• State
  • Locked Locked
  • Replies 5 replies
  • Subscribers 63 subscribers
  • Views 1039 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.

BQ25504 AC energy

Darius Baronas
Intellectual 260 points
Other Parts Discussed in Thread: BQ25504, BQ25505

Hi all ! I'm doing autonomous "thing" that should work from electromagnetic energy and send signals via low power RF module. So...As i understand BQ25504 do not have internal rectifier, so i need to use external schottkey full wave bridge and capacitor for VIN_DC input ? Another thing..solar cell have mpp at 80%, but how it is with induced voltage and current in the coil ? Should i use MPPT or not ? Can't find information about it..And can i use small li-ion battery and supercap as buffer? thanks !  

  • 0
    TI__Mastermind 20570 points

    Regarding 1, if an AC source like piezo-electrical is used, you will need a rectifier composed of very low forward voltage drop and low reverse leakage current diodes.

    Regarding 2, asume you are referring to the boost inductor. The induced voltage will be the difference of 80% of the open circuit voltage and VSTOR voltage.

    Regarding 3, I am not sure what do you mean by using battery and supercap as buffer. The bq25504 is designed to work with storage element attached to VBAT with at least 100uF of equivalent capacitance.

     

  • 0 in reply to Jing Zou
    Intellectual 260 points
    Yes, i just tried schottkey with low forward voltage drop, it works fine. But i will use not solar cell (which IV curve MPP is 80% Voc voltage) , i will use electromagnetic generator, and i want to charge battery as fast as possible. Should i use mppt technique here, i lets say i have 1V rectified DC voltage from electromagnetic generator ?
  • 0 in reply to Darius Baronas
    TI__Mastermind 20570 points
    MPPT is implemented in order to maximize the power extracted from an energy harvester source. The boost converter indirectly modulates the input impedance of the main boost charger by regulating the charger's input voltage. I am not familiar with electromagnetic generator. For high impedance energy sources, it is recommended to use the MPPT to prevent the input voltage from crashing. The peak current flowing into boost converter is 200 mA typical. If the energy source is able to provide 200mA current for the boost converter, than you may not need the MPPT function enabled.
  • 0 in reply to Jing Zou
    Intellectual 260 points

    There are way connect two batteries (primary and secondary) like in bq25505 chip ? 

  • 0 in reply to Darius Baronas
    TI__Mastermind 20570 points
    The scheme of the primary and secondary storage elements is essentially two push-pull multiplexer drivers intended to mulitplex between a primary nonrechargeable connected at VBAT_PRI and secondary storage element connected on VBAT_SEC based on the VBAT_OK signal. Therefore, it is possible to build an external circuitry to achieve this. Please refer to datasheet page 12 Push-Pull Multiplexer Driver for detailed operation. However, to drive the VBAT_OK and the inverted signal switch at the correct timing and making sure the two signals are not on at the same time is challenging.