Mosfet

[ksoni]

I am really confused about driving mosfet. read many documents regarding this. some documents says gate current may be 2.5A, some says it may be 50mA.

what is the actual formula to calculate gate current?

I am using IRF510 (H bridge conf.) at 24V, 700 KHz.

[AScha.3 · Accepted solution]

The gate in a mosfet is (more or less) just a cap . (Here irf510, about 200pF )

So there is no current, until you switch the voltage at the gate to another level.

Then we (you) have to know, how fast this should happen , and need some current to drive the desired speed.

Usually a "gate driver" is needed, to drive the mosfet gate 0->15V and 15->0V with some current.

To limit the current (and prevent RF oscillations ) a resistor direct at the gate is needed also.

+

So for 700kHz PWM (sure, you need radio frequencies here ? ) you need a fast driver (2A...6A) and a good layout, ground plane, good decoupling .

At which max. voltage the H-bridge should work? (for 24V , need > 30V capable lo/hi-side driver (otherwise booom.)

[ksoni]

So, charge pump OR boot strap will work for such high current ?

[AScha.3]

Bootstrap will work; see a driver (i took one from mouser) like this : 2ED2778S01GXTMA1

https://www.mouser.de/ProductDetail/Infineon-Technologies/2ED2778S01GXTMA1?qs=QpmGXVUTftHsFOgntt4cHQ%3D%3D

160V max , 4/8 A drive , 30ns built in deadtime , bootstrap diode built in , about 2,50 €

- just a mini case, need good layout (!) pcb : VSON-10 , 3x3 mm !

read ds carefully, especially the "problems" , coming with stray inductance...

https://www.mouser.de/datasheet/2/196/Infineon_2ED2778S01G_DataSheet_v01_00_EN-3421193.pdf