• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 331 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.

BQ24800: Question for the behavior of Input Current Dynamic Power Management

Kazuki Kuramochi
Genius 10535 points
Part Number: BQ24800

Hello expert,

I have question for the behavior of Input Current Dynamic Power Management.

I'd like to know about the output voltage for system side.
I think output voltage for system side is maintaining Adapter voltage when the sum of system side current and Charging current is exceeded current limit. Is this correct?
After above situation, output voltage for system side would be same as battery voltage when system side charging current is exceed  current limit. Also, External bat FET(Q1,Q2) is regulating AC adapter voltage to battery voltage. Is this correct?

This question is from I'm worrying about heat-up of BAT FET when system current is exceeded current limit.


Best regards,
Kazuki Kuramochi

  • 0
    TI__Mastermind 33335 points

    The system voltage is the same as the adapter voltage when the AC adapter is connected. 

    "The total input current, from a wall adapter or other DC source, is the sum of the system current and current required to charge the battery. When the input current exceeds the set input current limit, the BQ24800 device decreases the charge current to provide priority to the system load. As the system current rises, the available
    charge current drops to 0. If the system load increases further after charging current has been reduced to 0, the charger goes into hybrid power boost mode and adds battery power to support the system load, maintaining the input current limit."

    When adapter is removed, the system is connected to battery through BATFET.

    Regarding your questions,

    I think output voltage for system side is maintaining Adapter voltage when the sum of system side current and Charging current is exceeded current limit. Is this correct? Answer: Correct
    After above situation, output voltage for system side would be same as battery voltage when system side charging current is exceed  current limit. Also, External bat FET(Q1,Q2) is regulating AC adapter voltage to battery voltage. Is this correct? Answer: Incorrect. System voltage is still equal to the adapter voltage. BATFET is off. 

  • 0 in reply to Tiger Zhou
    TI__Genius 10535 points

    Hi  Tiger,

    Thank you for your explanation and sorry for my late reply.
    I probably understood what is happened under Hybrid Power Boost Mode that is boosting battery voltage for system side load.
    Then, I'd like to know about how to measure AC side voltage and the accuracy of boosted voltage from battery side.

    Would you explain it?


    Best regards,
    Kazuki kuramochi

  • 0 in reply to Kazuki Kuramochi
    TI__Mastermind 33335 points

    During hybrid power boost mode the adapter current is regulated at input current limit level so that adapter will not crash. We don't measure the AC side voltage. 

  • 0 in reply to Tiger Zhou
    TI__Genius 10535 points

    Under hybrid power boost mode, battery side voltage is boosted by Q4 and Q5 for supply power for system load side as far as my understanding.
    They this rail must need to same voltage as AC side voltage.
    Then, I think BQ24800 need to monitor AC side voltage for achieving same boosted voltage from battery side.

    Would you tell me BQ24800's method of decided boosted voltage?
    Also, is there any current limit on battery side under hybrid power boost mode?


    Best regards,
    Kazuki Kuramochi

  • 0 in reply to Kazuki Kuramochi
    TI__Mastermind 33335 points

    Hi, Kazuki,

    In hybrid power boost mode, instead of control the boosted voltage, we control the current. The adapter current is regulated at input current limit level so that adapter will not crash. 

    To keep the discharge current below battery OCP rating during hybrid boost mode or battery only boost mode, the BQ24800 device supports discharge current regulation.