7824

Hope somebody here can help with an electronics question. I need to
step down 30vdc to 12vdc and 24 vdc for a the stepper driver I'm working
on. I believe a 7812 and a 7824 chip will work for me. However the
specs say that Vin must exceed Vout by 3 volts. When the system is
operating that is not a problem. When I turn it off it will take a
while for the power supply cap to drop to 0 so at some point in time Vin
won't exceed Vout by 3v. Will this damage anything? If so how do I
prevent this from happening. The stepped down voltage will be used to
power small cooling fans, if that makes a difference.

Thanks,
Al