Dec 14, 2019
05:50 PM
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Dec 14, 2019
05:50 PM
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
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
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Jun 15, 2020
08:28 AM
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Jun 15, 2020
08:28 AM
9 Replies
Dec 16, 2019
11:39 AM
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Dec 16, 2019
11:39 AM
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
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
Dec 16, 2019
11:44 AM
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Dec 16, 2019
11:44 AM
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
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
Dec 18, 2019
11:34 PM
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Dec 18, 2019
11:34 PM
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
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
Dec 19, 2019
10:36 AM
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Dec 19, 2019
10:36 AM
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
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
Dec 19, 2019
11:50 AM
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Dec 19, 2019
11:50 AM
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
Yes, they're related topics. It appears that, based on this, we're going to have to look at a different approach.
Thanks,
Scott
Jan 26, 2020
05:39 AM
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Jan 26, 2020
05:39 AM
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/Infineon-HV_Floating_MOS_Gate_Drivers-ApplicationNotes-v01_00-EN.pdf?f... Chapter 8 addresses your issue a bit differently.
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/Infineon-HV_Floating_MOS_Gate_Drivers-ApplicationNotes-v01_00-EN.pdf?f... Chapter 8 addresses your issue a bit differently.
Jan 27, 2020
08:58 AM
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Jan 27, 2020
08:58 AM
If I recall correctly, I calculated a much larger capacitor was needed. I will review the app note, however.
Thanks,
Scott
Thanks,
Scott
Jun 14, 2020
01:44 PM
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Jun 14, 2020
01:44 PM
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.
Use a 1W DC-DC, they are just 5x10mm and solve your problem for good.
Jun 15, 2020
08:28 AM
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Jun 15, 2020
08:28 AM
We decided to use a relay instead -- working fine so far.