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TPS63802: Current-Feedback buck-boost converter

Dave Young
Intellectual 520 points
Part Number: TPS63802

Hi There-

I'm working on a circuit which can charge a 1-cell LiIon battery (2.5-4.2V) from a primary battery (configuration TBD, ranging from 0.8V - 3.8V). I'm planning on using a buck-boost TPS63802 as the power converter. Instead of being a voltage-regulated output, I would like to have the circuit be current-regulated to deliver 150mA of current whenever enabled.

I have designed a current-sense resistor (R28) which is amplified by a non-inverting op amp (U7) to deliver a feedback signal to the TPS63802 (U6). The parts are on the way for prototyping. But I was hoping someone would have some time to review the attached schematic. I'm particularly concerned about the control system and making sure everything is stable.

Thanks so much!

  • 0
    TI__Expert 7925 points

    Hi Dave,

    Thanks for reaching out. 

    In principle this should work as a constant current source. I would suggest reducing C?, to 10n or so, and make sure your opamp inputs can go down to ground. However...

    I strongly recommend using a proper battery charger IC for several reasons:

    1. A charger IC will terminate the charging precisely at 4.2 V. In the above circuit there is no voltage limiting. You will overcharge and damage the battery, and most likely something or someone else as well.
    2. A charger IC performs a proper CC/CV charging, with a precharge cycle if the battery is empty. Charging an empty battery with the nominal charge current can damage the battery.
    3. A charger IC will have some additional safety features, such as a charge timer, input for temperature measurement etc.

    Best regards,
    Milos

  • 0
    TI__Expert 7925 points

    Hi Dave,

    We haven’t heard back so we're assuming this answers your question. If not, just post a reply below, or create a new thread if the thread has locked due to time-out.

    Thanks and regards,
    Milos

  • 0 in reply to Milos
    Intellectual 520 points

    Yes, this is great! I just got parts in yesterday that allowed me to test that it worked. I had to add more output capacitance to smooth the current ripple though.

    Those are excellent suggestions on the control of the charge profile. I will be sure to implement them in our control system.

    Thanks!