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BQ79631-Q1: Contactor driver with BQ79631-Q1

Fatih TAHTASAKAL
Prodigy 25 points
Part Number: BQ79631-Q1

Hello 


In the BESS system operating at 1500V that I am working on, I want to control the contactors with the BQ79631-Q1.
I will design a driver circuit to drive the contactors. However, how should this driver circuit receive the trigger signal?

I don't think BQ79631-Q1 digital GPIO outputs are sufficient to handle all scenarios. I also think there might be issues with error messages in SPI communication.
Is it necessary to design a contactor driver using an MCU and communicate via SPI?

Is the design in the following basic-level schematic suitable for contactor driver? Or is there a better solution?



Is there a reference schematic for driving contactors with the BQ79631-Q1?

Best Regards
Fatih TAHTASAKAL

  • 0
    TI__Expert 4200 points

    Faith,

    All I can do for you is tell you about the SPI master capabilities of the BQ79631 (found in section 8.3.5.1.7 of the datasheet) and that we do not have reference schematics beyond what is in the EVM User's Guide. This post seems to be mostly asking about the "Contactor Driver" you are referencing, which appears to be something you are designing yourself and therefore I cannot really help you with it. 

    If you have specific questions about the BQ79631, feel free to ask them. 

    Regards,

    Ben

  • 0 in reply to Benjamin Luty
    Prodigy 25 points

    Hello Ben

    First of all, thank you for your response. I am just curious about one thing: What is the easiest way to control contactors with the BQ79631-Q1?

    Is there an easier method without using SPI communication?

    Best regards

    Fatih

  • 0 in reply to Fatih TAHTASAKAL
    TI__Expert 4200 points

    Faith,

    There are only two options if you want to communicate from the BQ79631 to a periphery device: the SPI master feature and the GPIO pins. The GPIO pins are only changed when the MCU sends a command to change them and can only really be used as a toggle. The SPI master, on the other hand, can send and receive SPI communication. I do not know what communication needs to be done to control contactors, so I cannot say what would be "easiest".

    Regards,

    Ben

  • 0 in reply to Benjamin Luty
    Prodigy 25 points

    Hello Ben

    Thank you for your response.

    Option 1) SPI communication is very sensitive and can result in erroneous messages. In the event of an erroneous message, the on-off duration of the contactors will increase. Therefore, I am concerned.

    Option 2) There is a BQ79600 bridge between the BQ79631-Q1 and the MCU. To activate the BQ79631-Q1 GPIO pin, the MCU will send data to the BQ79600, and the BQ79600 will send data to the BQ79631. As a result, the process will take a long time. Therefore, I am concerned.

    I am curious about the method TI used in their testing phases. Which method did TI prefer when working with the contactor? What are the turn off time in the short-circuit protection during TI tests? Is there a document available about the contactor driver used in TI tests?

    Any support you can provide is very valuable to me. Thank you.

    Best Regards

    Fatih

  • +1 in reply to Fatih TAHTASAKAL
    TI__Mastermind 34780 points

    Hello Faith,

    This type of contactor testing is not done by TI, so we do not have such data. The best way in my opinion would be to use SPI to get the data, I don't recall hearing there being much errors here. The AFE should likely be close to MCU.

    The device's fastest detection for over-current protections is ~32-us.

    Best Regards,

    Luis Hernandez Salomon