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Mosfet gate driver current calculation

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h@ro

Junior Member level 2
In order to calculate the gate current for driving the gate of a MOSFET by PWM at ~40Khz, I use the formula for peak current "Ip" located on the 4th page of the publication "http://www.ti.com/lit/an/slua054/slua054.pdf"

My question is what is a systematic way of calculating Ton term in that formula? A smaller Ton results in lower switching loss, but requires more current e.g. 20ns would require something around 30A in my application.

My question is what is a systematic way of calculating Ton term in that formula? A smaller Ton results in lower switching loss, but requires more current e.g. 20ns would require something around 30A in my application.
Hi h@ro
The answer is simple . in switching applications we should try to driver our mosfet in on/off state which will has lowest dissipation and also we should keep gate surge current as low as we can .
If we decrease it , hence it is possible that our mosfet work in linear region which is pretty dissipative region . if we allow the gate current be very high thus we'll have gate dissipations .
SO we should consider both of these parameters in our design .
By the way ton depends on what kind of application you're referring to . SMPS ? or switching amplifiers ?
Best Wishes
Goldsmith

Hi Goldsmith,

What do you mean about gate dissipations?

I think the biggest source of power loss will be in the linear region as the gate voltage rises from the gate threshold (~4v) to 10v, so the rise time over this area should be very short- Isn't it best to have as high driving current as possible, to charge the gate to 10v quickly?

The application is an H bridge motor drive- with around 100A capacity, which is why I'm concerned about power dissipation.

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