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UCC24636 : How does it operate when entered into CCM mode?

Yoshwa
Expert 4050 points
Other Parts Discussed in Thread: UCC24636

Our customer is designing a UCC24636 application.

He asked how dose UCC26363 work when entered into the CCM mode condition caused by an abnormal operation such as an over load.

Of cause it has been designed in DCM mode condition.

What kinds of behaviors are considered?

  • 0
    TI__Expert 4015 points
    There will be a short period where both the primary FET and the SR are on together until the Vsc pin goes below the Vsc_en threshold. In general this is not destructive but this would need to be checked for the particular design.
    Thanks
    Billy
  • 0 in reply to Billy Long
    TI__Mastermind 26840 points
    Hello Yoshwa,

    The UCC24636 is designed to operate only with DCM and QR flyback controllers that do not allow CCM under any condition, including overload. If the primary controller allows CCM, the primary FET may turn on before the SR FET on-time is finished and cross-conduction will result until the primary controller turns off from its peak current limit detection. Depending on the speed of this current-limit detection and shut-off and the leakage inductance, the resulting cross-conduction peak current may or may not be high enough to be destructive to either or both of the MOSFETs.

    Regards,
    Ulrich