# Help calculating necessary driver current to drive my power MOSFETS

#### rfengineer28

Joined Apr 28, 2021
79
Hello, I am looking to use 4 IXFH150N17T2 power MOSFETS to drive a motor in a full bridge or H-bridge configuration. I however want to know what amount of current I will need to supply the gate of the mosfet to charge and discharge its' internal gate capacitance (given I drive with a frequency of 6kHZ) its page says a gate charge of 233 nC. I would appreciate any sort of help, thanks.

#### crutschow

Joined Mar 14, 2008
34,073
It depends upon how fast you want the transistor to switch to minimize switching losses in the MOSFETs.
For example, to do this in 0.1µs, requires I = Q / t = 233nC / 0.11µs = 2.23A.

Typically this is done with dedicated half-bridge gate driver IC's the provide the large peak currents to rapidly apply and remove the gate charge.
They also typically have a bootstrap circuit to provide the necessary gate voltage of about 10V above the supply voltage to drive the top N-MOSFETs in the bridge.

Also it's necessary that the gate signals for the upper and lower MOSFETs on the same side of the bridge must be non-overlapping so that both MOSFETs are never on at the same time, otherwise there can be large, and possibly destructive, current going through both transistor during the switching time.
Some of the gate-drive IC's also provide this non-overlap function.

#### hamid641

Joined Mar 16, 2014
4
Hi, driving mosfets with a frequency of 6khz is not hard becuase your working frequency is very low.
What is your problem reality? Can you explain more?

#### crutschow

Joined Mar 14, 2008
34,073
Hi, driving mosfets with a frequency of 6khz is not hard becuase your working frequency is very low.
It isn't just the working frequency, it's how fast you need the FETs to switch that's of concern.

#### hamid641

Joined Mar 16, 2014
4
It isn't just the working frequency, it's how fast you need the FETs to switch that's of concern.
Yes, of course. It is true.

#### DickCappels

Joined Aug 21, 2008
10,127
However, the lower the frequency the slower you can switch the device on and off for a given average power dissipation...

#### rfengineer28

Joined Apr 28, 2021
79
Thank you all for taking the time to help me out. its been quite the challenge being able to find a decent driver as I have a total power supply of 120V and I need to drive a motor with my circuit.

#### hamid641

Joined Mar 16, 2014
4
Thank you all for taking the time to help me out. its been quite the challenge being able to find a decent driver as I have a total power supply of 120V and I need to drive a motor with my circuit.
Very good, what is your input power?(110AC or 220AC or...) and what is voltage of the motor and what is power of the motor?