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TPS55340: Constant current charging with SEPIC

Dice-K
Mastermind 7460 points
Part Number: TPS55340
Other Parts Discussed in Thread: PMP10081, TPS40210, TLC272

Hi support team,

I want to trickle charge Ni-Cd battery with SEPIC of TPS55340.
Is it possible to realize a constant current circuit with the attached configuration?
The output current information is fed back to the FB pin.

TPS55340_CC.pdf

Vin: 24V
Vout: 30V or less
Charging current: 200mA or 120mA

Regards,
Dice-K

  • 0
    TI__Genius 11215 points

    Hello, 

    Thanks for reaching out. We have some reference designs available for SEPIC battery charger, at this link for example you can find one (schematic included) https://www.ti.com/tool/PMP10081 
    This example is using another device, but it shows you how to realize the two loops, one for constant voltage and one for constant current. Let me know if further help is needed. 

    Kind regards,

    EM

  • 0 in reply to EM
    Mastermind 7460 points

    Hi EM,
    Thank you for your reply.

    Is constant voltage and constant current feasible with the circuit below?

    Best regards,
    Dice-K

  • 0 in reply to Dice-K
    TI__Genius 11215 points

    Hello Dice-K, 

    This circuit can work in principle, but I would not recommend it because the performance might not be very good. The bipolar transistor and in particular its Vbe is dependent on temperature and this might affect the performance of your circuit. 

    Kind regards,

    EM

  • 0 in reply to EM
    Mastermind 7460 points

    Hi EM,
    Thank you for your support.

    I realized that it would be difficult to achieve with the circuit I attached.
    You introduced PMP10081. Is a similar circuit feasible with TPS55340?
    It seems that ISNS of TPS40210 realizes constant current.
    I can't find the equivalent pin for ISNS on TPS55340.

    Best regards,
    Dice-K

  • 0 in reply to Dice-K
    Mastermind 7460 points

    Hi EM,
    I'm sorry, I have misunderstood.

    It seems that a constant current circuit is realized using TLC272.
    Is this constant current circuit using TLC272 applicable to SEPIC of TPS55340?

    Best regards,
    Dice-K

  • 0 in reply to Dice-K
    Mastermind 7460 points

    Hi EM,
    Excuse me often.

    Could you please comment on whether the constant current and constant voltage circuit using with TLC272 can be applied to the SEPIC of TPS55340?

    I'm sorry if you have already answered.

    Best regards,
    Dice-K

  • 0 in reply to Dice-K
    TI__Genius 11215 points

    Hello, 

    Thank you for your patience. Let me share with you my answers: TPS55340 has an integrated switch and therefore a fixed current limit, but I see no issue in designing a SEPIC with a converter instead of a controller. About the TLC272:  this opamp is also fine for such a design. Sorry for the delay in the answer, please let me know if you need further help. 

    Kind regards,
    EM

  • 0 in reply to EM
    Mastermind 7460 points

    Hi EM,
    Thank you for your help.

    I have a question about the text below.
    "I see no issue in designing a SEPIC with a controller instead of a converter."


    Does controller mean TPS40210 and converter mean TPS55340?
    If so, is the following sentence correct?
    "I see no issue in designing a SEPIC with a "converter" instead of a "controller "."

    If so, it can be interpreted that TLC272 can be used for SEPIC of TPS55340.

    Best regards,
    Dice-K

  • +1 in reply to Dice-K
    TI__Genius 11215 points

    Hello Dice-K, 

    Thank you so much for your reply, I just corrected the mistake in the message above: you are right, a controller is a device with an external FET, while a converter has an integrated FET inside the device. Yes, you are right, you can use the TLC272 for TPS55340 SEPIC configuration. Thanks again for your great feedbacks! Let me know if further assistance is needed. Have a nice weekend. 

    Kind regards,
    EM