query on UCC28630.

1. Please provide us your latest schematics to review.

2. Can you check with a resistive load/ electronic load at full rated power before trying to start with FAN?

3. The pdf calculations sheet attached shows "red" coloured cell which signifies violation of timing design constraints due to inappropriate choice of Rcs and Lpri. I would suggest tuning this properly (mostly increasing the Lpri)

4. Ra and Rb needs to be adjusted to get regulation to 24V. The fact that you were able to get it to upto 20V s encouraging. Please use the recommended values as per calculator.

5. Can you please check the below post to see what fault you are observing

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/545420/ucc2863x-fault-cause-codes?tisearch=e2e-sitesearch&keymatch=UCC28630%252520AND%252520fault%252520code#

Regards,

Harish

Thanks Harish san for the quick reply.

Schematics is enclosed. Power supply section is taken from TIDA-00386 and no modification. Motor control section is our design.

We had some difficulties in getting the transformer, so we worked on without resolving the Lpri & Rcs error. The Wurth transformer Primary and secondary winding ratios are matching with Renco. But the Bias winding is 7 turns in Wurth in Renco its 4. so thought buy adjusting the Ra and Rb  we will move forward.  we are getting the transformer developed.

I will go through the post as you suggested.

Regards

RaghuPNW18_Mirai_Schematic_W05042023.pdf

Hi Raghu,

Please keep us posted with the new transformer results.

Thank you

Regards,

harish

Hi Harish,

We received the transformer samples from local vendor. As per the winding ratio of Renco and Primary Inductance is matched to 260uH.

When switched on output is 24.4V and Fan BLDC motor is running fine till 210rpm. When the Fan is put into 370rpm (speed 5), after 15seconds power supply switches off.

The motor is 24V 1.5 A BLDC motor.

Any suggestions what we need to do to as next steps. If any additional inputs required I will provide.

Thanks and Regards

Raghu

Hi Raghu,

Thank you for the reply.

I suggest referring to this post to identify the fault code which is present at the time of fault/ shutdown. It would be helpful in debug.

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/545420/ucc2863x-fault-cause-codes?tisearch=e2e-sitesearch&keymatch=UCC28630%252520AND%252520fault%252520code#

Regards,

Harish