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Thread: Gate charge/discharge configration

  1. #1
    Beginner Beginner LiangXiao is on a distinguished road
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    Gate charge/discharge configration

    I used the BEMF demo code to drive my TLE9879 pcb . In the stage of open loop, the motor started and spun for short time, then stoped.Sometimes the motor had vibration.
    I added the gate charge current, the situation changed better,but the motor still stoped.
    What should I do, and what principles should be used to configure the gate charge/dischage current?

    Thanks!
    Last edited by LiangXiao; Oct 7th, 2019 at 07:54 AM.

  2. #2
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    Hi LingXiao,

    try decreasing the reference speed and adding a small load to the motor. This will will improve the performance of the closed loop.
    When this does not work or is not possible for your setup, you can try to set EMO_RUN to 0 in EMO_BEMF.h.
    This will keep the regulation in open loop.

    The configuration of the gate charge/discharge currents is highly depends which aspects of your application are critical.
    To get started, you first need to know the typical gate-drain charge QGD necessary to switch on your MOSFETs.
    You can usually find this in your MOSFETs Data Sheet in the typical gate charge graph:
    Click image for larger version

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    The charge/discharge current now mainly depends on your desired MOSFET switching time.
    Slow switching times will result in higher power dissipation and fast switching will result in higher EMI.

    The desired gate-dis/charge current can be calculated:
    Click image for larger version

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    But this is only a starting point, from there you can optimize your switching behavior, since the gate-charge deviates with production-spread, battery voltage and many other parameter.
    If you chose slow switching times you need to adapt the PWM dead-time or the bridge driver turn on/off delay to prevent cross conduction caused by the overlap of two MOSFETs in the half-bridge you are controlling over PWM.

    Best,
    Fiz
    The views expressed here are my personal opinions, have not been reviewed or authorized by Infineon and do not necessarily represent the views of Infineon.

  3. #3
    Beginner Beginner LiangXiao is on a distinguished road
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    Hi Fiz,
    Thank you for your advice.I use the BEMF sensorless demo code to drive my motor.In the Config Wizard,I don't konw the meaning of some parameters such as the Switch-on Speed in the picture below,and how to set these values in the picture to adapt my motor.
    Click image for larger version

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    Best!

  4. #4
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    Hi LingXiao,

    during the open loop the regulator will try to phase in the generated control pattern with the rotating motor.
    For this to work you need to give the regulator a starting speed and a desired end speed.
    During this start up phase the regulator will increase the Duty Cycle and compares the expected to the detected BEMF zero-crossing events.
    If you experience problems during the ramp-up you can increase the duration of the rotor alignment, this will give the regulator more time to phase in.
    Also try to chose end duty cycle and speed after the ramp up as close as possible to your desired application duty cycle and speed.

    Best,
    Fiz
    Last edited by Fiz; Oct 14th, 2019 at 12:06 AM.
    The views expressed here are my personal opinions, have not been reviewed or authorized by Infineon and do not necessarily represent the views of Infineon.

  5. #5
    Beginner Beginner LiangXiao is on a distinguished road
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    Hi Fiz,
    Thank you .But I still don't konw how to set the Swich-on speed.
    Best.

  6. #6
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    Hi LiangXiao,

    What motor are you using and what behavior does it show during the ramp-up?

    Best,
    Fiz
    The views expressed here are my personal opinions, have not been reviewed or authorized by Infineon and do not necessarily represent the views of Infineon.

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