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Topic: Diodo flyback in car (Read 440 times) previous topic - next topic

TomGeorge

Want to hear Tom's explanation of that!
The resistor from my experience is not just a current limit to the gate capacitance, but  protection for the opto-transistor if the MOSFET fails.
From work/repair experience, no resistor in the gate usually blows the cr&*p out of the driver circuit when the MOSFET goes bang!!!!.
The resistor usually protects the driver.
But feel free to leave it out, its just a personal preference.
Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

Paul__B

Interesting, but the MOSFET is probably the most expensive component, so it it fails, collateral damage to the opto-coupler is a relatively minor detail.  In fact, that is really the purpose of the opto-coupler, an expendable isolation of the two sections.

Certainly, in SMPS, you expect more widespread damage if the FET has failed.  Not fun things to attempt to repair.

I thought you might be wanting to limit the gate charging current from the opto-coupler.

RcP

Is the current that passes through the source and drain necessary to clean it from any noise or something? Or are the mosfets ready for the current to pass from source to drain without being clean?

Paul__B

Sorry, that's not making any sense.

As long as you do not attempt to pass more than the rated current through the FET (source - drain), do not expose it to any voltage in excess of the various ratings between elements, and do not allow it to overheat, it will function according to its specifications.

RcP

Perfect thanks for everything!

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