56 to 15 Volts Regulator for DC Motor Driving
I planned to drive gate with 100 ohm resistor in order to reduce driving current and reduce the power loss along the lm2576.


A MOSFET gate is a capacitor: to turn the FET on, a certain amount of charge must be pushed into the gate, this is called Qg or total gate charge.

The output current capability of the driver only changes how long it takes to push Qg into the gate. For example with your Qg=130nC MOSFET, at 1A drive it would switch in 130ns, and at 0.1A drive it would switch in 1.3µs.

Once the FET is turned on, the driver only consumes its idle current, which is listed as "Quiescent VCC supply current" in the datasheet, and the maximum is 340µA, which is tiny.

Thus, gate drive current only influences switching speed (and MOSFET switching losses) but has almost no influence on the current used by the MOSFET driver.

This current can be estimated as:

\$ Frequency * Qg * 2 \$

Since there are two FETs, it will use the above amount of charge (coulombs) per second, and since current is coulombs/s, you have your current.

For 25kHz and 130nC it'll be about 6.5mA. Size it up for 10mA maximum, you'll be fine.

(also your IR2106 won't work without the bootstrap caps and diode).

In fact, the gate drive current should be chosen to make the FETs switch as fast as necessary to keep switching losses down, but not faster, as this increases EMI.