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LM3478: Use boost converter for charging battery with BMS

Travis Duncan-Haynes
Prodigy 30 points
Part Number: LM3478

Tool/software:

Hello

I am designing a solar harvesting power supply with a Talentcell 6V 6Ah LiFePO4 Battery Pack. The battery has protection for over-charge, over discharge, over current and over temperature. If the battery is treated as open circuit for over-charge protection, would the LM3478 boost converter go into shutdown mode or continue running? If the LM3478 is still running, is it safe to operate under open/short circuit conditions? Can this charge controller be used for non-static loads?

The design will have a Vin of 4-5V and output 7V/2A.

Thank you for your help.

Travis

  • 0
    TI__Intellectual 2210 points

    Hi Travis,

    Thanks for reaching out via e2e. May I ask you what do you mean by open circuit for over voltage protection? Would that mean that you have no input for the LM3478? Also, by non-static load, are you referring to a variable output current?

    However, the LM3478 has a UVLO protection at the input, meaning that if the voltage drops below the UVLO threshold (2.85V) the device will shut-down.

    Kind regards,

    Federico

  • 0 in reply to Federico Galli
    Prodigy 30 points

    Hello Federico,

    Attached is a block diagram of the solar harvesting power supply. Solar Harvesting System

    Here are the responses to your questions:

    May I ask you what do you mean by open circuit for over voltage protection? I meant the battery would act as an open circuit during overcharging.

    Would that mean that you have no input for the LM3478? The input would be a solar panel with a MPPT to provide 5V to the LM3478.

    Also, by non-static load, are you referring to a variable output current? Apologies the load would be a battery, the datasheet is attached below.

    YB-LFP 6.4v 6Ah Spec (english).pdf

    I wanted to know if the LM3478 can still operate with an open circuit on the load if the BMS on the battery activates during overcharging.

    Let me know. Thanks.

  • 0 in reply to Travis Duncan-Haynes
    TI__Intellectual 2210 points

    Hi Travis,

    Thanks for the clarification, that helps. In no-load or light-load condition the device will still regulate the output voltage to the desired value. Hope this answers your question.

    Kind regards,

    Federico

  • 0 in reply to Federico Galli
    Prodigy 30 points

    Thank you for the clarity as well. Should I be concerned of any safety precautions for the LM3478 constantly running? I am planning to connect the voltage sensor parallel and a current sensor in series with the battery.

  • +1 in reply to Travis Duncan-Haynes
    TI__Intellectual 2210 points

    Hi Travis,

    Nothing specific, with a voltage sensor, a current sensor and the device voltage regulator it'll work more than fine.

    Kind regards,

    Federico