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TIDA-00776: Assistance Needed for TIDA-00776 350W Reference Board - IC Failure and Overvoltage Issue

Mohd Sahid
Prodigy 40 points
Part Number: TIDA-00776
Other Parts Discussed in Thread: UCC28180

Tool/software:

Dear TI Support Team,

I hope this message finds you well. I am currently working on implementing the TIDA-00776 350W reference design for a PFC circuit, but I am encountering a critical issue that I hope you can help me resolve.

The problem I am facing is that the PFC IC burns out during operation, and the output voltage exceeds 550V, which is far beyond the expected range for this design. I am using an external 12V lab supply for the UCC28180, and my startup sequence involves first applying AC and then powering the 12V DC. Despite following this sequence, the board is not functioning as expected.

Additionally, I have set the Vsense voltage to 5V in the circuit, which is intended to correspond to an output voltage of 400V. However, the circuit is still producing a much higher output voltage than expected.

Could you please provide guidance on why this might be happening? Specifically:

  • Is the startup sequence I am using potentially causing the issue?
  • Could there be a problem with the feedback loop or overvoltage protection in the reference design?
  • Are there any recommended troubleshooting steps or common pitfalls associated with using the TIDA-00776 reference board in this configuration?

I would greatly appreciate any insights or recommendations to prevent the IC failure and correct the overvoltage problem.

Best Regards,
Mohd Sahid

  • 0
    TI__Prodigy 750 points

    Hi, Mohd

    I believe it's the feedback issues, could you double check your feedback circuit, see if it works well? you can apply a dc voltage on DCBUS, see if the Vsense is proportional to the DCBUS voltage.

    Regards

    Hely

  • 0 in reply to Hely Zhang
    Prodigy 40 points

    Hi Hely,

    Thank you for your response. I have double-checked the feedback circuit, and according to my calculations, the Vsense divider is set to provide 5.00V for a 399V DC bus. This configuration aligns with the expected voltage range.

    To further troubleshoot, I removed the IC and applied 220V AC, which resulted in a rectified DC voltage of 312V, as expected (√2 × Vac). Up to this point, everything appears to be functioning normally.

    However, when I turned on the12V External supply without the IC installed, the DC voltage started increasing rapidly beyond control.

    Could you provide further insights into why this might be happening when the IC is removed, and why the voltage increase occurs so rapidly without any control?

    Thank you for your continued support.

    Best regards,
    Mohd Sahid

  • 0 in reply to Mohd Sahid
    TI__Prodigy 750 points

    Hi, Mohd

     DCBUS voltage should be proportional to AC input voltage assuming you have diode bride/boost inductor/boost diode/Electrolytic capacitors topology, since you already removed IC, not sure why DCBUS voltage increase when you power on external 12V supply

    Can you provide your schematic of PFC?  and what kind of 12V supply do you use? isolated 12 supply?

    Regards

    Hely

  • 0 in reply to Hely Zhang
    Prodigy 40 points

    Hi Hely,

    Thank you for your prompt response.

    I have attached the schematic of the PFC circuit for your reference(TIDA-00776). As for the external 12V supply, I am using a lab power supply for the 12V DC input.

    To further investigate the issue, I removed the bulk capacitor and checked the voltage at the output terminal. When the 12V supply is connected, the voltage spikes to around 650V. Without the 12V supply, the output is stable at 312V for a 220V AC input.

    It seems that the connection of the 12V supply is triggering this uncontrolled increase in voltage. I would appreciate any further insights you may have on why this might be happening.

    Thank you for your support.

    Best regards,
    Mohd Sahid

  • 0 in reply to Mohd Sahid
    Prodigy 40 points

    Hi Hely,

    Thank you for your feedback.

    I initially used an external lab power supply. However, I have now replaced it with a step-down transformer that converts 220V AC to 22V AC, followed by an LM7812 regulator to provide a stable 12V DC.

    After making this change, the issue has been resolved, and the circuit is now working as expected, with proper voltage regulation.

    Thank you for your support during this troubleshooting process.

    Best regards,
    Mohd Sahid

  • +1 in reply to Mohd Sahid
    TI__Prodigy 750 points

    Hi, Mohd

    Sorry for late reply.

    Thanks for let us know your final result.

    I think the reason could be your previous lab power supply is not fully isolated one, or because the DC- is actually grounded.

    Regards

    Hely