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UCC28780EVM-002: Unstable operation

Kenji Ohno1
Genius 5095 points
Part Number: UCC28780EVM-002
Other Parts Discussed in Thread: UCC28780

Hi Team,

My customers are evaluating using EVM.

Because EVM is performing unstable operation, they would like to know the cause.

· When starting with no load, in automatic restoration protection mode (entering a hibernation state with constant pulse), output slowly rises, it will start up in a few seconds.

· As the load is gradually increased up to 1A, the output droop once occurs at a certain place. It returns within 1 second.
　(It is presumed that protection operation is in operation during drooping)

・Although load can be drawn up to rating, output suddenly occurs temporarily when applying sudden load fluctuation. It is stable in steady state.

･After 1 week, the load restoration protection mode (over a load of 1 A or more goes into the hibernation state with constant pulse), and it can not be started at all.

Do you have advice on the above behavior?

Best Regards,

Kenji

  • 0
    TI__Mastermind 26790 points
    Hello Kenji-san,

    Thank you for your interest in the UCC28780 ACF controller. I'm sorry that your customer is experiencing trouble using the UCC28780 EVM.

    These EVMs are tested before they are shipped to customers. I cannot say for sure why that EVM is behaving as you described.

    Please ask your customer to check the input voltage source to see if it is limiting current to the EVM.
    If the source current is limited too low, it will not be able to provide peak power to the EVM during start-up and load-steps.
    This may result in the slow start-up or no start-up symptoms that you described. It may also account for output voltage droop or for sudden drop during a load step.

    Please check the test conditions at your customer site to make sure that there is more than enough source capability to support this 45-W EVM.

    Regards,
    Ulrich
  • 0 in reply to Ulrich Goerke
    TI__Mastermind 26790 points
    Hello Kenji-san,

    I have not seen a reply from you on this topic in a week. Is this still a problem, or has it been resolved?
    If it is resolved, please let me know so that I can close this thread.
    If you need more support, please provide waveforms of the unwanted behavior and the test conditions.

    Regards,
    Ulrich
  • 0 in reply to Ulrich Goerke
    TI__Mastermind 26790 points
    Hello Kenji-san,

    Having received no further response from you, I will closed this thread and consider the matter to be resolved.

    Regards,
    Ulrich
  • 0 in reply to Ulrich Goerke
    Genius 5095 points
    Hi Ulrich,

    I am sorry that the contact was very late.
    The problem has not been solved yet.
    EVM is not broken, I will purchase EVM additionally and plan to check the operation.

    The source power has sufficient capability.
    "For waveform acquisition, in the VIA section near the half bridge MOSFET
    We soldered conductors for probing.
    In the gate part of the GAN, measurement between the drain and the source was carried out in order to avoid noise application. "

    Best Regards,
    Kenji
  • 0 in reply to Kenji Ohno1
    TI__Mastermind 26790 points
    Hello Kenji-san,

    Thank you for your reply.

    I believe that several kinds of waveforms taken during the different conditions will be very helpful to debug this problem.
    Please capture a mix of long time sweeps to see the protection mode repetition rates, and fast time sweeps (or zoom with good resolution) to see the switching pulses.

    Regards,
    Ulrich