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Thread: IRS2007/2008 -- drive with DC control input?

  1. #1
    New Member New Member brencon is on a distinguished road
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    IRS2007/2008 -- drive with DC control input?

    Hello,

    Can half-bridge gate drivers like the IRS2007 and IRS2008 be controlled by DC voltages at the IN pin, or is there a minimum input frequency? The datasheet doesn't specify this. We are not using PWM, but rather just want to turn on either the high-side or the low-side driver for long periods of time.

    Thanks,
    Scott

  2. #2
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    Hi,

    The IRS2007 and IRS2008 do not have a minimum input frequency requirement. If the high-side power supply is sufficiently charged or an external isolated power supply is used to power the high side, these drivers can be controlled by DC voltages.

    Regards,

    Srivatsa
    More information can be found under www.infineon.com/gatedriver
    Please contact our Technical Assistance Center for further inquiries

  3. #3
    New Member New Member brencon is on a distinguished road
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    Hi Srivatsa,

    Thank you for the quick response. I'm a little unclear on some of what you said, so I want to try to clarify.

    What did you mean when you referred to the high-side power supply being "sufficiently charged"?

    FYI, our high-side supply is not isolated. It is 48 V, referenced to the same ground as our logic signals.

    Thanks again,
    Scott

  4. #4
    New Member New Member brencon is on a distinguished road
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    Half-bridge gate drive for indefinite switching?

    Hello,

    I'm concerned that perhaps I'm missing something in my thinking. I'm new to using half-bridge gate drivers which rely on bootstrapping to drive the high-side device. We need switch on the appropriate device in the bridge and leave it on for a long duration, perhaps as much as an hour. It appears that the bootstrap approach doesn't allow this unless the capacitor is enormous, to prevent the gate drive voltage from gradually dropping as time goes on.

    Am I thinking about this correctly? The part we're considering using is the IRS2008.

    Thanks,
    Scott

  5. #5
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    Hi Scott,

    I merged both the queries as they may be related to the same topic.

    Yes, that is what I meant by high-side power supply being sufficiently charged. To remain "ON" for a long duration the high-side power supply must deliver the required power. If the bootstrap capacitor does not have a chance to recharge, then over time it drains out pulling the high-side output low.
    One option is to use an isolated power supply to power VB instead of bootstrapping it.

    Thanks and regards,

    Srivatsa
    More information can be found under www.infineon.com/gatedriver
    Please contact our Technical Assistance Center for further inquiries

  6. #6
    New Member New Member brencon is on a distinguished road
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    Hi Srivatsa,
    Yes, they're related topics. It appears that, based on this, we're going to have to look at a different approach.
    Thanks,
    Scott

  7. #7
    Beginner Beginner sujoy is on a distinguished road
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    Hi Brencon,

    If the gate has to be on for an hour or so, why don't you use a huge capacitor like 100uF or so? I think it should do the trick. You may need to add a resistor between the bootstrap diode and Vcc to limit current surges though.

    Also you can check out this application note, https://www.infineon.com/dgdl/Infine...6c47de609d140a Chapter 8 addresses your issue a bit differently.

  8. #8
    New Member New Member brencon is on a distinguished road
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    If I recall correctly, I calculated a much larger capacitor was needed. I will review the app note, however.
    Thanks,
    Scott

  9. #9
    Beginner Beginner Holmer is on a distinguished road
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    High side Iq is 75µA max, or 270mC per hour. so a cap of 270000µF will droop one Volt. Good luck recharging that...
    Use a 1W DC-DC, they are just 5x10mm and solve your problem for good.

  10. #10
    New Member New Member brencon is on a distinguished road
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    We decided to use a relay instead -- working fine so far.

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