This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS92210: calculation is case non-isolated(PMP3672)

Part Number: TPS92210
Other Parts Discussed in Thread: PMP3672, TPS92075, PMP4347, TPS92314


Hello

Thank you for your cooperation usually.

Customer think TPS92210 (PMP3672) seems good solution for their next project.

Customer changed spec  to follow PMP3672 as per your advice.

<customers spec>
Vin  
85-230V

Vout
70V ( 2.4V * 28 series =67.2V)  ==>change spec==> 2.4V * 14= 33.6V

Iout 
400mA =>change spec==> 800mA


size  30mm x 18mm x 8mm for T8 tube
( non-isolation topology should be fine)


Question

I did not find out calc tool in case non-isolated for TPS92210.

Customer want to customize PMP3672.

I see TPS92210EVM Design Tool 11.01.26 is for isolated only.


Q1

How do we calculate L4,L5 if LED current increased ?(PMP3672(50V/0.35A  default: 56uH + 56uH)

If LED current was 800mA, it should be calculated as

0.35/0.8  *56  24.5uH + 24.5uH?

( Is this Okay for stating point?)


I should take care saturation Current rating should twice.


Q2

How do we calculate L3? ( not necessary to change from PMP3672?)

PMP3672:

www.ti.com/.../slvr948.pdf

Thank you for your support

Best Regards

  • Kanji-san

    PMP3672 configures TPS92210 in an inverting buck topology.  TPS92210 is designed for an isolated flyback, so even though it's non-isolated this design still requires an optocoupler to operate.

    We recommend that they use one of our controllers specifically designed for this topology, such as TPS92075.  TPS92075 has an excel calculator for this buck topology http://www.ti.com/lit/zip/slvc463 

    If you find that TPS92075 does not meet your requirements, a list of all AC/DC LED driver controllers we have that work in this topology are available here http://www.ti.com/power-management/led-drivers/general-lighting-led-drivers/products.html#p207=AC/DC&p1129=Buck

    Best Regards,

    Eric

  • Dear Eric-san

    Thank you for your answer quickly!

    I understand that TPS92210 is isolated topology inherently.

    Thank you for introducing TPS92075.

    I will investigate  about that ,however, TPS92075 seems  no T8 tube reference design which is closely to our spec.

    If you answered  straightly to my questions below Q1,Q2 about changing PMP3672 L4,L5 and L3 values in case If were 800mA,

    its great help for us.

    Otherwise, I will investigate PMP4347 ,TPS92314 again.( But transformer should be bottle-neck.)

     ~~~~~~~~~~

    Q1
    How do we calculate L4,L5 if LED current increased ?

    (PMP3672(50V/0.35A default: 56uH + 56uH) If LED current was 800mA, it should be calculated as
    0.35/0.8 *56 = 24.5uH + 24.5uH?
    ( Is this Okay for stating point?)
    I should take care saturation Current rating should twice.


    Q2
    How do we calculate L3? ( not necessary to change from PMP3672?)

    ~~~~~~~~

    Thank you for your cooperation.

    Best Regards

  • Kanji-san

    The engineer that designed PMP3672 will answer your questions in the next few days.

    Eric

  • Hi Kanji-san,

    This was a design done when devices suited for buck operation were not available. As Eric suggested, we now have devices like TPS92075 more suited for buck operation.

    Your estimate of the required inductance is correct. If output voltage remains same, the inductance has an inverse relationship to current. However, the flux swing in the inductor is high, as the operation is in DCM. So you may have to use an inductor with sufficiently large Isat rating to reduce core losses.

    The value of L3 depends only on the bias current requirement. So it can remain same.

    Regards,

    Salil

  • Dear Salil-san

    Dear Gentlemen

    Thank you for your  support. I will talk with my customer.

    Thank you and with my best regards