• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 737 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

BQ24650: Adapter current limiting with MPPT?

Edward Caceres
Prodigy 50 points
Part Number: BQ24650
Other Parts Discussed in Thread: INA138, BQ24630

The BQ24650 has nearly all the features I need in a standalone charger that can be configured for SLA or LiFePO4 batteries (nominally 12V). So far, so good...

The one feature I'd like to add is adapter current limiting. There must be a clever way or measuring adapter current (using an INA138 or similar?) and using the output voltage (from the INA138) to modulate the MPPT set-point accordingly.

The reason for this is typical: The AC/DC adapter, when plugged in, would supply power to the system logic and also the charger. Powering the system logic is a priority, whereas the charger can be scaled down to use only the remaining capacity from the adapter. I cannot depend on "input voltage droop" in this application.

Suggestions?

  • 0
    TI__Mastermind 20570 points

    The bq25650 does not have power path control.

    Where are you connecting the system logic? If you connect the system in parallel with the battery, then your system logic will be able to draw current from the adapter while the battery can be charged with the remaining adapter power.

    The down side is once battery charging is terminated, the system load will start discharging the battery. Once the battery is below re-charge threshold, battery charging re-starts.

  • 0 in reply to Jing Zou
    Prodigy 50 points
    The power-path would be accomplished with either simple diodes, or possibly "ideal diodes" made with appropriate FETs.
    When the AC/DC adapter is plugged-in, the battery will be fully isolated from the system load.
    The power-patch solution is relatively easy. It's the adapter current limiting that I need to solve first.
  • 0 in reply to Edward Caceres
    TI__Mastermind 20570 points
    The bq24650 were designed targeting solar charging applications where current capability of the solar panel under different lights varies. Thus there is no input current limit feature build in with the bq24650. For LiFePO4 battery charging, you may want to consider using bq24630.