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OverUnity Research > Electrical / Electronic Theory and Learning Center > Learning Center Miscellaneous > MOSFET driver issue
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img  Grumpy
MOSFET driver issue « on: 2022-09-11, 01:20:20 »

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I'm using an IXDF604PI (see attached) MOSFET driver to drive a IXTH02N450HV (see attached) MOSFET.

Low-side driving, 130k resistor at voltage source.

I apply 300vdc.  I can measure 300vdc at the MOSFET.

When I apply power to the driver, the 300vdc  voltage drops to about 10vdc.  I don't see a signal at the gate when this happens.

This is even with the driver input connected to a signal generator or disconnected (floating).

10 k-ohm  resistor gate to source, 100 ohm resistor between driver and gate.

When the driver is turned off, the voltage returns to 300vdc.

What could be wrong?
   
img  Grumpy
Re: MOSFET driver issue « Reply #1 on: 2022-09-11, 01:55:57 »

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I'm using a AHV12V4KV2R5MAW power supply, and 6 of the drivers (6 channels).

Now, I'm thinking my 12v power supply is too low of current since only 1A. A single driver worked fine when I tested it a couple of weeks ago.
   
img  Hakasays
Re: MOSFET driver issue « Reply #2 on: 2022-09-11, 05:51:32 »

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Do you have the driver input side biased to ground as well?   I've had gate drivers that needed to be clamped with a 10-100k ohm pulldown resistor.


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"An overly-skeptical scientist might hastily conclude by scooping and analyzing a thousand buckets of ocean water that the ocean has no fish in it."
   
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Re: MOSFET driver issue « Reply #3 on: 2022-09-11, 06:44:53 »

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Quote from: Hakasays on 2022-09-11, 05:51:32
Do you have the driver input side biased to ground as well?   I've had gate drivers that needed to be clamped with a 10-100k ohm pulldown resistor.

Will try tomorrow.
   
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Re: MOSFET driver issue « Reply #4 on: 2022-09-12, 00:02:20 »

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Quote from: Hakasays on 2022-09-11, 05:51:32
Do you have the driver input side biased to ground as well?   I've had gate drivers that needed to be clamped with a 10-100k ohm pulldown resistor.

Thanks Hakasays!
This was the issue.  10k at the input to ground and it shuts off when floating.  They could have mentioned this in the datasheet...

Funny thing is that I had a 10k at the input when I tested it and then forgot the 10k at the gate, so I moved it.
   
img  Hakasays
Re: MOSFET driver issue « Reply #5 on: 2022-09-12, 02:37:27 »

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Quote from: Grumpy on 2022-09-12, 00:02:20
Thanks Hakasays!
This was the issue.  10k at the input to ground and it shuts off when floating.  They could have mentioned this in the datasheet...

Funny thing is that I had a 10k at the input when I tested it and then forgot the 10k at the gate, so I moved it.

The gate capacitance is so low and those drivers are such high impedance that it probably charges capacitively from its own drive voltage.
Glad to help ;)


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Re: MOSFET driver issue « Reply #6 on: 2022-09-12, 15:00:57 »

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Quote from: Hakasays on 2022-09-12, 02:37:27
The gate capacitance is so low and those drivers are such high impedance that it probably charges capacitively from its own drive voltage.
Glad to help ;)

I believe you are correct.  You can see the voltage bleeding off (from 12v down to zero) when you connect the resistor to the input.

I wanted to use a very fast TI driver but only a few were available and long lead time.
   
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Re: MOSFET driver issue « Reply #7 on: 2022-09-13, 03:09:36 »

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10k wasn't always working reliably so I Googled it:

Found out how to calculate the minimum resistance here:

https://electronics.stackexchange.com/questions/60427/calculating-the-pulldown-resistance-for-a-given-mosfets-gate

I'm betting it will be pretty low ohms.
   
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