Why does avalanche occur in power mosfet
The diagram shows the processes involved.
1
Diode breakdown
the p-n junction acting as a diode no longer
blocks voltage
3
Resistance increase
The power dissipation increases temperature, thus
increasing RB, since silicon resistivity increases with
temperature.
2
High electric field
This strong electric field causes maximum current flow in
close proximity to the parasitic BJT,
4
Sufficient voltage drop
When the voltage drop is sufficient
to forward bias the parasitic BJT, it will turn on with
potentially catastrophic results, as control of the switch is
lost.
