Turning the MOSFET off is important, not turning it on
In switching power supplies or any device that uses MOSFET for switching, the important issue is how to turn the MOSFET on and off.
There are many circuits for this. To turn on the MOSFET, we need to charge the input capacitor on the gate pin of the MOSFET with a voltage higher than the gate threshold voltage.
The purpose of all these circuits is to be able to quickly charge and discharge the capacitor on the cgs gate. It means that we can create a path to charge this capacitor and have a second path to discharge it.
In all circuits there is a resistance on the gate. The function of this resistor is to control the charge and discharge of the cgs gate capacitor, which also determines the switching time and does not allow high voltage to enter the gate. So the ring is not created.
If the value of the gate resistance is low, the gate capacitor cgs will charge quickly and the MOSFET will turn on quickly.
If the value of this resistance is high, the capacitor will be charged later and the switching speed will decrease
So the gate resistance is related to the switch time. Of course, it has other effects. In strong MOSFETs, in order not to create a ring on the gate, they often increase the value of this resistance, which reduces the switching speed.
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00:00 Description of the gate driver circuit
06:27 Some circuits to turn MOSFET on and off