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PMP5711: Understanding of the self synchronous rectification circuit for Wider input range.

Saunak Bhalsod
Prodigy 160 points

Part Number: PMP5711

Dear TI Experts

I have doubt on the self synchronous rectification stage used in the PMP5711. 

In one of the TI document (http://www.ti.com/lit/an/slua535/slua535.pdf) it has been told that If the input voltage range is wider than two to one, self driven synchronous rectification may not be an option and a control driven solution should instead be considered. But, in this case the range for Gate to source voltage is going higher than the 20V. Then For this zener diode has been used. 

I am making Active Clamp Forward Converter with Synchronous Rectification for the Input range of 16V to 50V and Output is 5V, 30A. Can I use the same self synchronous rectification circuit which is used in PMP5711. My target efficiency is above 90% at 50% to 100% load.

Thanks & Regards

Saunak

  • 0
    TI__Expert 6140 points

    Hi Saunak,

    The method that is used in PMP5711 can always be used, it is just a matter of how much power you are willing to burn in the linear regulator that is clamping the gate. The power that is lost is related to the switching frequency, the max voltage across the windings and the gate charge of the switching FETs.

    The circuit is mostly used because it is low cost and easy to implement. If you want improved efficiency, then driving the FETs with a controller might be better.

    Thanks,

    Robert

  • 0 in reply to Robert Taylor1
    Prodigy 160 points

    Hi Robert,

    Thank you so much for the response.

    I am interested in implementing the self synchronous rectification like PMP5711. Is there any related document for designing the self synchronous rectification circuit like PMP5711?

    I may keep the option for Controller driven gate pulse also. Hence, I can evaluate both the circuits.

  • 0 in reply to Saunak Bhalsod
    TI__Expert 6140 points

    Hi Saunak,

    I don't have a document to describe the gate drive circuit.

    However, I think you can use the circuit as described in PMP5711. The only thing you need to check is the max winding voltage based on your turns ratio and input conditions.  Then make sure bipolar transistor is rated for a higher Vce.

    Thanks,

    Robert

  • 0 in reply to Robert Taylor1
    Prodigy 160 points
    Hi, Robert,

    Thanks for your valuable support.