• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 123 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: Multiple Solar Panels in Parallel at Input

David Morvay
Prodigy 10 points
Part Number: BQ24650

Tool/software:

Hello, 

I am working on a design with BQ24650 and had a few questions about the device. First, if I have multiple solar panels in parallel, how should I properly construct the input filter? Should I have an RC damping filter and reverse voltage protection diode for each of the solar panels or is one RC damping filter and diode for the entire system sufficient? If the former, I would assume the top resistor of the MPPSET circuit should be connected at the cathode of the diodes in parallel? My design requires three solar panels in parallel, so I currently have an RC filter and diode per panel. 

I am more than happy to share my schematics via email to get additional feedback on my entire design. I appreciate your help in advance!

  • +1
    TI__Mastermind 31816 points

    Hello David,

    Thanks for your detailed question.

     

    When using multiple solar panels in parallel with the BQ24650, here are a few recommendations:

    • It is good practice to place a reverse voltage protection diode and RC damping filter on each panel individually, especially if the panels are separated by some distance or might operate at slightly different voltages (due to shading or mismatch).
    • This setup prevents reverse current from flowing between panels.
    • If you were to use only one central filter/diode, the risk is that current could backfeed from one panel into another during uneven illumination
    • Your current approach, RC filter + diode per panel, is recommended and robust, particularly for three-panel configurations.
    • The resistor should be referenced after the protection diodes, ideally at the common cathode point of the diodes, where the combined current flows into the BQ24650 input. This ensures that the measure voltage reflects the actual panel voltage seen by the charger.

    Best Regards,

    Christian

  • 0 in reply to Christian Moyer
    Prodigy 10 points

    Hi Christian, 

    Great, I appreciate your answer! This leads me to another question: Looking at the schematic for the BQ24650EVM-639 evaluation module, there is a diode D3 that connects VOUT to VSYS. If a designed my system with a diode from VOUT to VSYS and had the MPPSET resistors referenced at the common cathode point of the diodes, MPPSET would always read VOUT when the solar panels are not conducting, correct? How would I handle this? It seems like this would create an unexpected state. 

  • 0 in reply to David Morvay
    TI__Mastermind 31816 points

    Hello David,

    The voltage seen on MPPT when adapter is not present, should be below the MPPT set threshold, since this is a buck-only charger. I don't see any obvious issue with VOUT being seen on MPPSET pin during this state.

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 10 points

    Hi Christian, 

    I see, this makes sense. So, looking at the data sheet, would the device enter this mode? - "If the MPPSET pin voltage is forced below 1.2 V, the BQ24650 stays in the input voltage regulation loop while the output current is zero." Hence, the BQ24650 would remain always on in this case as long as a battery is connected? Are there any disadvantages of this other than some continuous power draw from the IC? 

  • 0 in reply to David Morvay
    TI__Mastermind 31816 points

    Hello David,

    David Morvay said:
    Are there any disadvantages of this other than some continuous power draw from the IC?

    This should be the only disavantage. 

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 10 points

    Thank you, Christian! I appreciate your feedback!