Main PSU cutoff after filter caps using mosfets in few micro seconds any suggestions on the current approach

Im building a mosfet power amplifier with IRFP240 and 9240 in the output stage with even 7 or 10 pairs but my point of concern is to turn off the power supply after the psu bank just to cutoff when over current is detected at the source resistors either by short or any other damaging conditions. Now since Mosfet OPS is quite fast in getting damage we need fast cutoff of power supply in the order of less than 50 to 60 micro seconds. Initially thought of using photovoltaic devices to turn off the mosfets but they are not fast and finally thinking of using HCPL 3120 since its less than micro second turn of time and it also has higher current output to handle the gate charge of the mosfets which are used in the pos and neg rails. Any ideas will be very helpful.
 

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