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Thread: Vb pin voltage drops when using IR2184

  1. #1
    New Member New Member Georgiy_Klimov is on a distinguished road
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    Jan 2021

    Vb pin voltage drops when using IR2184

    Hello, dear collegues! I'm currently designing H-bridge converter for DC-motor drive.

    I decided to use bootstrap driver for driving converter MOSFETs. IRF8721PBF were choosen as switches, IR2184 was chosen as a gate driver.
    To quickly test their performance I soldered bread board with Half-bridge converter. You can see the circuitry on the figure. There is also decoupling capacitors on inputs of L7815 and IR2184, and on Vcc pin of IR2184
    Click image for larger version

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    The problem is the gate voltage drop on upper switch during switching on or it better to say oscilation on upper switch gate.
    The oscillograms was pictured and you can see voltages on load, on upper and lower gates, and on Vboot and Vcc pins of IR2184.
    Click image for larger version

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    I have tried different valiues of Cboot from 6.8nF to 1uF but there is no significant difference between results.

    It would be great to get any suggestions concerning the problem.

    ?????? ?????? osc3.gif‎  

  2. #2
    Infineon Employee
    Infineon Employee
    Srivatsa is on a distinguished road
    Join Date
    Apr 2018
    You try with a bulk capacitor of around 10 uF at the Vcc pin. This should make sure the 1A current limit of LM7815 is not tripped when the driver is switching the MOSFETs.

    Make sure the 10 uF capacitor is placed closed to the driver IC.
    More information can be found under
    Please contact our Technical Assistance Center for further inquiries

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