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UCD3138: How to turn off the secondary synchronous rectification drive when the UCD3138 is lightly loaded

zoujiangyilang
Genius 4560 points
Part Number: UCD3138

Greetings


We are in the reference UCD3138 29 full-bridge hard-switching development board  experiment,

we want to turn off the secondary synchronous rectifier drive at light load,

how do I modify the program, a reference case provided?


Thank you.

  • 0
    TI__Mastermind 18370 points

    Turning synchronus rectifiers off can be done by configuring the B outputs as GPIO by "DpwmxRegs.DPWMCTRL1.bit.GPIO_B_EN = 1;".

    The issue is that abrupt turn on/off of synchronus FETs will cause a dip or Hump at the output voltage.

    If you want to avoid this, you should softly turn off the sync-FETS by reducing the duty cycle gradually.

    UCD3138 provides a hardware mechanism for this purpose. You can configure one of the FE-ramp modules to sofly turn off the sync-FETs or you can do this gradually firmware interrupt.

    I do not have a reference code at the moment. But I think the manual (TRM) mentions this option.

    Regards,