• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 63 subscribers
  • Views 313 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

TPS92314A: non_isolated for T8 tube

KANJI SHIBATANI
Mastermind 6205 points
Part Number: TPS92314A
Other Parts Discussed in Thread: PMP4347, PMP4362, PMP8007, TPS92314, TPS92210

Hello

I found that TI has 4 reference designs for T8 tube with TPS92314A.

For universal ( AC85-265) design, PMP4347 seems good reference, but

do you have non-isolated reference design with universal( AC85-265) , T8 tube?

Is there any technical difficulty for universal with non-isolated? ( I am sorry such a fundamental question).

Customer think to  transformer height is key for T8 tube.

PMP4347 AC85-265V isolated

PMP4362 AC198-264V isolated

PMP8449 AC250-305V isolated

PMP8007 AC198-26V4 non-isolated

Best Regards

  • 0
    TI__Mastermind 28655 points

    Hello Kanji,

    An isolated buck-boost will place the output voltage on top of the rectified AC, is this okay for them?  It can make the working voltage of the design higher which can affect safety requirements.

    There are also buck designs that can work however the THD will probably be high at the lower AC input voltages.  This can be made better by lowering the LED stack voltage.  See PMP3672 for an example.

    The designs that you looked at are high voltage designs.  To make these work for universal voltage the transformer/inductor would need to be larger.  The trick with these designs is the transformer/inductor.  One of buck-boost designs uses two EFD15 inductors in series to get enough energy storage for the design and it is still high voltage only.  It, mostly like, will not be able to work at 85 VAC input.  Either the flyback or buck-boost have to store energy to transfer to the load, this is what determines the size of the transformer/inductor.

    For isolated, do they want primary side regulated (no opto-coupler feedback)?

    For non-isolated, do they want the buck-boost topology only?

    The PMP4347 design could be modified to be a buck-boost.  It would require a new transformer/inductor design as well as other changes.

    How important is efficiency?  One reason for this question is the VCC for the TPS92314 can be generated from a linear circuit from rectified AC.  At high line the MOSFET generating this would need to dissipate up to 700 mW.

    Best Regards,

  • 0 in reply to Irwin Nederbragt
    Mastermind 6205 points

    Dear Irwin-san

    Thank you for your answer precisely and  so quickly.

    I had talked with customer today. Customer feels PMP3672 looks fine because which is non-isolated/ almost same spec for theirs .

    Using TPS92210 photo coupler should be fine because PCB length is enough (300 mm).


    In fact, customer says they cannot find any 3rd party who can make 8mm-height custom-transfomer, so, they prefer non-isolated .


    customer's spec is

    Vin   85-230V for Japan 100/200V
    Vout 70V ( 2.4V * 28 series =67.2V)
    Iout  400mA
    THD TBD ( Japan Harmonic regulation for LED lighting is changed at 2019 , but 25% should be worst) .
    size  30mm x 18mm x 8mm for T8 tube

    Customer want to know how to change L1~L5 and other parts values in PMP3672 for their spec .

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

    Anyway, I had downloaded sluc242 for TPS92210EVM Design Tool 11.01.26.

    However, I did not find "non-isolated " work sheet in it. ( Its PFC flyback ( isolated ) topology.)

    Would you please let us know how to change the values in PMP3672?

    Thank you for your cooperation


    Best Regards

  • 0 in reply to KANJI SHIBATANI
    TI__Mastermind 28655 points

    Hello Kanji,

    To keep the THD lower the LED string voltage for this topology needs to be lower.  The LED string is in series with the rectified AC so current cannot flow to the LEDs until the rectified AC voltage goes above the LED stack voltage.  67.2V at 400 mA is 26.9W, is this correct?  The power level of PMP3672 is 15W.

    Let me know what they can do for the LED stack voltage since 67.2V will have higher THD than PMP3672.

    Best Regards,

  • 0 in reply to Irwin Nederbragt
    Mastermind 6205 points

    Dear Irwin-san

    Thank you for your comment  promptly.

    Yes, customer's spec is  67.2V x 400mA=26.9W

    But  I understand that  to lower THD is very tough for high LED voltage from your advice.

    I will discuss with customer with their spec again.

    Thank you again