more blown chips - how to protect them?

Effect - motor does not turn
Cause - dead gate drivers
Cause - dead voltage regulator
Cause - high voltage required for high current led to spike when the current requirement reduced.

I tried to stop this happening again by putting zeners to stop the voltage at 27v but as the fuse is 10A and each zener can only handle 176mA, I would need to have far too many zeners in parallel so that the fuse blew first.

Nic and I discussed using a DC DC converter for the power supply to the chips but we could not find any with a large enough input range for a reasonable price. We decided that it would be easier to just separate the grounds and use two separate power supplies.