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TPS92314A: please advise for T8 tube design

KANJI SHIBATANI
Mastermind 6205 points
Part Number: TPS92314A
Other Parts Discussed in Thread: TPS92314

Hello


My customer intend to choose TPS92314 for next T8 tube project.

*Vin AC 85 ~265V

*Vout=70V
;VF＝2.4V x 28pcs => VF＝67.2V

*T8 size 280 mmx 18mmx 8mm　( therefore, PMP4347

seems to be good for our reference.)

Q1

Customer want to calculate for VF＝2.4V x 28pcs => VF＝67.2.

However, for sluc446 Calculation_tools , 10 LED seems

maximum for isolated scheme. ( for non-isolated, its okay)

How do we do for calculation when number of LED exceed 10

for isolated ? ( please see attached )


Q2

For the new project, height of parts  is very critical (8mm).

Would you please provide  data sheet ECR28 Transformer, 460uH

(BOCHANG) in the PMP4347 BOM  "T1 " below?  or send me data sheet link for this?... I can not find from internet.


BOM
www.ti.com/.../slur984.pdf

Best Regards

  • 0
    TI__Mastermind 28655 points

    Hello Kanji,

    In an isolated primary side regulated design the controller doesn't know what the output voltage is so I would just use 10 LEDs in the tool and change the transformer ratio from what the calculations show.  Other parts will have to scale as well (diode reverse voltage, output capacitor rating, etc).  If you use the PMP4347 as a start for the design you can scale the values of that design to get close.

    Example for design tool:  Vf = 2.4V x 28 = 67.2V.  Calculator is 3V x 10 = 30V.  ratio is 67.2/30 = 2.24 multiplier for secondary turns (round appropriately).  The current will be 30/67.2 * tool calculated current.  If it is 18W output, current would be 600 mA, ratio current would be 30/67.2 * 600 mA = 268 mA.

    I asked about the transformer to a colleague and he found a drawing that shows it to be at least 9.6 mm tall.  The output capacitors C11 and C12 are 10 mm so this design is taller than 8 mm.

    If you are interested in the transformer drawing I can send what was found.

    Best Regards,

  • 0 in reply to Irwin Nederbragt
    Mastermind 6205 points

    Dear Irwin san

    Thank you for your quick support.  Its well you answered in detail. 

    I will study it.

    Best Regards