MOSFET gate drive: What to do if incomplete conduction and oscillation occur?

Do you know the Miller platform? There is an equivalent capacitor between the MOS tube GS and GD, and the voltage across the capacitor cannot change suddenly.

Adding a switching signal at the gate can charge and discharge the capacitor.

If the resistance in series with the gate is large, the MOS tube will not be fully turned on (as shown in the figure below), but the next signal to turn off the MOS tube arrives. Why?

 This is because a larger resistor will make the gate charge and discharge current smaller, and the charging speed of the capacitor will be slower.

If the series resistance is reduced, the Vd voltage signal basically remains a square wave (as shown below), and the switching frequency is reduced, full conduction can be achieved.

 In addition to the incomplete turn-on situation, we also encounter severe ringing of the gate voltage Vgs:

 At this time, the MOSFET is no longer just in the two states of complete on and off, but repeatedly enters the high-resistance on state , causing severe heat and burning of the MOS tube.

by adding a series resistor in the drive circuit , the MOSFET gate voltage waveform oscillation phenomenon disappears.

 When R<√(L/C), it becomes an underdamped state and oscillation occurs.

When R>=√(L/C), that is, the over-damped state, the oscillation will disappear.

 However, it is best to first consider reducing the PCB lead inductance by increasing the trace width or reducing it. When the inductance cannot be reduced, an external resistor can be added to reduce the drive current.

 Some pictures and information are from 'Engineers Talk Hardware'