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Synchronous Rectifier Controller for Forward Converter

K.Yaita
Guru 29710 points
Other Parts Discussed in Thread: UCC24630, UCC24610, UCC24636, TPS28225, ISO7420FE

Hi Team,

I understood UCC24630 is only suitable for controlling the freewheeling diode in Forward Converter as the following.
https://e2e.ti.com/support/power_management/isolated_controllers/f/188/p/435245/1585306#1585306

Is there any Synchronous Rectifier Controller that can control the forward diode for Forward Converter?

Best Regards,
Yaita

  • 0
    TI__Mastermind 31580 points
    Hi Yaita-san,

    Let me ask the system engineer for the product to answer this question.

    Regards

    Peter
  • 0 in reply to Peter Meaney
    Guru 29710 points

    Hi Peter-san,

    Thank you for your support.

    For your reference, I assume LM5021-2 for forward converter on primary side.
    I will wait for your team's reply.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Expert 7395 points

    Hello Yaita-san,

    You can use the UCC24610 as the forward diode replacement with a MOSFET. It uses Vds sensing, not Volt-second sensing like UCC24630/UCC24636 so it is not dependent on the topology. If used for an output voltage greater than 5V it would have to have a separate bias and clamping. Further, instead of having the "forward MOSFET" on the high side, you would instead put it on the low side so that the source is connected to ground. See reference design here where it was used with LLC:

    Regards,

    John

  • 0 in reply to John Stevens
    Guru 29710 points

    Hi John-san,

    Thank you for your support!

    I believe it isn't necessary for LM5021-2(primary side PWM controller) to control UCC24630 and UCC24610 if my customer designs synchronous forward converter by these three devices.
    Is my understanding correct?

    Your support would be appreciated.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Expert 7395 points
    Yaita-san,
    You are correct. these UCC24630 and UCC24610 will work fine with any controller as primary forward controller. they just need to operate within timing parameters constraints.
    Regards,
    John
  • 0 in reply to John Stevens
    Guru 29710 points

    Hi John-san,

    Thank you for your support.
    I understood.

    In other ways, I believe TPS28225 is usable for synchronous rectifier driver for forward converter.
    It could be one chip solution but needs to be controlled from primary controller same as the following Figure 37.
    Is my understanding correct?



    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Expert 7395 points

    Yaita-san,

    Yes, you could do that. But then you would require a pulse transformer and external rectification components  as seen below (or a digital isolator like ISO7420FE) to send the signal across the iso boundary from the Primary controller. The UCC24610 and UCC24630 do not require that extra chip. Additionally, the UCC24610 and UCC24630 offer some flexibility in the timing to optimize efficiency, where as the TPS28255 is fixed based on primary timing.

    Regards,

    John

  • 0 in reply to John Stevens
    Guru 29710 points

    Hi John-san,

    My customer designs forward converter with TPS28225 and has some concerns about it.
    Could you check his schematic?

    If the answer is yes, I would like to send his schematic on off line.
    May I have your e-mail?
    yaita-k@clv.macnica.co.jp

    Yaita / Japan disty