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  1. #1
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    Using TLVH431 for SMPS with Vout=36V?

    Hello,

    I wish to use the TLVH431 to get opto-isolated feedback in an SMPS.

    The problem is that this SMPS has an output voltage of 36V, and the maximum allowable cathode voltage of TLVH431 is 20V.

    Do you think that it is possible to use the TLVH431 here?

    Is it right that all I have to do is simply put a 20V zener in series with RS inn the following schematic?
    -and then I am safe?

    SCHEMATIC:
    http://i51.tinypic.com/30skly9.jpg



    TLVH431 DATASHEET:
    http://focus.ti.com/lit/ds/symlink/tlvh431.pdf




    RELEVANT ARTICLE:
    Article: Biasing the TL431 for improved output impedance :
    http://powerelectronics.com/mag/50107.pdf

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    Re: Using TLVH431 for SMPS with Vout=36V?

    The topic has been discussed at edaboard before, you did also take part in the discussion by the way.
    See e.g. https://www.edaboard.com/thread143544.html
    Last edited by FvM; 30th December 2010 at 23:57.


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  3. #3
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    Re: Using TLVH431 for SMPS with Vout=36V?

    hi

    thankyou for reminding me of that thread, which i have read many times, and each time i learn something new.

    but the zener in that thread, in my opinion is placed wrongly............the way it is in thread 143544, it would badly affect transient performance, and also be wasteful of energy

    do you agree?

    I think the place for the zener is in series with RS in the schematic of my post above top.(?)

    The TLVH431 does not care what its cathode voltage is, (as long as its below 20v )......all it does is draw as much current through its cathode as it takes to keep its reference terminal at VREF = 1.24V (?)
    Last edited by eem2am; 31st December 2010 at 01:45. Reason: mis-spell



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    Re: Using TLVH431 for SMPS with Vout=36V?

    The transient compensation is actually affected by the zener diode circuit, for that reason, the circuit had been changed later on. The main reason for shunt connection of the zener diode is the high output voltage of 200 V. In your case, a series connection may be the easy way.


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